APL_wiki - User contributions [en]

Photo-Electric Effect

2026-05-05T14:41:55Z

Bsboggs: /* Photo-Electric Effect Module */

== Photo-Electric Effect Module ==

[http://hank.uoregon.edu/teaching-modules/photoelectric-effect/photoelectric-effect.html Photo-Electric Effect Web Page]

The Photoelectric Effect was first observed in the mid-nineteenth century. It occurs when light is shone onto a metal object, electrons are excited to the point of being emitted from the metal’s surface. Prior to the twentieth century light was believed to behave purely as a wave, which was confirmed by Young’s double-slit experiment (Wikipedia). In Classical Theory, the more intense the light is, than the light should emit electrons of higher energy, but this is not observed, and therefore poses a problem for the Wave Theory of Light. Albert Einstein suggested that light was made of particles of a discrete energy, contradicting the Wave Theory. Einstein’s theory suggested that a light particle (photon) would strike an electron of a metal object, which would then absorb the light particle. If the photon had enough energy, the electron would be emitted from the metal object. Einstein’s theory explains the Photoelectric Effect, and also differs from Wave Theory because he states that light is made of particles that deliver discrete energy, and the intensity of the light does not change the energy of the electrons that are emitted. The Einstein explanation of the Photoelectric Effect provided another example in favor of Quantum Theory, which states that energy comes in packets, and everything has a discrete amount.

Using the Photoelectric Effect, an experiment was designed to find Plank’s constant, h. This constant is one of the natural constants, to which all physical expressions can be related to in one way or another. Plank’s constant is used consistently in quantum mechanics and finding a value for h would give numerical values to many different equations.

To achieve this, an apparatus was constructed to find the stopping voltage across a phototube of which has light shone on it to create a current. A phototube is a glass tube which has two different terminals in it. The plate that has the electrons emitting from it is called the cathode, which has a larger surface area than the anode which is a pin that the electrons strike to create a current. The cathode is the plate that has the light shining on it and actually produces the effect that is being used. The stopping voltage is a potential that resists the electrons flying towards the anode. By increasing this stopping voltage to a certain point, the current will become zero across the phototube. This value is the stopping voltage for that particular frequency of light.

Using an equation that Einstein put forth to help explain the photoelectric effect, the stopping voltage can be related to the frequency of the incoming light. This equation is Ephoton = KEelectron + W where Ephoton is the energy of a photon of a certain frequency, KEelectron is the maximum kinetic energy of the incoming electrons, and W is the amount of energy it takes to emit the electrons from the metal’s surface. To relate the stopping voltage to the frequency, the above equation’s components must be substituted: Ephoton is equal to hf where h in Plank’s constant and f is the frequency of the incoming light and KEelectron is qV where q in the charge in question and V is the stopping voltage. Putting everything together and solving for V, the equation is V=hf-W. The charge is left out because each side has been divided by the value and now everything is in units of eV (electron volts). The stopping voltage and frequency can now be related by the above equation. If the stopping voltage is plotted with respect to the frequency, a linear regression will result in the slope of the graph and the y-intercept. The y-intercept will be equal to the work function of the metal and the slope of the data will be the measured value of h.

The other goal was to build the apparatus that would eventually be used to measure Plank’s constant. The apparatus was based on a schematic that was found online which gave instructions on how to build a photoelectric apparatus. Some changes were from the original schematics. These include a single power supply that could be plugged into a socket, a wider range of stopping potential, and the ability to change the intensity of the LED’s light that was emitted. These were all put together into a simple circuit and built up to create a working apparatus. [[File:Photoelectriccircuitcompairison.png|650px]]

The light that was used in the experiment was from four different LEDs varying in wavelength from an orange-yellow to a low ultraviolet. The stopping voltage for each LED was recorded seven times in the absence of ambient light. The values of the peak frequencies and a rough estimate of their standard deviation for each LED was found from their respective data sheets and converted to their respective frequency. The data was then plotted and a linear regression was fit to the data

[[File:Photoelectricdatagraph.png]].

After some error propagation the slope of the data, the calculated value of Plank’s constant, was found to be (2.56 +/- .05)*10^-15 eV*s. This value is within 40% of the accepted value of 4.136*10^-15 eV*s which is pretty close for an apparatus that was built from the ground up and under $200.

Looking at the data, the stopping voltage was measured can be trusted to be accurate. The only other thing that could have caused this inaccuracy would be the frequency of the incoming light. These values were given on the data sheets of each LED and were believed to the peak wavelength/frequency. The problem with this is that the stopping voltage was is measured is preventing the most energetic electrons from completing he circuit. And the electrons that have this energy most likely absorbed a photon of a higher frequency than the given peak value. LEDs don’t actually produce a single wavelength/frequency of light, but a range of them; only lasers produce monochromatic light. This could explain the difference between my value and the accepted value.

By playing around with my data, it was found that if the frequency is decreased or the stopping voltage is increased by 2/3, then the resulting linear fit gives a value extremely close to the accepted value. This is extremely counter intuitive, but actually makes sense. By decreasing the frequency and keeping the stopping voltage the same, it means that each photon now has more energy per unit of frequency. And by increasing the stopping voltage, but keeping the frequency the same makes each photo have more energy that before.

This manipulation of data actually proves the previous theory to be incorrect. If it is continued to be believed that the stopping voltage values to be valid, then the actual frequency of the photons must be less in order for the measured Plank’s constant to increase toward the accepted value.

There are a few things that my help the accuracy of this experiment. The first and easiest way would be to find what type of metal the cathode is made of and compare the work function that was found to that of the actual metal. If the two values are different, then setting the y-intercept to the accepted value may change the slope of the linear regression. The other thing that could be changed would be to use monochromatic light on the phototube. This light should be passed through a lens of some kind to decrease the intensity in order to protect the phototube. An error in grounding the circuit of the apparatus did come to mind, causing an artificial high stopping voltage, but when the phototube is in a dark environment the current is always zero. This shows that the circuit works perfectly and the problem is from another source.

Over all, the experiment was quite successful and even with the inaccuracy produced a solid result. The above my prove fruitful in further research or may not. It is merely a suggestion as to a jumping off point in search for a value comparable to the accepted value of Plank’s constant.

Original plans for Photoelectric Effect Apparatus [[Media:LEDphotoelectric_apparatus.pdf]]

Winter 2015 Results:

Using the same apparatus without modifications, I recorded data for 405, 468, 505, 525, 569, and 573 nm LEDs. The plot of the stopping voltage vs. frequency is shown below.

Taking a fitted slope of the plot, I find Planck's constant h = (1.83 +/- 0.2)*10^-15 eV*s. This is within the same magnitude of the accepted value of h = 4.136*10^-15 eV*s. This is a good measurement considering the different errors discussed above. An LED emits a gaussian spectrum of frequency where the peek coincides with the wavelength describing the LED. In an attempt to reduce this error I repeated the experiment with 405, 532, and 636 nm lasers. I had trouble reproducing currents because each location the laser was shined on the cathode gave different values. I tried to fix a beam on the cathode using a stand. The 636 nm laser did not produce any results so it must be under the limiting frequency. That left me with two lasers for the plot below.

[[File:Picture2.png]]

As you can see, the measurement gave me h = 2.49*10^-15 eV*s which is within 40% of the accepted value, but the error is infinite due to only using two data points. In the future we could order more lasers above the limiting frequency, but clearly the apparatus is not meant for a narrow laser beam. I would use laser diodes with beams that broaden out in a cone shape. These should fill the area on the cathode and produce more monochromatic light.

Power Supplies

2026-01-26T19:58:24Z

Bsboggs: /* Digital Power Supply */

This module will teach you how to use both analog and digital power supplies. While there will be different power supplies in the world in which you will interact, this will gain you the basic knowledge of power supplies to be able to handle any power supply you come across.

The analog power supply we will work with is the model HY3003D-3 and information can be found in this [http://www.jameco.com/Jameco/Products/ProdDS/211684.pdf data sheet] or [http://www.rapidonline.com/pdf/554308_v1.pdf user manual]. It is important to note that many different manufacturers will make the HY3003D-3 model of regulated analog power supply. While the interface might be different, the circuit diagram is the same.

The digital power supply used is the Rigol DP1308A and information can be found [http://www.rigolna.com/products/dc-power-supplies/dp1000a/dp1308a/ here], specifically under the documents tab and looking at either the [http://beyondmeasure.rigoltech.com/acton/attachment/1579/f-0021/0/-/-/-/-/file.pdf data sheet] or [http://beyondmeasure.rigoltech.com/acton/attachment/1579/f-002c/1/-/-/-/-/DP1308A%20User's%20Guide.pdf user manual].

For this module, you will need:
<ul>
<li> Rigola DP1308A digital DC Power Supply (or similar)</li>
<li> HY3003D-3 analog DC Power Supply (or similar)</li>
<li> 2 Fluke 179 True RMS multimeters (or similar)</li>
<li> An assortment of short wires</li>
<li> Resistors: 4x100ohm and 1 10kohm (or close values)</li>
<li> A breadboard (or protoboard) </li>
<li> BNC-Banana Plug Adaptor (with male BNC plug)</li>
<li> BNC Cables</li>
</ul>

This module assumes some familiarity with the [[Multimeters]] and detail will not always be explained when using these devices.

This module is part of the [[General Lab Equipment Obstacle Course]].

== Floating and Grounding ==

[[File:floatvground.png|400px|thumb|right|Diagrams for the difference between floating and grounded power supplies. Grounded power supply can not be used to boost already supplied volatages]]

It is important to first discuss the difference between a floating power supply and a grounded power supply.

[https://en.wikipedia.org/wiki/Ground_%28electricity%29 Ground] is a physical connection to the earth (ground). For American three pronged outlets, the extra little third prong will attach to ground.

[https://en.wikipedia.org/wiki/Floating_ground Floating] circuits will have a point of lowest potential, but this value could be anything relative to ground. This is what occurs for American two pronged outlets and batteries. Floating can be used to change voltages when there is already a high voltage occurring. For example boosting 1000V to 1020V, where as a grounded supply would attempt to jump 1000V directly to ground.

== Analog Power Supply ==
This section will cover use of the HY3003D-3 analog DC Power Supply (or similar). First discuss the basic nature of the power supply and then discuss the three operating modes.

=== General Analog Power Supply Information ===

[[File:Analog power supply front.jpg|400px|thumb|right|Front of a HY3003D-3 analog power supply, noting that this particular model does not state it on the front]]

The HY3003D-3 analog power supply has meaning to its name, breaking into parts HY-30-03-D-3
<ol>
<li> HY- Brand/manufacturer</li>
<li> 30- Maximum output voltage (30 volts)</li>
<li> 03- Maximum output current (3 Amps)</li>
<li> D- Display type (LCD)</li>
<li> 3- Number of outputs (3)</li>
</ol>
There are three outputs on the analog power supply-
<ol>
<li> Floating Constant 5V Output</li>
<li> Master Output</li>
<li> Slave Output</li>
</ol>

The 5V output gives out a constant 5V (surprisingly). There are three modes in which the power supply can operate: independent, series and parallel. In independent mode, the master and slave descriptions mean nothing. Only while operating in the series or parallel mode will the master control the slave. In those modes, only the controls for the master will function and it will control both supplies simultaneously.

=== Constant 5V Output ===

We will first discuss the constant 5 volt output. First to explore, we use the multimeter in resistance mode to find the internal resistance of the constant power 5V power supply. With the power off, measure the resistance from the positive terminal (red) and the negative terminal (black) of the 5V supply (far right in picture).
<ol>
<li> What resistance do you read across the constant voltage supply? Does this seem reasonable?</li>
</ol>
This value is important to know, as the internal resistance of the power supply can affect the desired output of the power supply depending on your load circuit. Now measure the resistance between the positive terminal of the constant power supply and ground (a green terminal)
<ol start="2">
<li> What resistance do you read? Does this make sense?</li>
</ol>
The 5V supply by default is a floating supply, so there should be no connection to ground. If we wanted a ground 5 Volt supply, we could connect the negative (black) terminal to the ground (green) with a wire (banana or otherwise).

=== Operating in Independent Mode ===

In the center of the panel, you will find the dial/buttons (depending on model) for the operation mode of the analog power supply. For this section, make sure that you are operating in independent mode. In this mode, the two internal power supplies are independent and can be controlled individually.

For each supply, you should be able to identify the current control knob, voltage control knob and three terminals for the voltage (red positive, black negative and green ground).
<ol>
<li> What resistance do you read from the positive terminal to the negative terminal of one of the supplies? Does this seem reasonable?</li>
<li> What resistance do you read from the positive terminal to the negative terminal of the other supply? Are they the same?</li>
<li> What resistance do you read from the positive terminal to ground? The negative terminal to ground? Does this make sense?
</ol>
Be default, both supplies are floating. We could connect the negative (black) terminal to the ground (green) with a wire (banana or otherwise) if a grounded power source was required.
<ol start="4">
<li> What resistance do you read from the positive terminal of one supply, to the positive terminal of the other supply? Does this make sense?</li>
</ol>
Even though we are in independent mode, there is still a connection between the two internal supplies. The resistance is very high, so unless the resistance of the circuit load is very high, this should be okay.
<ol start="5">
<li> What resistance do you read from the positive terminal of one supply, to the positive terminal of constant 5V supply? Does this make sense?</li>
</ol>
The 5V supply is not connected in any way to the other two supplies.

We will now move to discuss the different modes the analog power supply can operate in.

==== Voltage Supply ====

[[File:analogps.png|400px|thumb|right|Basic circuit using the analog power supply across a resistor. The multimeters should be used for ammeter and voltmeter.]]

To explore this, you will set up a very basic circuit to test the power supply. Simply put a voltage across a 100ohm resister as shown. To verify the operation of the power supply, we also want to include a ammeter in the circuit and a voltmeter across the resistor. Either power supply can be used for this section; the controls work the same for both.

With the power off, turn the current control knob all the way clockwise. This will allow for the maximal current to by supplied by the power supply. The voltage control knob should be turned all the way down by turning it all the way counter-clockwise. Turn on the power supply! Adjusting the voltage knob will change the voltage output. The display will show the voltage in Volts. Set the voltage to 7.5V.
<ol>
<li> What voltage do you read in the voltmeter? Is it the same as the reading on the power supply?</li>
<li> What current does the display read?</li>
<li> What current does the ammeter read? Is it the same as the power supply?</li>
</ol>
If you turn up the voltage too high, you will burn out the resistor! We can protect delicate circuits with the current control knob. We will be discuss current limiting below.

Replace the 100ohm resistor with the 10kohm resistor and turn the voltage knob to the max.
<ol start="4">
<li> What voltage do you read in the voltmeter? Is it the same as the reading on the power supply?</li>
<li> What current does the display read?</li>
<li> What current does the ammeter read? Is it the same as the power supply?</li>
</ol>
In this case, the load can sustain all the current and we max out at the voltage of the power supply. We will now move to discuss the using the power supply as a current source.

... turn off the power supply.

==== Current Supply ====

[[File:analogps2.png|400px|thumb|right|Basic circuit using the analog power supply across four resistors in parallel. The multimeters should be used for ammeter and voltmeter.]]

To explore this, we use a slightly different circuit. Put 4 100ohm resisters in parallel then power across the parallel circuit. To verify the operation of the power supply, we also want to include a ammeter in the circuit and a voltmeter across the resistor. Either power supply can be used for this section; the controls work the same for both.

With the power off, turn the voltage control knob all the way clockwise. This will allow for the maximal voltage to by supplied by the power supply. The current control knob should be turned all the way down by turning it all the way counter-clockwise. Turn on the power supply! Adjusting the current knob will change the current output. The display will show the current in Amps. Set the current to 0.3A.
<ol>
<li> What current do you read in the voltmeter? Is it the same as the reading on the power supply?</li>
<li> What voltage does the display read?</li>
<li> What voltage does the ammeter read? Is it the same as the power supply?</li>
</ol>
If you turn up the current too high, you will burn out the resistors! When operating in this mode is in important to know the current limit of the load you are using.

Now start adjusting the voltage knob counter clockwise, observing the voltage reading as it goes.
<ol start="4">
<li> What happens? Why is this?</li>
</ol>
This idea is the basics behind the current limiting function of the power supply. The current knob can be set to the desired maximal current and then the voltage can be varied.

Return the current to zero and the voltage to the max. Replace the parallel circuit with a 10kohm resistor.
<ol start="5">
<li> What happens if you try to increase the current now? Why is this?</li>
</ol>
Each individual supply can only give 30V. We will discuss how to get more voltage by operating in the series mode.

...Turn off the power supply

==== Current Limited Protection Mode ====

These power supplies can be operated in a current limited mode in order to protect the load from high currents. This section will describe how to set a current limit before the power supply has been connected to the load.

With the supply off and nothing connected to the power supply, turn the current control all the way to the max and the voltage control to the minimum. Turn on the power. We want to adjust the adjust the voltage control to the voltage we will be using (or the maximum voltage). At this point set it to 10V. '''Important:''' Turn the current control back to all the way to minimum. Now connect the positive and negative terminal with a thick banana wire. We can now adjust the current to our desired limit with the current control knob. Set it to 0.3A. Unplug the banana wire and turn the voltage all the way down. Now attach the parallel circuit from the current source section. Start upping the voltage now that the circuit is connected.
<ol>
<li> What happens? Why is this?</li>
</ol>
This is the safest and most effective way to protect a circuit before it is ever connected to the power supply.

...Turn off the power supply

=== Operating in Series Mode ===

[[File:analogpsseries.png|400px|thumb|right|Note that for series mode, we use the negative (black) terminal for the slave and the positive (red) terminal of the master.]]

Switch the center switch to series mode. This will vary depending on the model you are using. In this mode the two supplies will become linked in series allowing for a greater voltage output.

With the power off, connect the negative terminal of the slave to one end of a 10kohm resistor and the positive terminal of the master to the other end of the resistor. This will connect across both supplies. Adjust both slave knobs and the master's current control to the maximum value (clockwise) and the master's voltage knob to zero.
<ol>
<li> Which supply mode are we operating in (voltage or current)?</li>
</ol>
Turn on the power supply. Start adjusting the master voltage and observe the voltage displays.
<ol start="2">
<li> What do you notice about the voltage displays?</li>
<li> What is the maximal voltage you can get?</li>
<li> What do you think the voltage across the resistor is?</li>
</ol>
Set the voltage on the master display to 5 volts. Get your multimeter handy and get ready to measure some voltages.
<ol start="5">
<li> Measure the voltage across the resistor, what it is?</li>
<li> Measure the voltage from the positive terminal of the master to the negative terminal of the master, what it is? Does this make sense?</li>
<li> Measure the voltage from the positive terminal of the master to the positive terminal of the slave, what it is? Does this make sense?</li>
<li> Measure the voltage from the positive terminal of the master to the negative terminal of the slave, what it is? Does this make sense?</li>
<li> Measure the voltage from the positive terminal of the slave to the negative terminal of the slave, what it is? Does this make sense?</li>
</ol>
Each supply still creates its individual voltage, and the total of those can be utilized by treating them as one supply with the master's positive terminal and the slave's negative terminal. The thing to remember is that the total voltage will be the sum of the displays.

Turn down the voltage to zero. Now remove the 10kohm resistor from the circuit and replace it with the 4 100 kohm resistors in parallel. Now make the voltage across the resistors 4 volts (2 volts on each display). Adjust the slave voltage knob all the way down and back up. Then do the same with the slave current control.
<ol start="10">
<li> What happens when the slave voltage is adjusted?</li>
<li> What happens when the slave current is adjusted?</li>
<li> Why do you think it works this way?</li>
</ol>
The master completely controls the voltage in this mode, so the slave voltage control has been disabled. The slave current control can still be used to limit the current, but the master still continues to operate. Make sure the slaves controls are both set to maximum. Now adjust the master current control.
<ol start="13">
<li> What happens when the current control kicks in?</li>
</ol>
In this case, the master current control will also control the slave's current as well as the voltage. With this in mind, the series power supply can and should be operated using only the master controls. If a current source was wanted, everything can be done with the master controls.

=== Operating in Parallel Mode ===

Operating in parallel mode allows for a high current output. The power supplies will be linked in parallel with each other. Again in this case, the slave controls should be opened to the max, and all adjustments to the current or voltage should be down with the master controls. The load can go across either the slave or master terminals, but it is suggested to use the master terminals.

In this mode, the maximum voltage remains 30V, but the maximum current will be 6A. As this is a high current that would require many resistors in parallel to get the current without burning out the resistors, we do not test this limit here.

In this mode, the parallel supply can be used in either current or voltage limiting mode using the techniques given above.

== Digital Power Supply ==
This section will cover use of the Rigol DP1308A digital DC Power Supply (or similar). First discuss the basic nature of the power supply and then discuss the display modes and several operation modes of the power supply.

=== General Digital Power Supply Information ===
[[File:Digital Power Supply Front.jpg|400px|thumb|right|Front of a Rigol DP1308A digital power supply]]

Rigol DP1308A digital DC Power Supply doesn't seem to have as clear of a meaning to its specification number. There are three outputs on the digital power supply-
<ol>
<li> Independent 6V/5A Output (red)</li>
<li> Common 25V/1A Output (yellow)</li>
<li> Common -25V/1A Output (green)</li>
</ol>

The 6V supply is isolated from the from the other two outputs for pure independent sources if needed. The two common port supplies have the same reference point for zero voltage. One supply will give positive voltages from that zero, while the other goes more negative. This can be considered the two supplies being connected in series as above for the analog circuits.

Again all the outputs are floating by default. There is a ground terminal on the front that can be used to ground the terminals if desired. Remember that if this is to be used to connect to the negative terminals as marked on the power supply.

=== Front panel controls ===
[[File:Digital controls1.jpg|250px|thumb|right|Section of the panel for selecting power supplies and turning them on/off]]

At first changing the voltage and current for the supplies can seem odd and cumbersome, so we will first familiarize ourselves with the controls. Directly to the right of the display, you'll notice the buttons shown to the right. With these controls, you are able to select which supply you will be controlling with the +6V, +25V and -25V buttons. With the power on, try selecting the different outputs.
<ol>
<li> Looking at the display, how can you tell which one is active?</li>
</ol>
Above the output selection are the buttons for turning on/off all the supplies at the same time. Press the All on button.
<ol start="2">
<li> What happens? Why do you think they would prompt this?</li>
</ol>
Select cancel using the button directly under cancel on the display. Typically turning all the supplies on is not the best idea unless you are sure everything is setup correctly. Lets go ahead and select the 6V supply. Now press the on/off button directly below it to turn it on.
<ol start="3">
<li> How can we tell the supply is turned on?</li>
<li> Is there more than one way to tell?</li>
</ol>
Go ahead and turn off the 6V supply. We will move to discuss how to set the voltages and currents for the outputs. You should notice at the bottom of the display the words Volt, Curr, O.V.P. and O.C.P.
<ol start="5">
<li> Which one is light up? What do you think this means?</li>
</ol>
The buttons below each of those will allow to to set the voltage, current, over voltage protection and over current protection, respectively.
[[File:Digital controls3.jpg|400px|thumb|right|Panel section for setting values]]
If we want to set the voltage, there are two ways to do it:
<ul>
<li> Adjusting the value with the cursor.</li>
<li> Setting the value directly.</li>
</ul>
First, we will use the cursor to set it. Select Volt below the display to set the voltage. You will notice a little white box in the lower smaller voltage. The location of the box can be moved using the left and right arrows on the grey dial to the right of the display. The value of the box can be shifted up and down using the up and down arrows. Try setting the voltage to 0.5V and 1A. Remember that to switch to current, you'll need to select it using the display.

Now we use the number pad to set the voltage and current. This is done by typing the value into the keypad, then selecting the units you wish to use. To select the units, you can either use the grey buttons that were used to adjust previously. Or using the buttons below the display. Try setting the voltage back to 6V and current in 5A.
<ol start="6">
<li> Do you have to have the current selected to change the current with this method?</li>
<li> Which method do you prefer to use?</li>
</ol>

We will discuss the over protection functions later, but for now know that they can be set in the same manner as for the voltage and current.

=== Display Modes ===

There are four display modes available for the Rigol digital power supply.
<ul>
<li>General display mode (default when turned on)</li>
<li>Focus display mode</li>
<li>General waveform display mode</li>
<li>Focus waveform display mode</li>
</ul>

The two categories that change are the general/focus and waveform display. The button to switch to focus mode is at the lower right of the display (looks like a magnifying glass), press it to see what happens.
<ol>
<li>Describe what is different.</li>
<li>Can you change which channel is focused on?</li>
</ol>
This power supply has a timing mode that can be used to switch the voltage/current after a set amount of time. The focus mode displays the next current and voltage settings when using timing. We will discuss timing later.

On the right side of the control panel you will see the "Wave Disp" under the number pad. Press it now. Turn on the current channel, then set the voltage to 10V.
<ol start="3">
<li>What do you notice?</li>
</ol>
Change the voltage to another value and wait a few seconds.
<ol start="4">
<li>How often does this display update?</li>
</ol>
Now switch to a different channel. This channel will now be the focus of the display. In this mode it is easy to see which channel is currently being set.
<ol start="5">
<li>Is this channel in waveform display?</li>
<li>What do you think the general waveform display looks like right now?</li>
</ol>
Return to general mode by pressing the focus button again.
<ol start="7">
<li>Is it what you expected?</li>
</ol>
Depending on your application, some of the channels will remain fixed, while others can be set on a timer and which one you want to watch is important.

Now that you have stepped through the different display settings, you should be able to use the one that is most applicable to your application!

=== Voltage Supply ===
[[File:Digitalps.png|250px|thumb|right|4 100ohm resistor is parallel as load attached to the 6V channel of the digital power supply]]

We will now explore using this power supply as a voltage source. For our load we will use the 4 100ohm resistors in parallel. We will use the 6V channel and attach the load as shown in the figure. You can have the display set to which ever mode you want. Turn on the 6V channel. Set the Voltage to 5V.
<ol>
<li> What is the current currently set to? (if not 5A set to 5A)</li>
<li> What is the voltage output?</li>
<li> What is the current output?</li>
<li> What is the power output?</li>
</ol>
Change the voltage to a few other values and witness the changes.

These resistors cannot take too much current before they start to burn. As was done for the analog supply, we will now examine current protection for our load. For now set the voltage equal to zero before moving on.

==== Current Limited and Over Current Protection ====

There are two ways to protect the circuit from too much current. The two ways are current limiting and over current protection (OCP). Current limiting will hold the voltage below a certain value, while the OCP will shut off the channel completely.

Set the current value to 0.1A. Now set the voltage to 1V.
<ol>
<li> What is the voltage output?</li>
<li> What is the current output?</li>
<li> What is the power output?</li>
</ol>
Now set the voltage to 5V.
<ol start="4">
<li> What is the voltage output?</li>
<li> What is the current output?</li>
<li> What is the power output?</li>
</ol>
As with the analog supplies, the highest the current will go is what we have set the current. This is current limiting.

Now set the voltage to zero and the current to 5A. Press the OCP button below the display. By default this is set to off and 5.5A. Set the OCP. to 0.1A. Then press the OCP button to turn on OCP. Now set the voltage to 5V. If you are using keypad entry for changing voltages, you will need to press the voltage button below the display first before setting the value.
<ol start="7">
<li> What happened?</li>
<li> What is the output on the display?</li>
</ol>
You will notice that not only did it turn off the channel, but it also turned off OCP. Try turning OCP back on.
<ol start="9">
<li> What needs to happen before you can turn OCP back on?</li>
</ol>
You typically want to reset your voltage and current before you turn the channel on again.

Before moving on, you want to make sure that OCP is off.

=== Current Supply, Voltage limiting and Over Voltage Protection ===

To have a current supply, it follows the same as for the analog supply for a current supply. You will set the voltage to maximum and then set the current to the desired amount.

Make sure you start with the channel off. We will use the setup from the voltage supply section. Set the voltage to 6V and current to 0A. Now turn on the channel. Set the current to 50mA.
<ol>
<li> What is the voltage output?</li>
<li> What is the current output?</li>
<li> What is the power output?</li>
</ol>
Now set the current to 0.3A
<ol start="4">
<li> What is the voltage output?</li>
<li> What is the current output?</li>
<li> What is the power output?</li>
</ol>
You will not get the 0.3A you want as the supply has now been voltage limited. The same idea holds that the highest voltage you will get for a given current is set by the voltage input.

Now set the Over Voltage Protection to 3V and then turn it on.
<ol start="7">
<li> Is this any different than when OCP was used?</li>
</ol>
Remember that if the channel is shut off for this reason to reset your current to zero before turning the channel back on and then enabling the OVP.

Note! You can set both OCP and OVP at the same to protect from high voltages and currents at the same time!

=== Series mode (multiplexed) ===

This digital power supply has two of the channels automatically in series mode. The yellow +25V channel and green -25V supply have a common port. To explore this we will use the multimeter to test the voltages at different points of the output channel. Set the yellow channel to 5V and the green channel to 12V and turn on both channels. Use the multimeter to answer the following questions:
<ol>
<li> What is the voltage from the common port (black) to the output of the 25V channel (red to the left)?</li>
<li> What is the voltage from the common port (black) to the output of the -25V channel (red to the right)?</li>
<li> What is the voltage from the output of the -25V channel to the output of the 25V channel?</li>
</ol>
In this case we can separately change the voltage for each channel. There is no master power supply.

==== Tracking ====
We can setup either supply to control the output of the other. This is done with the track button. With the yellow channel (+25V) set to 5V and the green channel (-25V) set to 12V, select the green channel. Turn on both channels and press the track button on the right side of the panel. The display will prompt that this will change the output, hit OK.
<ol>
<li> What is the voltage output of the green channel?</li>
</ol>
Try changing the voltage of the -25V channel.
<ol start="2">
<li> What happens?</li>
</ol>
Now change the voltage of the +25V channel.
<ol start="3">
<li> What happens?</li>
</ol>
This has made the yellow channel the master and the green channel the slave. Alternatively, the green channel is tracking the yellow channel. Now select the yellow channel and hit the track button. It'll prompt you about the voltage changing, hit OK. The yellow channel is tracking the green channel now.
<ol start="4">
<li> How can you tell?</li>
</ol>
If you press track again, the channel with stop tracking.

Using the tracking is the best way to control the power supply between 0 and 50V using the two channels in series.

=== Timing mode ===

Timing mode allows for you to set up the power supply to change the voltage and current at set points in time. To see how this is done, we will go through a sample timing scheme. We will use the 4 100ohm resisters in parallel as our load and the +25V supply. Press the utility button on the right side of the panel. Then press TimerSet under the display. You should see the display shown to the right.

[[File:timing.jpg|400px|thumb|right|Display for timing when first entered.]]

With the buttons below the display, you can select which channel you will be modifying. Select +25V. The left side of the display that is currently empty will later show the graphs of the voltage and current as a function of time. The right side is where the values will be set. There are 5 steps that the timing can do. For each step you can set the voltage, current and duration of the step. The "Left" column is used for specialized timing and will not be discussed in this module. If it needs to be used check the user manual for the power supply. The arrows can be used to select which value you are setting. To set a value, the keypad must be used. Once the value is set, it will automatically step to the next box. Input the follow settings:
<ul>
<li> Step 1- 10V, 6A, 20s</li>
<li> Step 2- 5V, 6A, 20s</li>
<li> Step 3- 50mV, 6A, 20s</li>
<li> Step 4- 25V, 0.5A, 20s</li>
<li> Step 5- 25V, 50mA, 40s</li>
</ul>
It should look now look like the 2nd image in this section. The left side now should visually show the settings and durations of each of the steps.
<ol>
<li> How is the duration represented compared to the total time?</li>
</ol>

Now press exit to return to the normal display. Now change the display to focused waveform on the 6V channel. Finally turn on the channel, press the timer button, hit OK, sit back and record the data values.
<ol start="2">
<li> Draw the voltage, current and power as a function of time as you see it on the display.</li>
</ol>
[[File:timing2.jpg|400px|thumb|right|Display for timing after values have been entered.]]
You will notice that it turns off the channel at the end. Press timer while the channel is off, then turn on the channel.
<ol start="3">
<li> What happens?</li>
</ol>
Often timing can be used to run a circuit start to finish. At this point feel free to play with the timing, but be careful to not burn out your resistors! To do this set the OCP to 0.5V, the voltage to zero and the current to zero. Now turn on the channel, activate OCP and then hit the timer button.
<ol start="2">
<li> Draw the voltage, current and power as a function of time for your new parameter set.</li>
</ol>

Now you can set basic changes in voltage as a function of time. Function generators will typically be used when a repeating change needs to be used. Usage of them can be found The module is available [[Function Generators and Oscilloscopes|here]].

=== Other Functions ===

There are a few more settings and modes that can be used with the digital power supply such as
<ul>
<li> Storing and recalling system parameters </li>
<li> USB, LAN and GPIB interfaces</li>
<li> U disk store</li>
<li> Remote control via Web or commands</li>
<li> Help function</li>
<li> Utility settings</li>
</ul>
For more information on these settings and modes, please refer to the [http://beyondmeasure.rigoltech.com/acton/attachment/1579/f-002c/1/-/-/-/-/DP1308A%20User's%20Guide.pdf user manual].

Power Supplies

2026-01-26T19:57:00Z

2023-11-30T19:56:42Z

Bsboggs:

Electrical Setup

Optics Obstacle Course

2023-11-28T22:36:48Z

Bsboggs: /* Activities */

== Permanent Materials (located on optical breadboard or in storage cabinet): ==
[[File:OOC.jpg|600px |right ]]
- Optics cleaning materials 
- Helium Neon laser 
- 4 mirrors 
- [[Media:Lenskit1.jpg | Telescope lens pair (Newport KPX.097 and KPX.085)]] 
- 3 irises and a pinhole 
- Quarter waveplate @633 
- Half waveplate @ 633 
- [[Media:CM1-BS013.pdf | Non-Polarizing Beam Cube]] 
- [[Media:QryYg.jpg | Polarizing Beam Cube]] 
- [[Media:DET110-SpecSheet.pdf |Thorlabs DET 110 photodetector]] 
- [[Media:DET10A-Manual.pdf | Thorlabs DET 10A photodetector]] 
- [[Media:DET210-SpecSheet.pdf | Thorlabs DET 210 photodetector]] 
- Various optomechanics (mirror mounts, lens holders, baseplates, etc) 
- Beam block/alignment tools 
- Hecht ''Optics'' book

=== Materials to borrow when necessary ===
- Oscilloscope 
- [[Media:SRS_CHopper.jpg | Chopper]] 
- [[Media:Powermeters.png | Power meter]] 
- Extra optics as needed 

=== Activities ===
You should have the necessary tools at your disposal to complete the following. Instructions are intentionally a bit sparse to encourage thoughtful exploration of the system. The left-hand-side of the optical breadboard is permanent storage for the optics (leave the bases and post holders where they are), and the right-hand-side contains optomechanics you can use in positioning elements in the 'sandbox' area. 
Make sure that all the optical components (waveplates, beamcubes, etc.) are designed to work at your laser's wavelength. 
* '''CLEAN UP THE OBSTACLE COURSE SETUP AFTER USE''' 
Keep a journal of your activities, results and answers to any questions asked in the activities below. You will use this for your brief write-up. If any step in the activities below is unclear or you do not completely understand something ask the instructor or TAs for help '''before moving on'''. 
# Read laser safety, optics common sense, optics hardware info (pages 1-19 of the ebook "''Laboratory Optics - A Practical Guide To working in an Optics Lab''"). Throughout this exercise, please make an effort to never allow the laser or any reflection/retroreflection leave the boundary of the optical table
# '''Very Important: Get a demonstration/lecture from the instructor or TAs on the proper handling and cleaning of optics. Do not proceed until this is done.'''
# Read pages 20-31 of ''Laboratory Optics'' ebook.
# Read about polarization in the Hecht ''Optics'' book. [[Media:Optics_polarizer.jar | Download and run this applet to explore polarizers]]. Use two mirrors to set the beam height to a level 4” above optical table. Is the light polarized? If not, polarize it, aligning the axis of polarization vertically.
# Read about Brewster's angle in Hecht. [[Media:Waves_brewster.jar | Download and run this applet to explore Brewster's angle.]]
# Use a glass microscope cover slip on a rotation stage and the laser horizontally polarized to measure Brewster's angle (based on power and/or polarization measurements). From the measured Brewster's angle calculate the cover slip's index of refraction. Calculate the Brewster's angle assuming a glass index of refraction of 1.5. Does your measured Brewster's angle agree?
# Read sections 3.1-3.5 of ''Laboratory Optics'' ebook.
# Use mirrors to pass beam through two irises (or two beam alignment cards), aligned along a row of holes on the table. You now have a level beam with set polarization that is pointing in a known direction. This is an appropriately initialized optical setup.
# Read sections 4.1-4.3 of ''Laboratory Optics'' ebook.
# Measure the power of the beam using two techniques: a power meter; and the Thorlabs photodetector and an oscilloscope (for this second method, you'll need to look up the responsivity curve on the detector datasheet). These two measurements should be in reasonable agreement. If they're not consult with the instructor or TAs for help. Make sure you're operating the power meter correctly. That is, use the correct power-meter detector head for your wavelength and set the power meter to your specific wavelength. Also make sure you're using an appropriate (electrical) power supply (rated at the correct voltage/current) for the power meter.
## If the photodetector appears to be saturating (detector's output voltage at spec'd maximum), you will need to use neutral density filters to reduce the power.
## For insight to what the numbers on the filters mean, measure the Optical Density (OD) of the blue laser goggles at the HeNe wavelength <math>P_{out}=P_{in}\,10^{-OD}</math>
Read about half and quarter waveplates (also called retarders in Hecht's ''Optics'') before doing the following:
[[Media:Em wave polarization simulation.jar | Download and run this optical polarization applet.]] Try to create circular and elliptical polarization. If you have trouble ask the instructor to help. 
## How does vertically polarized light interact with the polarizing beamsplitter cube? Use the half waveplate to rotate the axis of polarization to be horizontal. Now what happens with the cube? Finally, rotate the axis of polarization to be 45 degrees from vertical
##Align the axis of the quarter waveplate so that the beam is circularly polarized. How do you know it’s circular and not elliptical?
#Build a 1:2 telescope to expand the beam
# Use a 200 micron pinhole, the photodiode and a translation stage (scan the beam in the transverse direction) to measure the 1/e width of the collimated laser beam. See here for info on using translation stages - https://june.uoregon.edu/mediawiki/index.php/How_to_Read_a_Micrometer.
## Draw a simple ray diagram to estimate the magnification you expect for the two supplied lenses
## Be sure to position the lenses so the beam is centered (hint: you should do this by observing the output beam location, not merely by eyeballing where the beam hits the lens)
## Ensure collimation after second lens. Does the magnification match your prediction?
# Place a (suitably chosen - ask instructor) pinhole at the focus of the telescope. Read about Gaussian Laserbeams in ''Hecht'' pages 617 to 619. Pay especial attention to the concepts of spot size and Rayleigh range. What is the spot size (take measurements)? What is the Rayleigh range (take measurements)?
# Focus light onto a small (silicon) photodiode (e.g., Thorlabs DET 10A). Use a chopper in between a two-lens telescope and an oscilloscope to measure the [https://en.wikipedia.org/wiki/Rise_time rise time] of the small diode. Do the rise time measurement again with a larger (silicon) photodiode (e.g., Thorlabs DET 110). Compare the two measured rise times. Are they different? Can you explain? Note: When using the chopper, use a short focal length converging lens to focus the beam (to a small spot) in the plane of the chopper and another lens to re-collimate the beam after the chopper. If this doesn't make sense ask the TA or instructor to explain.
# Use a polarizer and a quarter waveplate to create a "[https://www.rp-photonics.com/spotlight_2010_06_09.html poor man's]" optical isolator. Why would this be useful?
# Use a polarizing beamsplitter and a quarter waveplate to make a (slightly) better optical isolator.
# Discuss the drawbacks of the previous two types of isolators. Read about an even better type of [https://www.rp-photonics.com/faraday_isolators.html isolator] that employs a Faraday rotator.
# Use a mini fiber-coupled spectrometer to obtain the center wavelength and an upper bound on the linewidth of the laser. Have a discussion with the TA or instructor about the concept of linewidth.
# Read sections 5.1-5.4 of ''Laboratory Optics'' ebook.
# Read about a Michelson interferometer in Hecht ''Optics''. [[Interferometers | See this page for more infomation]]. Build a Michelson interferometer (with a non-polarizing beamsplitter) and measure the laser wavelength. Now use the Michelson to measure the index of refraction of 1) a glass microscope slide and 2) an unknown optical material (ask instructor). (Leave the Michelson set up for next activity)
# Read about coherence theory in Hecht's ''Optics'' Chpts 12.1, 12.2 and 12.3. Measure the laser's coherence length (ask instructor or TA for help).
# Fabry-Perot (FP) cavities: Read about FP cavities in ''Hecht'' sections 9.6 and 9.6.1. Pay attention to the concepts of Finesse, Free Spectral Range (FSR) and Resolution.
## Use the [http://www.gwoptics.org/finesse/ ''Finesse/Luxor''] software package (already downloaded and located in the user's home directory on lab computer ''hank'' - run Luxor.jar in the FinesseLuxor directory) to simulate a FP cavity. Explore how the cavity Finesse, FSR and Resolution depend upon the mirror reflectivity and mirror spacing.
## Assume the cavity mirrors are planar with a power (not amplitude) reflectivity of 90% (R = 0.9). Calculate the cavity finesse assuming an on-axis light beam.
## Construct a plane-mirror Fabry-Perot with a Free Spectral Range (FSR) of 500MHz and a Finesse >= 20. What is the cavity resolution?
## Construct a plane-mirror Fabry-Perot with a Free Spectral Range (FSR) of 1 GHz and a Finesse >= 20. What is the cavity resolution?
## Is the finesse of your cavity equal to the calculated finesse? If not, why?
## What are the practical limits on the achievable finesse? In other words, what is the limit of achievable cavity resolution? 
#Aberrations: Read ''Hecht'' Chpt 5.1, 5.2, 5.2.1, 5.2.2, 6.3.1, 6.3.2, (stopping at page 272). Pay especial attention to the concepts of "diffraction-limited", "aspherical surfaces", "spherical surfaces", "optical axis", "aberrations", "paraxial rays", "Gaussian optics", "Seidel aberrations", "spherical aberration", "circle of least confusion", "coma", "astigmatism", "field curvature", "distortion", "chromatic aberrations".
## What type of lens surface will take all rays falling on its surface and focus them to the same point?
## How can a spherical lens be used so that the Seidal aberrations are minimal?
## [[Media:spherab.cdf | Download and run this Optica-based CDF file to demonstrate the effects of spherical aberration.]]
## [[Media:Seidel_Aberrations.nb | Download and run this ''Optica'' notebook (detailing Seidel aberrations in ''Mathematica'' on lab computer hank)]]

- Debrief with the instructor concerning your efforts, observations and measurements of the obstacle course. 

After you finish, please return items to the storage location and clear the 'sandbox' area. 
* '''CLEAN UP THE OBSTACLE COURSE SETUP AFTER USE'''

How to Read a Micrometer

2023-11-28T22:32:36Z

Bsboggs:

[[File:How to Read a Micrometer.png|800px|left|thumb | Newport SM25 Vernier Micrometer]]

How to Read a Micrometer

2023-11-28T22:30:51Z

Bsboggs:

[[File:How to Read a Micrometer.png|800px|left|thumb | Newport SM25 Micrometer Screw]]

How to Read a Micrometer

2023-11-28T22:24:55Z

Bsboggs: Created page with "left"

[[File:How to Read a Micrometer.png|800px|left]]

File:How to Read a Micrometer.png

2023-11-28T22:22:03Z

Bsboggs:

APL wiki:Community portal

2023-11-28T22:21:29Z

Bsboggs: /* Projects and Modules */

Welcome to the University of Oregon, Department of Physics, Advanced Projects Lab's Wiki.

To see our main website visit [http://june.uoregon.edu Advanced Projects Lab].

== Projects and Modules ==
[[File:APL.jpg|650px|right]]
[[Advanced Projects]]

[[Teaching Modules]]

- ''[[General Lab Equipment Obstacle Course]]''

- ''[[Basic Machining Obstacle Course]]''

- ''[[Optics Obstacle Course]]''

- ''[[Fiber-Optics Obstacle Course]]''

- ''[[Electronics Obstacle Course]]''

- ''[[Digital-Electronics Obstacle Course]]''

- ''[[Make and Test a Semiconductor Device]]''

- ''[[Permittivity and Permeability of Materials Obstacle Course]]''

- ''[[Vacuum Technology Obstacle Course]]''

- ''[[Scientific Python Primer]]''

- ''[[LabVIEW Primer]]''

- ''[[Media:Taking,_Storing,_Transferring_and_Presenting_Data.pdf| Taking, Storing and Presenting Data]]''

- ''[[How to Make a Printed Circuit Board (PCB)]]''

- ''[[How to Test Transistors and FETs]]''

- ''[[Operating Fusion Splicers and Preparing the Fiber]]''

- ''[[How to Coat Optical Fibers]]''

- ''[[How to Read a Micrometer]]''

=== Useful Links: ===

[http://www.rp-photonics.com/encyclopedia.html RP Photonics Encyclopedia]

[http://www.newport.com/Tutorials/979935/1033/content.aspx Newport Tutorials]

=== LaTeX Help: ===

[[Working with TeX Equations]]

[http://en.wikipedia.org/wiki/LaTeX LaTeX - Wikipedia]

[[Media:Lshort.pdf |The Not So Short Introduction to LATEX]]

=== Wiki Markup Help: ===

[http://en.wikipedia.org/wiki/Help:Cheatsheet Help:Cheatsheet]

[http://en.wikipedia.org/wiki/Help:Wiki_markup Help:Wiki markup]

[http://en.wikipedia.org/wiki/Wikipedia:Extended_image_syntax Wikipedia:Extended image syntax]

[http://www.mediawiki.org/wiki/Help:Tables Help: Tables]

=== CDF (Computable Document Format) Help: ===
''(Note - The Wolfram CDF player for Linux currently doesn't support the browser plugin)''

[http://www.wolfram.com/cdf-player/ Get the Wolfram CDF Player]

[http://en.wikipedia.org/wiki/Computable_Document_Format CDF - Wikipedia]

[http://www.mediawiki.org/wiki/Extension:WolframCDF#Usage How to include CDF files on wiki pages]

Electronics Obstacle Course

2023-05-05T17:22:29Z

Bsboggs: /* Optoelectronics */

== Permanent Materials (located in the electronics area): ==
[[File:Electronic_station.jpg|right|500px]]
- power supplies 
- [[Media:DG1022.pdf|function generators]] 
- [[Media:DS1102E.pdf|oscilloscopes ]] 
- [[Media:Fluke_179.pdf| Fluke 179 multimeter (MM)]] 
- [[Media:CX-920A.pdf| capacitance meter]] 
- [[Media:PB-505.pdf|electronic proto-boards]] 
- wire, resistors, capacitors, inductors, diodes, Op-Amps, other ICs 
- photodiodes (PDs), light-emitting diodes (LEDs), laser diodes (LDs) 
- soldering equipment and supplies

=== Materials to borrow when necessary ===

- ''The Art of Electronics (AoE)- 3rd Edition'', Horowitz & Hill 
- inductance meter 
- voltage supply
- Red LD module
- Optical power meter
- Spectrometer

[[File:Symbols.png|frame|right|Electronic Component Symbols|200px]]

=== Activities ===

* If you have zero electronic training or experience read chapters 1-6 of Keith Brindley's eBook ''Starting Electronics''.
* If you have a little experience with electronics proceed and consult ''Starting Electronics'' or ''The Art of Electronics'' as needed. 
* '''CLEAN UP THE OBSTACLE COURSE SETUP AFTER USE - PUT BACK ELECTRONIC COMPONENTS IN APPROPRIATE PLACES AFTER EACH ACTIVITY'''
* Keep a journal of your activities, results and answers to any questions asked in the activities below. You will use this for your write-up.

==== Resistor & Capacitor Basics ====

* Read Chpt 1 of AoE. 
[[File:Fluke_179.jpg|right|100px| thumb| multimeter]]
# With a MM measure the resistance of five 100 Ohm resistors. Do they fall within the specified tolerance?
## What is resistance? Can you provide an analogy based on water flowing through pipes?
## Describe physically a resistor.
## Is energy stored in a resistor or dissipated as heat? Can you provide an explanation of the basic physical processes?
## What is the resistance of two 100 Ohm resistors in series? How do resistors in series add?
## What is the resistance of two 100 Ohm resistors in parallel? How do resistors in parallel add?
## How might the MM measure the resistance?
## What can you say about the "internal" resistance of the MM in resistance measurement mode?[[File:Pb-505.jpg|right|100px|thumb|proto-board]]
## Using a proto-board and one of the 100 Ohm resistors put 2.5VDC '''across''' the resistor. Calculate the current. Use the MM in ammeter mode to measure the current. Are the calculated and measured values close? Does the power applied to the resistor fall within the power rating of the resistor? What is power? What could happen if you applied too much power to the resistor?
## What is current?
## How might the MM measure current?
## What can you say about the "internal" resistance of the ammeter used in the measurement of the current?
## How do the MM wire leads effect these measurements?
## Could you measure the resistance of a 1cm length of copper wire with the MM? Why?
# Put 150mA of DC current '''through''' a 10 Ohm resistor.
## What power is being applied to the resistor? Calculate the voltage '''across''' the resistor. With the MM measure the voltage across the resistor. Are these values close?
##What is voltage?
## How might the MM measure a voltage?
## What can you say about the MM's "internal" resistance when it measures a voltage?
# With a function generator put a 5VAC (peak-to-peak) sinusoidal voltage at frequencies of 50, 500 and 1000 Hz '''across''' a ~ 5k Ohm resistor.
## Using the MM in voltage mode measure the AC voltage. Does it vary with frequency?
## Using the MM in current mode measure the AC current. Does it vary with frequency? 
# Measure the capacitance of five 0.1 <math>\mu</math>f unpolarized capacitors. Do they fall within the specified tolerance?
## What is capacitance? Describe physically a very simple capacitor.
## How is energy stored in a capacitor?
## What is the difference between unpolarized and polarized capacitors?
## What is the capacitance of two 0.1 <math>\mu</math>f capacitors in series? How do capacitors in series add?
## What is the capacitance of two 0.1 <math>\mu</math>f capacitors in parallel? How do capacitors in parallel add?
## How might the capacitance meter measure the capacitance?
## Using a proto-board apply 2.5VDC '''across''' an 0.1 <math>\mu</math>f capacitor and 100 Ohm resistor in series. Using a MM measure the voltage '''across''' the entire capacitor + resistor series network. Measure the voltage across the capacitor only. Measure the voltage across the resistor only. Explain the measured voltage across the resistor.
## Now apply a 2.5VAC sinusoidal voltage '''across''' the capacitor + resistor network at 50, 500 and 1000 Hz.
## What's the voltage across the resistor for 50, 500 and 1000Hz?
## What's the voltage across the capacitor for 50, 500 and 1000Hz?
## How does the voltage across the capacitor as a function of frequency compare to the voltage across a resistor as a function of frequency? [[File:Voltagedivider.gif|right|100px]]
# Build a network of two (possibly different valued) resistors that takes an input voltage of 5VDC and produces an output voltage at 2.5VDC.
# Build a network of two (possibly different valued) resistors that takes an input voltage of 5VDC and produces an output voltage at 1.25VDC.
# Build a network of an <math>\mu</math>f capacitor and a 100 Ohm resistor in series.
## Apply a 1VAC sinusoidal (input) signal to the capacitor at 100, 1000, 5000, 10000, 15000, 20000, 25000 and 50000 Hz and measure the (output) voltage between the capacitor and the resistor for each frequency.
## Plot as a function of frequency. What can you say about the frequency dependence of the ratio of output to input voltage?
## You've just built three very useful circuits called voltage dividers. Would a voltage divider containing only resistors work for AC voltages? If you're unsure, try it. Would a voltage divider containing at least one capacitor work for DC voltages? Again, if you're unsure, try it. 
# Now, apply a 1V 10Hz square pulse to a 500 Ohm resistor and an 10 <math>\mu</math>f capacitor in series.
## Using an oscilloscope measure the voltage across the capacitor. (You'll need to use the oscilloscope's front-panel controls to get the waveform on the screen and get the triggering to work)
## Are the leading and trailing edges of the pulse similar? Why?
## What is the "rise time" of the leading edge (10% to 90%)?
## What is the "fall time" of the trailing edge (10% to 90%)?
## What is the time it takes for the trailing edge to fall to 1/e of its initial value?
## What is the value of the resistance multiplied by the capacitance?
## Repeat the above measurements with a 1 <math>\mu</math>f capacitor instead of the 10 <math>\mu</math>f capacitor.
## Are the rise and fall times faster or slower?
## What can you say about the rise time as a function of capacitance?
# Next let's use resistors and a capacitors to build one frequency-low-pass circuit and one frequency-high-pass circuit.[[File:LPF.png|right|75px]]
## Use what you've learned about the AC and DC responses of capacitors and resistors to put together a resistor + capacitor network that blocks DC current, strongly attenuates low frequencies but passes high frequencies (hint: recall the voltage divider of 7 above).[[File:HPF.png|right|75px]]
## Determine the circuit's 3dB point.
## Put together a resistor + capacitor network that passes DC current and low frequencies but strongly attenuates high frequencies.
## Determine the circuit's 3dB point. 

==== Inductor Basics ====
[[File:Inductor_symbol.png|thumb|100px|right|Inductor Symbol- L]]
# Measure the inductance of five 1mH inductors. Estimate their tolerance (5%, 10%, 15% or 20%).
## What is inductance? Describe physically a very simple inductor.
## How is energy stored in an inductor?
## What is the inductance of two 1mH inductors in series? How do inductors add in series?
## What is the inductance of two 1mH inductors in parallel? How do inductors add in parallel?
## Do inductors add like resistors or capacitors?
## How does the inductance meter measure inductance? 
# Using a proto-board apply 1VDC '''across''' a 1mH inductor and 500 Ohm resistor in series. Using a MM measure the voltage '''across''' the entire inductor + resistor series network. What is the inductors "resistance" in this situation?
# Put a 1VAC sinusoidal signal across the inductor + resistor network at 50, 500, 2kHz, 5kHz and 10kHz, 25kHz, 50000, 250kHz and 1Mhz.
## At each frequency measure the voltage across the inductor only. Measure the voltage across the resistor only. Explain the measured voltage across the resistor in terms of how the inductor behaves with frequency. 
==== Resonant circuits ====
[[File:LR_Bandpass_filter.jpg|thumb|right|LC resonant circuit - bandpass filter|150px]]
# Construct the circuit shown at the right using a 500 Ohm resistor, 1mH inductor and a 10uf capacitor.
## Apply a 1VAC sinusoidal input voltage at frequencies between 10 and 6200Hz and '''plot''' the output voltage as a function of frequency.
## At what frequency is the response of the circuit maximum?
## Use QUCS or LTSpice to simulate this circuit. These software programs are on the lab desktop computers (or you can put them on your own laptop. You can find information on the programs in these links [http://qucs.sourceforge.net/ QUCS] and [http://www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html LTSpice]. Consult with the instructor or TA concerning how to do this and what the results should look like.
## Explain the response of this circuit based on what you've learned about capacitors and inductors.
## When would a circuit with a response like this be useful?
 

==== Impedance and Reactance ====
Impedance is resistance generalized. A resistor resists (dissipates power) but does not change the waveform (square wave in square wave out). Capacitors and inductors (since they store energy) can react and cause changes in the waveform (see section 8 above).

The concept of impedance includes resistance and reactance effects. That is, '''Impedance = Resistance + Reactance'''. All the frequency dependence is contained within the reactance. For ideal capacitors and inductors their resistance is zero (not the case in real life). An ideal resistor is a purely resistive component and has no reactance (again, not the case in real life).

We can use the word "impedance" in general. When we say something like, "What's the resistor's impedance", we are referring to the resistance term of the resistor's impedance equation. When we say something like, "What's the impedance of the capacitor", we are referring to the reactance term of the capacitor's impedance equation.
# Think back to the previous exercises.
## What is the frequency dependence of a capacitor's impedance?
## What is the frequency dependance of an inductors impedance?

==== Diodes ====
For the electronic components considered above (resistor, capacitor, inductor) it doesn't matter which way you put them into a circuit - they are non-directional. That is, you can flip their leads and the circuit will behave the same. For diodes this is not the case. Diodes are directional and it matters which way they are oriented in a circuit. Diodes are physically more complicated than the components treated above so we won't go into an explanation of just what a diode is now. Here, we'll only consider how diodes behave. For a more detailed study of diodes and transistors you may read Sze's ''Semiconductor Physics'' (on bookshelf): All of chapter 1, sections 2.1, 2.2, 2.3 for basic semiconductor background and sections 3.1, 3.2, 3.3, 3.4 for diodes and PN junctions and section 4.1 for transistor action. 

[[Media:Semiconductor_en.jar |Download and run this PN junction applet]]. By adjusting the bias voltage show that the diode conducts only under forward bias.

[[File:Diodecathan.png|right|Diode]]
# Put a (6V) Zener Diode in series with a MM in ammeter mode and ground the anode.
## Apply 0.7VDC to the cathode and measure the current through the diode.
## Now ground the cathode and apply 0.7VDC to the anode and measure the current through the diode.
## Are the currents the same?
# With the cathode grounded apply voltages from 0-1.5 VDC to the anode in 0.1 V increments and plot the result. This is the forward I-V curve for the diode. The diode is said to be "forward biased" in this situation.
## There should be a "knee" in this curve where the diode "turns on" or conducts. About what voltage is this?
# Using a (current limited) voltage supply, apply voltages from 0-10VDC to the cathode (anode grounded) and plot the result. This is the reverse I-V curve for the diode. The diode is said to be "reverse biased" in this situation.
## There should be a "knee" in this curve too where the diode starts to conduct in the reverse direction. About what voltage is this?
## Are the forward and reverse "turn on" voltages symmetric about 0V?
# Construct the diode clamp circuit shown at the right.[[File:Diode_clamp.jpg|thumb| Diode Clamp|100px]]
## Apply input voltages from 0-10VDC and plot the output voltage vs. input voltage.
## Does the diode clamp earn its name?
## Can you explain the maximum output voltage? 
# Employ an AC voltage divider with a resistor and the P6KE6.8 to measure the diode's capacitance as a function of bias voltage. [[File:Voltage_Divider.png|100px|right]]This diode capacitance issue will play a role later on when we encounter optoelectronic devices. In the AC voltage divider shown at the right the C indicates the capacitance of the diode. That is, don't put a capacitor where "C" is but the P6KE6.8 diode with its cathode grounded. Apply a 20mV AC sinusoidal signal with varying (positive to the anode) DC offsets (larger than 20mV) to the input. The DC offset is the diode's bias voltage. Look for amplitude changes to the AC signal at the output. With the voltage divider formula and the formula for the impedance of a capacitor you should be able to plot the diodes capacitance Cd as a function of bias voltage (the DC offset).
## Does the diode's capacitance decrease of increase with positive bias voltages?
## Is there a limiting behaviour? If so, can you explain it?
## Now measure the diode's capacitance for reverse biases from 0 to 25VDC (positive to the cathode).
## Does the diode's capacitance change much for reverse bias voltages?
 

==== Bridge Circuits ====
This section under construction...

==== Transistors ====

* Read Chpt 2.1, 2.1.1, 2.2.1 and 2.2.3 concerning bipolar transistors in AoE
[[File:Bipolar-junction-transistors.jpg|thumb|right| Transistors|100px]]
All the components (even diodes) examined above are considered "passive" components. That is, they can't supply energy. Transistors are considered "active" in the sense that they can supply energy (or amplify). Like diodes, transistors are physically more complicated than resistors, capacitors and inductors and we won't go into detail about just what they are. Instead we'll focus on how transistors behave. The collector C must be biased more positive than the emitter E. The current through the collector IC is roughly proportional to the current into the base IB (usually anywhere from 50 to 250 times IB). So there you have it. In a first approximation the transistor is a current amplifier. A small current flowing into the base controls a much larger current flowing into the collector.
[[File:Transcurrentamp.png|right|200px]]

# Ground the emitter of a [[Media:TIP31C.pdf |TIP31C]] npn transistor. Put a 22 Ohm resistor in series with a MM in ammeter mode between the collector and a +2.5VDC supply. Put a 1kOhm resistor in series with an ammeter between the base and the +2.5VDC supply. Advice: Make sure you have the transistor pins labeled correctly (maybe look up the spec sheet).
## Measure the collector current and the base current for supply voltages VS between 1.3 to 3VDC.
## Plot IC/IB vs. VS.
## What is the proportionality factor between IC and IB at VS = 1.3VDC?
## Is the proportionality factor independent of VS ?
## Does the transistor amplify current?
# Read Chpt 3.1, 3.1.1, 3.2.1, 3.1.3 concerning Field-Effect Transistors (FETs) in AoE.
 

==== Operational Amplifiers (OpAmps) ====

* Read Chpt 4.1, 4.1.1, 4.1.2, 4.1.3, 4.2.1, 4.2.2, 4.2.3, 4.2.6, 4.2.7, 4.5.7 concerning Operational Amplifiers (OpAmps) in AoE. 
OpAmps are integrated circuits (ICs) that contain within them many transistors, resistors, capacitors and possibly diodes miniaturized into a single IC component (see chapter 9 of the eBook ''Starting Electronics''). [[File:Op-Amp.jpg|thumb|What an OpAmp actually looks like|100px]] OpAmps are very high gain dc-coupled differential amplifiers with single-ended outputs and are usually employed with feedback.
The OpAmp we will be using is National semiconductor's general purpose [[Media:LM741.pdf| LM741]]. OpAmp behaviour can may be simplified into two simple rules.
* The output attempts to do whatever is necessary to make the voltage difference between the inputs zero.
* The inputs draw no (very little anyway) current.

[[File:Opamp.jpg|thumb|right|150px|OpAmp circuit symbol]]
# Use an LM741, a 1kOhm and a 500Ohm resistor to construct the non-inverting amplifier shown at the right (power to OpAmp not shown).[[File:Noninverting.png|thumb|Non-inverting amplifier]]
## Power the OpAmp at +10VDC and -10VDC.
## Apply a +1VDC signal to the input and measure the output voltage.
## Can you explain the OpAmps behaviour in terms of the first rule above?
## What is the gain of your amplifier (Vout/Vin)?
## What is the value of 1 + Rf/Rg?
## Are these last two values the same?
## Replace Rf with Rg and Rg with Rf.
## Apply a +1VDC signal to the input and measure the output voltage.
## What is the gain of your amplifier (Vout/Vin)?
## What is the value of 1 + Rf/Rg (remember you switched the values of Rf and Rg)?
## What is the general formula for the gain of a non-inverting amplifier? 
# Reconfigure the LM741, the 1kOhm and 500Ohm resistors for an inverting amplifier (see diagram at right).[[File:Inverting_Amplifier.png|thumb|Inverting amplifier|200px]]
# Apply a +1VDC input and measure the output.
## Can you explain the OpAmps behaviour in terms of the first rule above?
## What is the gain of your amplifier (Vout/Vin)?
## What is the value of -Rf/Rin
## Are these last two values the same?
## Switch Rf and Rin.
## Apply a -1VDC signal to the input and measure the output voltage.
## What is the gain of your amplifier (Vout/Vin)?
## What is the value of -Rf/Rin (remember you switched the values of Rf and Rin)?
## What is the general formula for the gain of an inverting amplifier?

==== Instrumentation and Loading ====
Since electronic instruments (MMs, oscilloscopes, function generators, even Opamps, etc.) are composed of resistors, capacitors, inductors, diodes, transistors, OpAmps, etc., they have characteristic net input and output impedances.

Consider the simple voltage divider circuit shown at the right.[[File:Voltagedivider.gif|100px|right]]
Let Vin be 10VDC and R1 = R2 = 10MOhm. Based on your experience in section 5 above what do you think Vout should be?
# Construct the voltage divider.
## Let R1 = R2 = 1kOhms. Measure Vout. Is Vout what you expected?
## Change both resistors to 10kOhm. Measure Vout. Is Vout what you expected?
## Change both resistors to 500kOhm. Measure Vout. Is Vout what you expected?
## Change both resistors to 1MOhm. Measure Vout. Is Vout what you expected?
## Change both resistors to 10MOhm. Measure Vout. Is Vout what you expected?
## Plot Vout vs. R2.
## What do you think is going on? Remember how the MM measures voltage.

This voltage sagging effect is the result of circuit loading. The MM bleeds off a small bit of the current and runs it through a very precise calibrated large value resistor (usually between 1MOhm and 10MOhms). When R2 is 1kOhm the MM bleeds off a very small fraction of the current that should have flowed through R2. Consequently, the measured voltage at Vout sags minimally. However, as R2 increases to values approaching the MM's "internal" resistance (or input impedance) the MM draws off larger and larger fractions of the current that should have run through R2. Consequently, the measured voltage at Vout sags substantially.

The voltage divider and MM can be thought of as a two stage electrical device. The first stage does something and then "hands off" the result to the second stage which also does something.

What can you say about the output impedance of a first-stage electronic device in relation to the input impedance of a second-stage electronic device?

==== Unity Gain Non-Inverting Amplifier: The Follower or Buffer ====
The above consideration on instrumentation and loading naturally lead to a very useful OpAmp device. A follower (pictured at right) [[File:Follower.png|thumb|200px| The follower]] is a unity gain non-inverting amplifier. Why would anyone want this? It just reproduces what you've already got.

Well let's consider the follower's input and output impedances. From the second simple rule for OpAmps (see above) the input impedance (looking into the (+) OpAmp input) is "infinite" (well, very high anyway as it draws little to no current). The OpAmp's output impedance (looking from Vout to the (-) OpAmp input) is zero (or very nearly).

So the follower has the useful properties that it's input impedance is "infinite" and it's output impedance is "zero". This would have been a wonderful thing to have between the voltage divider stage and the MM stage in the previous section.

# Redo the measurements of the previous section with the follower (or in this case it's maybe better to call it a buffer) in between the stages.
## Plot the new Vout vs. R2.
## Does Vout still sag with increasing R2? 

==== RF Circuits and PCBs ====

* Read Chapter 1 of ''RF Circuit Design'' by Chris Boswick (on bookshelf in lab).
# Why do discrete-component electronic circuits behave non-ideally at RF frequencies (>= 10MHz).
# What can be done about this?
# Build two discrete-component RLC tank circuit on a protoboard. One at resonant a ("low") frequency (500kHz) and one at a ("high") resonant frequency (30 MHz).
## Plot the Vout vs frequency of the low-frequency tank circuit. Does it behave as expected?
## Plot the Vout vs frequency of the high-frequency tank circuit. Does it behave as expected?
## Explain the two previous results.
# Create and populate a ground-plane PCB of the high-frequency tank circuit above.
## Plot Vout vs. frequency.
## Does it behave as expected? Why?
[[How_To_Make_a_PCB | Read this on PCB construction]]

==== Optoelectronics ====
The electronic components considered above lie completely in the realm of "pure" electronics. In addition to these "pure" electronic components there exists hybrid components that blend the characteristics of electronics and optics. These are called optoelectronic (OE) components and include photodiodes (PDs), light-emitting diodes (LEDs) and laser diodes (LDs). We won't go into detail of what these OE components are but just look at how they behave. Suffice it to say, at this point, that the PD, LED and LD are all diodes and if you understand what a diode is you'll go a long way towards understanding these OE devices.

'''The Photodiode or photodetector:''' Photodiodes are very much like the diodes you encountered above with the exception that currents can be induced not only by biasing voltages but also by light (called the photo-current). Please read about photodiodes in Saleh & Teich's ''Fundamentals of Photonics'' sections 18.1, 18.3 and 18.4 (on bookshelf). [[File:PDsymbol.png|thumb|200px| Photodiode symbol]]
# Measure the "dark" forward I-V curve of Optek's [[Media:OP950.PDF| OP950]] PD (from 0-1.5V). That is, shield the PD from ambient room light while doing the measurement.
## Plot the dark forward I-V curve.
## How does it look compared to the "pure" electronic diode's forward I-V curve?
## At what voltage does the PD "turn on". How does this compare with the "pure" diode's turn-on voltage?
## Now open up the PD to ambient room light and plot at the forward I-V curve again. Has it changed?
## Get a red LD module and shine laser light on the PD. Observe the forward I-V curve again. Has it changed?
## What can you say about the PD's I-V curve as a function of incident light power?
## Measure the dark reverse I-V curve of the PD between 0 and -25VDC.
## Open the PD to ambient light and redo the previous measurement.
## Shine the red laser light on the PD and repeat the measurement again.
## What can you say about the reverse I-V curve of the PD vs. incident light power? 
Please read about light emitting diodes (LEDs) and laser diodes (LDs) in ''Fundamentals of Photonics'' sections 17.1 and 17.3. 

'''The Light Emitting Diode:''' [[File:Led.jpg|thumb|100px| [[File:LED_Symbol.png|thumb|100px| LED symbol]]Typical LED]]The PD above is a device that when light is incident on it a photocurrent is produced. The LED, on the other hand, is a device that when a (suitable) current is induced through it light is produced.
# Forward bias (positive voltages applied to the Anode) ANDOptoelectronic's [[Media:AND114-R.pdf| AND114-R]] LED between 0 and 2VDC.
## What happens as the voltage is increased?
## With a power meter measure the optical power as a function of forward current and plot.
## Are there distinct regimes of optical power output?
## With a spectrometer measure the optical power as a function of wavelength. 

'''The Laser diode:''' Laser diodes are similar to LEDs but in addition have optical feedback. Without going into detail, this [[File:LD.jpg|thumb|Typical LD|right|100px]]feedback greatly improves the optical characteristics of the LD (think of the difference between a flashlight and a laser pointer).

[[Media:Lasers_en.jar | Download and run this laser simulation applet - Try to get the system to lase]]

LEDs are fairly robust devices. You can mistreat them, within reason, and they'll still function (at least to some degree). LDs, on the other hand, are easily destroyed or damaged. 
* Static Electricity: The static electricity generated by walking across a carpet can (and usually does) destroy them.
* Reverse Bias Voltages: LDs (and LEDs too) are meant to operate in forward bias only. As such, they can be destroyed by applying too high a reverse bias to them (this reverse bias damage value is usually spec'd).
* Rapid Current Changes: Abruptly cutting off (or turning on) a LD driving current can (and usually does) destroy the LD.
* Putting too much current through the LD (again, this usually does destroy the LD). 
For all these reasons LD are usually operated within a protective circuit (see right).[[File:CCcircuit.png|thumb|400px|LD Constant Current (CC) Circuit]]

There are two components you haven't seen yet. The [[Media:LM317.pdf|LM317 ]] and the square blue component (the pot) connected to the middle pin of the LM317. A pot or potentiometer is a variable resistor. It's got a knob or screw that can be turned to adjust its resistance.

Let's discuss the parts of this circuit and what they do to help protect and operate the LD. The LM317 is a voltage regulator. The pot allows for adjusting the LD current and the resistors act to limit the maximum current. The "pure" electronic diode clamps any reverse biases (accidentally applied) to ~ 0.6V (which is below the reverse bias damage value). The capacitor suppresses static discharges or voltage transients and slows the LD turn-on/turn-off behaviour.

In addition to the LD protection circuit always wear an [[Media:Antistaticwb.jpg|antistatic wrist band ]] when handling LDs.

Also, it's always best to test your CC circuit with an LED first (LED is more robust - and cheaper) before trying it with the LD. 

The LD we'll use is LiteOn's [[Media:LTLD505T.pdf| LTLD505T]]. It has a center wavelength around 650nm, 5mW optical power, turn-on (or threshold) current around 35mA, operating current 45mA, operating voltage around 2.4V, max operating voltage 2.6V and max reverse voltage of
2V.

# Put together this LD CC circuit with V(-) at ground, V(+) at 7VDC, a 1K pot, , R = 30 Ohms, C = 10<math>\mu</math>f and a P6KE6.8 diode (oriented the correct way).
## Test the CC circuit with an LED (cathode grounded).
## Does the circuit light up the LED? If yes, proceed. If not, troubleshoot the circuit.
## Replace the LED with the LD (remember to wear the antistatic wrist band).
## Does the circuit light up the LD? Is yes, proceed. If not, troubleshoot.
## With the power meter measure the optical power vs. LD current. What's the turn-on current? Is it close to the LD's spec'd threshold current?
## What is the optical power at the operating current?
## Are there distinct optical regimes?
## How does the LD's threshold current relate to these regimes?
## With a spectrometer measure and plot the optical power vs. wavelength for currents just below threshold and well above threshold.
## Are these plots similar? Explain. 
* Submit a write-up outlining your activities, results and the answers to all the questions asked above. 

* '''CLEAN UP THE OBSTACLE COURSE SETUP AFTER USE'''

How to Coat Optical Fibers

2023-03-10T18:10:37Z

Bsboggs: Created page with " ProCoater Read Me"

[[media: ProCoater_READ_ME_-APL.pdf| ProCoater Read Me]]

APL wiki:Community portal

2023-03-10T18:09:42Z

Bsboggs: /* Projects and Modules */

Welcome to the University of Oregon, Department of Physics, Advanced Projects Lab's Wiki.

To see our main website visit [http://june.uoregon.edu Advanced Projects Lab].

== Projects and Modules ==
[[File:APL.jpg|650px|right]]
[[Advanced Projects]]

[[Teaching Modules]]

- ''[[General Lab Equipment Obstacle Course]]''

- ''[[Basic Machining Obstacle Course]]''

- ''[[Optics Obstacle Course]]''

- ''[[Fiber-Optics Obstacle Course]]''

- ''[[Electronics Obstacle Course]]''

- ''[[Digital-Electronics Obstacle Course]]''

- ''[[Make and Test a Semiconductor Device]]''

- ''[[Permittivity and Permeability of Materials Obstacle Course]]''

- ''[[Vacuum Technology Obstacle Course]]''

- ''[[Scientific Python Primer]]''

- ''[[LabVIEW Primer]]''

- ''[[Media:Taking,_Storing,_Transferring_and_Presenting_Data.pdf| Taking, Storing and Presenting Data]]''

- ''[[How to Make a Printed Circuit Board (PCB)]]''

- ''[[How to Test Transistors and FETs]]''

- ''[[Operating Fusion Splicers and Preparing the Fiber]]''

- ''[[How to Coat Optical Fibers]]''

=== Useful Links: ===

[http://www.rp-photonics.com/encyclopedia.html RP Photonics Encyclopedia]

[http://www.newport.com/Tutorials/979935/1033/content.aspx Newport Tutorials]

=== LaTeX Help: ===

[[Working with TeX Equations]]

[http://en.wikipedia.org/wiki/LaTeX LaTeX - Wikipedia]

[[Media:Lshort.pdf |The Not So Short Introduction to LATEX]]

=== Wiki Markup Help: ===

[http://en.wikipedia.org/wiki/Help:Cheatsheet Help:Cheatsheet]

[http://en.wikipedia.org/wiki/Help:Wiki_markup Help:Wiki markup]

[http://en.wikipedia.org/wiki/Wikipedia:Extended_image_syntax Wikipedia:Extended image syntax]

[http://www.mediawiki.org/wiki/Help:Tables Help: Tables]

=== CDF (Computable Document Format) Help: ===
''(Note - The Wolfram CDF player for Linux currently doesn't support the browser plugin)''

[http://www.wolfram.com/cdf-player/ Get the Wolfram CDF Player]

[http://en.wikipedia.org/wiki/Computable_Document_Format CDF - Wikipedia]

[http://www.mediawiki.org/wiki/Extension:WolframCDF#Usage How to include CDF files on wiki pages]

2022-02-17T18:46:37Z

Bsboggs:

File:HeterodyneReceiver.png

2022-02-17T18:06:53Z

Bsboggs:

File:HomodyneReceiver.png

2022-02-17T18:04:00Z

Bsboggs:

RF Communications

2022-02-17T18:01:40Z

Bsboggs: Created page with "== RF communications == Types of Modulation: Amplitude Modulation (AM), Single Side Band (SSB), Frequency Modulation (FM), Phase Modulation (PM) Modulation T..."

== RF communications ==

Types of Modulation: Amplitude Modulation (AM), Single Side Band (SSB), Frequency Modulation (FM),
Phase Modulation (PM) 

Modulation Type: AM 
1.0) Choose frequency/wavelength of interest. 

2.0) Build and test two 1/2 wavelength dipole antennas (send and receive). 
2.1) Input appropriate RF carrier frequency into transmitting antenna (sine wave of ~ 1Vpp). 
2.2) Attach oscilloscope to reveiving antenna and observe transmitted RF carrier wave. 
2.3) Attach RF carrier to LO port of mixer and another sine wave (~ few MHz at 1Vpp) to IF port
of mixer. Attach the mixer's RF port to the transmitting antenna (this is "upconversion"). 
2.4) Observe the modulated RF carrier with an oscilloscope attached to the receiving antenna. 
2.5) Is the carrier frequency clearly present (use o-scope's FFT function to observe)?
Are the side bands clearly present and at the correct frequency offsets? Vary the
modulation frequency of the sine wave sent to the mixer's IF port. Do the RF
sidebands follow suite? 

Types of receivers: Homodyne (or Direct Conversion), Heterodyne, Superheterodyne 
If the LO input to the receive-side mixer is of the same frequency as the LO on the send side
you have a homodyne or direct-conversion receiver (if not, you have a heterodyne receiver).
If the IF on the receive side is above audible frequencies an additional mixer is
required to bring the IF down to audible frequencies (this is known as a superheterodyne
receiver - the "super" refers to "super audible"). 

3.0) Use two mixers and suitable fxn generators and filters to mod/demod audio frequency (AF ~ a few kHz) on an RF carrier.
Use one mixer on the receiving side to build a homodyne receiver (this is called "downconversion"). 
3.1) Observe AF on the o-scope. 
3.2) Send and receive various audio tones (use a speaker and amplifier on the receive side to
hear the AF tones). 
3.3) Attach microphone and amplifier to IF port of transmitting system. 
3.4) Send and receive voice. 
3.5) Build a heterodyne receiver. 
3.6) Build a superheterodyne receiver. Repeat steps 3.1-3.4 

4.0) Using the superheterodyne receiver, build an RF pre-selection bandpass (BP) filter between the antenna and the mixer on the receive side
(centered on the RF carrier with appropriate bandwidth). 
4.1) Build preamp between the pre-selection filter and the receive mixer (gain ~ 100). 
4.2) Build an IF filter then a low noise amplifier (LNA) between the first mixer's IF port and the second mixer. 
4.3) Build an AF filter and power amp between the second mixer and the speaker.
(choose bandwidth wisely ~ 300-3kHz) 
* FM mod/demod - Build transmit/receive circuits
* Direct Conversion I/Q Software Defined Radio (SDR) - DAQ/Labview interface

** Digital modes???* FM mod/demod - Build transmit/receive circuits 

Equipment: wire for antennas, wood for support, BNC connectors, solder, mixers (at least double balanced), fxn gens
and filters, speaker, amplifier

Advanced Projects

2022-02-16T22:46:39Z

Bsboggs:

== Optics Projects ==

* [[Spontaneous Parametric Downconversion]]

* [[Sonoluminescence]]

* [[Optical Tweezers]]

* [[Optical Tweezers for Biology]]

* [[External-Cavity Tuneable Diode Laser]]

* [[Optics Modeling with Optica]]

* [[Schlieren Flow Visualization]]

* [[Laser-Matter Interaction Studies]]

== Fiber-Optic Projects ==
* [[Modelocked Fiberlaser]]

* [[Sagnac Fiber-Optic Gyroscope]]

* [[Erbium-Doped Fiber Amplifier & CW Laser]]

* [[Mode-locked Erbium-Ytterbium Doped Fiber Laser]]

* [[Master Oscillator Power Amplifier Pulsed Laser]] (not currently offered)

* [[Graphene as Saturable Absorber]]

* [[Fiber Simulations with RP Fiber Power]]

*[[Optical Chaos with External Feedback Mirror]] (not currently offered)

== Solid State Projects ==

* [[Atomic Force Microscope]] (not currently offered)

* [[OAM & Surface Plasmon Resonance]]

* [[Superconductivity]]

* [[MgB2 Superconductor]]

* [[Physics of Semiconductor Devices]]

* [[Physical Adsorption]] (not currently offered)

* [[Nuclear Magnetic Resonance]]

==Thermodynamics==

* [[Heat Content Asymptotics]] (not currently offered)

== Computational Projects ==

* [[MEEP]]

* [[Parallel Programming on the APL Cluster]] (not currently offered)

* [[Data Mining]]

* [[Robotics]]

* [[APL HPC Cluster]]

== Astronomical Projects ==

* [[Observational Astronomy]] (offered Spring Term)

* [[Astronomical Spectroscopy]]

==RF Communications==

* [[RF Communications]]

== Useful Info==

[[Media:How_To_Make_A_Cable.pdf | How To Make a Multi-Strand Shielded Cable]]

[[Media:How_To_Connectorize_BNC_Cables.pdf | How To Make a BNC Cable]]

2019-05-29T18:12:28Z

Bsboggs: