Week 6

Week 6 Blog

Operational Amplifiers

1. You will use the OPAMP in “open-loop” configuration in this part, where input signals will be applied directly to the pins 2 and 3.

Figure 1: Image of IC chip, and schematics of (Non)-Inverting Amplifiers

~~a. Apply 0 V to the inverting input. Sweep the non-inverting input (Vin) from -5 V to 5 V with 1 V steps. Take more steps around 0 V (both positive and negative). Create a table for Vin and Vout. Plot the data (Vout vs Vin). Discuss your results. What would be the ideal plot?

Figure 1a) An OP-AMP cannot exceed the supply voltage, in this case +5 V and -5 V. This is illustrated by the orange line. However, since ideal measurements are only theoretical, our measured values only were at -3.6 and +4.5 V. The other main difference between our measured and ideal values is that, because the gain is so high, the graph looks like a vertical line at 0. At 0, our DMM read -3.6 V.

~~b. Apply 0 V to the non-inverting input. Sweep the inverting input (Vin) from -5 V to 5 V with 1 V steps. Take more steps around 0 V (both positive and negative). Create a table for Vin and Vout. Plot the data (Vout vs Vin). Discuss your results. What would be the ideal plot? 

Figure 1b) As you can see, this graph is essentially the reverse of Figure 1a. This makes sense because the circuit was mostly the same, except for the fact that our input voltage was connected to the inverting input. The same still holds true for the limits of the output voltage. However, at 0 our DMM read 4.54 V. The fact that no OP-AMP is ideal is why the orange and blue lines are not the same.

2. Create a non-inverting amplifier. (R2 = 2 kΩ, R1 = 1 kΩ). Sweep Vin from -5 V to 5 V with 1 V steps. Create a table for Vin and Vout. Plot the measured and calculated data together. 

Figure 1c) Our calculated values show what an ideal non inverting OP-AMP graph would look like. As you can see the values we measured were higher/lower than ideal, which is what one would expect. The gain for this circuit was 3. 

3. Create an inverting amplifier. (Rf = 2 kΩ, Rin = 1 kΩ). Sweep Vin from -5 V to 5 V with 1 V steps. Create a table for Vin and Vout. Plot the measured and calculated data together.

Figure 1d) Our calculated values show what an ideal inverting amp graph would look like. As you can see the values we measured were lower/higher than ideal, which is what one would expect. The gain for this circuit was -2. As the name indicates, an inverting amplifier takes a negative input voltage and outputs a positive voltage, and vice versa.

4. Explain how an OPAMP works. How come is the gain of the OPAMP in the open loop configuration too high but inverting/non-inverting amplifier configurations provide such a small gain? 
~~The OPAMP works by using two inputs (+ and -) to receive electricity. If more voltage goes through into the + than the - then it outputs as much voltage as it can. Visa Versa, if more voltage enters into the - than the + then it outputs no voltage.
~~The OPAMP in the open loop has a gain much higher than the inverting/non-inverting configuration. If we simply look at the equations we see

Open loop gain: ( Vout )/( V+ - V-  )

Inverting gain: -(Rf / Rin)

Non-inverting gain:1+ (R2 / R1)

***REFER TO FIGURE 1 FOR DETAILS PERTAINING TO THE RESISTORS***

~~Generally the reason why the gain is smaller is because the resistors dampen the abilities to produce higher gain.

Temperature Controlled LED System

1. Connect your DC power supply to pin 2 and ground pin 5. Set your power supply to 0V. Switch your multimeter to measure the resistance mode; use your multimeter to measure the resistance between pin 4 and pin 1. Do the same measurement between pin 3 and pin 1. Explain your findings (EXPLAIN).

Vin	Pins 1 to 3	Pins 1 to 4
0 V	0.953	OL
1 V	0.949	OL
2 V	0.961	OL
3 V	0.959	OL
4 V	0.976	OL
5 V	0.996	OL
6 V	OL	0.960
7 V	OL	0.962
8 V	OL	0.963

2. Now sweep your DC power supply from 0V to 8V and back to 0V. What do you observe at the multimeter (resistance measurements similar to #1)? Did you hear a clicking sound? How many times? What is the “threshold voltage values” that cause the “switching?” (EXPLAIN with a VIDEO).

Video explaining how the relay clicks during energizing and de-energizing phases

*Further explaination: For pins 1 to 3 and pins 1 to 4 the multimeter was reading the same as number 1. I heard 4 clicks when I did the operation for both trials. The clicks closer to the 0V was a deeper click and the clicks closer to the 8V had a higher toned pitch. The Threshold voltage is about 6 voltages when it energizes and then about 2 V is the lower side when it de energized.

3. How does the relay work? Apply a separate DC voltage of 5 V to pin 1. Check the voltage value of pin 3 and pin 4 (each with respect to ground) while switching the relay (EXPLAIN with a VIDEO).

Video explaining how a relay works as a switch and an amplifier 

Pin 3	Pin 4
1.2 ohms	1.1 ohms
OL	OL

 *These are the numbers we got when running this experiment

LED + Relay 

1. Connect positive end of the LED diode to the pin 3 of the relay and negative end to a 100 ohm resistor. Ground the other end of the resistor. Negative end of the diode will be the shorter wire.

2. Apply 3 V to pin 1

3. Turn LED on/off by switching the relay. Explain your results in the video. Draw the circuit schematic (VIDEO)

Video showing how the relay is amplifying the signal to power the LED

This is the schematic of our LED+Relay Circuit.

Operational Amplifier

 1. Connect the power supplies to the op-amp (+10V and 0V). Show the operation of LM 124 operational amplifier in DC mode with a non-inverting amplifier configuration. Choose any opamp in the IC. Method: Use several R1 and R2 configurations and change your input voltage (voltages between 0 and 10V) and record your output voltage. (EXPLAIN with a TABLE)

Input	Output (R1= 100 ohm, R2=100 ohm)	Output (R1= 1000 ohm, R2=100 ohm)	Output (R1= 1200 ohm, R2=100 ohm)
1	1.3	1.8	2.1
5	4.91	6.33	6.8
7	7.6	7.7	7.9

    *Table displaying our results from the op-amp experiment     

2. Use your temperature sensor as your input. Do you think you can generate enough voltage to trigger the relay? (EXPLAIN)

*CAN'T DO NO TEMPERATURE SENSOR TO USE.

But if we had to hypothesize then no I don't believe our temperature sensor alone can trigger our relay, because it won't have enough voltage to it.

3. Design a system where LED light turns on when you heat up the temperature sensor. (CIRCUIT schematic and explanation in a VIDEO)

*CAN'T DO NO TEMPERATURE SENSOR TO USE.

But if we had to only draw the circuit out this is what we would get started with below:

*Note we didn't include the voltages or the resistance, because without trying the circuit we don't actually know the real numbers to it. So we just labeled everything ambiguously (V1,V2 and R1).