Wednesday, January 25, 2017

Blog 3 Group 1

1. Compare the calculated and measured equivalent resistance values between the nodes A and B for three circuit configurations given below. Choose your own resistors. (Table)

R1= 99.6 Ω
R2= 47.2 Ω
R3= 99.6 Ω
R4= 120.5 Ω

A: Measured: 24.9 Ω
     Calculated: 99.6 Ω // 47.2 Ω //99.6 Ω = 32.024//99.6 = 24.2326

B: Measured: 131.0Ω
     Calculated: 99.6Ω + (47.2Ω // 99.6Ω) = 99.6 +32.024 = 131.624

C: Measured: 137.7Ω
     Calculated: 99.6Ω + 47.2Ω //(99.6Ω +120.5Ω)
                        99.6Ω + 47.2Ω//220.1Ω
                        99.6Ω + 38.8654Ω                
Group Measured Rab 
Calculated Rab
A 24.9Ω 24.2326Ω
B 131Ω 131.624Ω
C 137.7Ω 138.465Ω

2.Apply 5V on a 120 Ω resistor. Measure the current by putting the multi-meter in series and parallel. Why are they different?
Parallel: 63.1 mA
Series: 41.8 mA
When measuring in parallel you are basically providing an alternate path of current through the power supply which happens to be less than the equivalent resistance of the circuit. Therefore, the new equivalent resistance of the power supply in parallel with the circuit decreases. Given V=IR if the resistance decreases the voltage is held constant then the current must increase to compensate.

3. Apply 5 V to two resistors (47 Ω and 120 Ω) that are in series. Compare the measured and calculated values of voltage and current values on each resistor.
Calculated Values: V=IR
5V/(120.5+47.2Ω)=29.8 mA
29.8 mA*120.5Ω= 3.59 Volts
29.8 mA*47.2Ω=1.407 Volts
Measured Values:
120.5 Ω=3.59 Volts
47.2 Ω=1.39 Volts
Measured Current:
28.85 mA

4. Apply 5 V to two resistors (47 Ω and 120 Ω) that are in parallel. Compare the measured and calculated values of voltage and current values on each resistor.
Measured Values:
V120.5=4.97 Volts
V47.2=4.97 Volts
Measured Current:
I120.5=39.41 mA
I47.2=94.6 mA
Calculated Values: V=IR
4.97V/(120.5//47.2)=4.97V/33.91Ω=146.5 mA
I120.5=41.21 mA
I47.2= 105.2 mA
Our values calculated values were relatively close to our measured values. However, there seems to be some significant error in our measurements possibly by using a 4W measurement we could have more accurately measured our resistances.

5. Compare the calculated and measured values of the following current and voltage for the circuit below: (breadboard photo) a. Current on 2 kΩ resistor, b. Voltage across both 1.2 kΩ resistors. 
a. Current on the 2kΩ resistor:
Calculated: V=I*Req
I=2.20 mA

b. Voltage across both 1.2kΩ resistors:
R2:=>1.984 mA (0.5197 kΩ /0.75454) = 1.383 mA
R2= 1.032 V -1.383 mA(0.1 kΩ) = 0.8133 Volts
V1=.926 Volts
V2=.785 Volts

Figure 1: Shows the breadboard circuit used.

6. What would be the equivalent resistance value of the circuit above (between the power supply nodes)?
The equivalent resistance across the circuit is 2,519.7Ω.

7. Measure the equivalent resistance with and without the 5 V power supply. Are they different? Why? 
Without the 5V connected, you get a value of 2.463kΩ.  When the power supply is attached you receive a value of 1.89kΩ.  The reason you get a difference in values is because the power supply acts like another resistor in parallel with the entire circuit which happens to be less than the resistance of the entire circuit. This brings down the resistance being read by the DMM.

8. Explain the operation of a potentiometer by measuring the resistance values between the terminals (there are 3 terminals so there would be 3 combinations). (video)

Video 1: Shows the different resistance readings of the different pins of the potentiometer.

Between the left and middle pins on the potentiometer, there was very minimal resistance reading. Then both, the left and middle pins, when put with the right pin came back with a resistance of 10kΩ. It works as a voltage divider.

 9. What would be the minimum and maximum voltage that can be obtained at V1 by changing the knob position of the 5 KΩ pot? Explain.
Max voltage: 5V
Min voltage: 0V
By changing the position of the knob you are adjusting the amount of resistance that the potentiometer is outputting.  So the max amount of voltage is what is put into it, and if the resistance is turned all the way up then the voltage is being dissipated across the other two pins.

10. How are V1 and V2 (voltages are defined with respect to ground) related and how do they change with the position of the knob of the pot? (video)
V1: 5.0 volts.  There is no voltage drop since there is nothing to cause any power loss.
V2: 4.19 Volts

Video 2: Shows the potentiometer changing the voltage on the circuit.
The voltage does not change till with the potentiometer until after the resistor.

11. For the circuit below, YOU SHOULD NOT turn down the potentiometer all the way down to reach 0 Ω. Why?
You should not turn it all the way down because the current will become too high through the other branch and burn up the potentiometer.

12. For the circuit above, how are current values of 1 kΩ resistor and 5 KΩ pot related and how do they change with the position of the knob of the pot? (video).
Through the 1kΩ Resistor we receive a current value of 4.96 mA.  The pot doesn't change the current since it is in parallel.  The 5kΩ pot received a current of .99 mA.

Video 3: The video shows how the pot changes the current values based on how you turn it.

13. Explain what a voltage divider is and how it works based on your experiments.
When two resistors are in series, they divide and change the voltage across the circuit.  With a potentiometer, you can change their resistance, which then would change the voltage drop across each resistor causing a different division of the voltage.

14. Explain what a current divider is and how it works based on your experiments.
A current divider is very similar to a voltage divider.   The difference between the two is that the resistors are in parallel instead of series.  The voltage would be the same, but they would have different currents leaving each resistor.  With the potentiometer, you can adjust the circuit based on current instead of voltage now.

Wednesday, January 18, 2017

Blog 2 Group 1

Scout Case and Austin Kane

1.  What is the role of A/B switch?  If you are on A, would B still give you a Voltage?
The role of the A/B switch is it allows you to switch between two different adjustable voltages between 0-24 Volts.  If A is on, B will still be giving a voltage however the reading on the power supply will only read the voltage supplied to A.  If it is in Tracking mode it it can be linked in parallel or series with A which essentially means A and B are connected.

2. In each channel, there is a current specification (either 0.5 A or 4 A). What does that mean?
For each channel that is the max current allowed before it overloads the circuit.  .5 A is with the A and B switch because it can go up to 24 V.  The 4 A is for the fixed 5 V channel.

3. Your power supply has two main operation modes for A and B channels; independent and tracking. How do those operation work? (Video) 
Video 1: Shows the difference between tracking and independent mode.

The operations work like this.  In independent mode the voltages are free of each other. In tracking mode the voltages are linked together, allowing to get higher voltages we normally wouldn't be able to obtain.  In series tracking mode you can achieve up to 48 V and a current of .5 A.  In parallel you can achieve up to 24 V but a current of 1 A.

4. Can you generate +30 V using a combination of the power supply outputs? How? (Photo)

Fig 1: Shows a reading of +30 volts on the DMM
Fig 2: Shows the setup for the +30 volts reading.

Yes, you can achieve this by putting the power supply on series mode allowing the two voltages to link together.

5. Can you generate -30 V using a combination of the power supply outputs? How? (Photo)
Fig 3: Shows a reading of -30 Volts.
Fig 4: Shows the setup for the -30 Volts.

Yes, you can achieve this by just switching the ground and positive terminals which would make it read from the negative side.

6. Can you generate +10 V and -10 V at the same time using a combination of the power supply outputs? How? (Photo)
Fig 5: Shows a reading of -10 Volts.
Fig 6: Shows the reading of +10 Volts.

Yes, you put them in series mode.  You change the positive lead of the multi-meter to read from the negative terminal and then to the positive terminal.

7. Apply 5V to a 100 Ω resistor and measure the current by using the DMM. Compare the reading with the current meter reading on the power supply. At what angle of the current knob makes the LED light on? If you keep on decreasing the current limit, what happens to the voltage and current? (Video)
Video 2: Shows a video of how the current controls the circuit.

The light will come on if the angle of the knob gets below what is required to run the circuit. The video will show the angle.  If you keep decreasing the knob below the required current limit, both the voltage and the current will begin to drop until there is no voltage and current left. In addition, the LED will come on indicating that the current is being fixed as opposed to the voltage.

8. Where is the fuse for the power supply? What is it for?
The fuses are located in the front by the fixed and A channel.  There is also a fuse located in the back underneath the cord, which is the fuse for the power coming in.  The fuse is used to limit the current coming through the power supply.  If the current gets to high then the fuse will blow to cause a break in the circuit so that there is no current running through it. This safety feature helps protect the more expensive components of the power supply.

9. Where is the fuse for the DMM? What is it for?
The fuse for the DMM is located in the bottom right corner of the front panel.  There is also a fuse located in the back of the DMM by the plug.  Once again, in order to protect the more expensive components of the equipment if to much current goes in (2 amps is the max) it will trip the fuse not allowing current to flow.  There is also another location on the DMM that you can use up to 15A max, which doesnt use the same fuse as the 2A max fuse.

10. What is the difference between 2W and 4W resistor measurements?
The difference between a 2 wire and 4 wire resistor is that the 4 wire is for lower resistances because it reduces the effect of test lead resistance.  2 wire can handle up to 100 ohms of resistance.  For the 4 wire resistance, it can handle up to 1000 ohms.  So the difference between the two would be how much resistance each can handle.

11. How would you measure current that is around 10 A using DMM?
Instead of using the normal setup for current, which uses the 2 A fuse, you would use the 12 A setup which has a max of 15 A. The ground would stay the same, just the positive lead location changes.

Friday, January 13, 2017

Blog 1 Group 1

Scout Case and Austin Kane

1.  What is the class format?
Monday: Quiz discussion for 15 minutes, then lab intro, then lab for the rest of class.
Wednesday: Finish up the lab.
Friday: Comment and discuss the blogs.
Nonclass days: Work on blogs and comment on others.
-The class is out of 1000 total points which are received through; Quizzes, blog reports, blog discussion, final project, midterm exams, and final exams.

2.  Important safety rules:
-Know where fire extinguisher, first aid kit, telephone, and emergency numbers are located.
-Check equipment to make sure it isn't defective.
-Keep things clean.
-When not using equipment turn it off.
-Make sure equipment with electricity is grounded.
-Keep hands dry.

3.  Does current kill?
Yes, if the current is between .1 and .2 mA it will kill you. If it is just above or below it can cause horrific pain, lungs to shut down, and also burns.

4. How to read color coding on a resistor:

5.  The tolerance is the percentage of error in the resistor's resistance. An example in the experiment that we conducted was that each resistor contained a band on the end that was either gold or silver.  Gold was a 5% tolerance, and silver is a 10% tolerance.

6.  Prove all the resistors are within the tolerance range:
Color Band Resistance(Ω)  Tested Resistance (Ω) Tolerance Range (±5%) 
2.2 (kΩ) 2.174  (kΩ) 2.09-2.31  (kΩ)
390 388 370.5-409.5
175 175.8 166.25-183.75
272 270.8 258.4-285.6
150 148 142.5-157.5
151 150.1 143.45-158.55
270 269.5 256.5-283.5
202 202.2 191.9-212.1
201 200.9 190.95-211.05
681 680 646.95-715.05
The values obtained from doing the tests all fall within the tolerance range of 5%.
The range is the max and min that the tolerance would allow.

7.  What is the difference between measuring the voltage and current using a DMM? why?
When you are measuring voltage, you have to have the DMM in parallel with the circuit.  When you are measuring current you have to have the DMM in series with the component you want to measure the current through. This requires you to break the circuit for measuring current.

8.  How many different voltage values can you get from the power supply? Can each one of them be changed to any value?
There are 3 different voltage values you can obtain from the power supply.  Two of them you can change from 0-25 volts and the third value is a fixed value of 5 Volts.

9.  Practice Circuit Results:
Voltage Drop: 5.36 V
Current through the Resistor: 61.2 mA
Resistance: V=I*R so 5.36 V =  .0612 A * R, R=87.58 Ω

Doing the process of working the circuit to test for the current and the voltage.

The Circuit board used to test the resistor.

10. How do you experimentally prove Ohm’s Law? Provide measurement results. Compare calculated and measured voltage, current, and resistance values. 
You experimentally prove Ohms law by recording the voltage and current at different levels of each, once you do those you can solve for the resistance.  The values obtained should come back very close to the actually given resistance. 

Trial 1: 83 Ohm Resistor
Volts (V) Current (A) Resistance (Ω)
5 0.0612 87
7.95 0.0912 87
10.3 0.1206 85.406
12.75 0.152 83.88
15.2 0.189 84.2
Trial 2: 53 Ohm Resistor:
Volts (V) Current (A) Resistance (Ω)
1.11 0.026 42.69
2.209 0.0412 53.616
3.5 0.0656 53.35
4.3 0.0804 53.482
5.34 0.1002 53.29

Testing Results for Circuits and Currents:

11. Rube Goldberg Circuit:

12. Circuit diagram for the Rube Goldberg setup:

13. We could have an L.E.D. that is triggered causing the photo resistor to activate which would spin the motor causing it to wind up string moving a bar which was blocking a ball which could then go trigger another Rube Goldberg set up

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