Week 6

Blogsheet week 6

Operational Amplifiers

Explanations of the pin numbers are below:

1: DO NOT USE	8: DO NOT USE
2: Negative input	7: +10V
3: Positive input	6: output
4: -10 V	5: DO NOT USE

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.

a.       Apply 0 V to the inverting input. Sweep the non-inverting input (V_in) from -10 V to 10 V with 1 V steps. Take more steps around 0 V (both positive and negative). Create a table for V_in and V_out. Plot the data (V_out vs Vi_n). Discuss your results. What would be the ideal plot?



      Table 1                                                   Graph 1: Inverting graph in open loop

Vin (V)	Vout (V)
-5	4.68
-4	4.68
-3	4.68
-2	4.68
-1	4.68
-0.5	4.68
0	0
0.5	-3.77
1	-3.77
2	-3.77
3	-3.77
4	-3.77
5	-3.77

In our graph, the slope of the plot should be close to 0. As shown above, the slope of our graph should've been closer to 0, but the outcome of what we have shown in the graph may be from the lack of more data between 0 and +/- 1 V. However, Vout flattens out at 4.68 V at -5V and -3.77 V at 5 V. This occurs because the output can only go so high/low, thus flattening out at the maximum/minimum values. This may also be because of the type of equipment we use. Since it is an inverting input, our output should be the opposite of our input, which our chart clearly shows.

b.      Apply 0 V to the non-inverting input. Sweep the inverting input (V_in) from -10 V to 10 V with 1 V steps. Take more steps around 0 V (both positive and negative). Create a table for V_in and V_out. Plot the data (V_out vs Vi_n). Discuss your results. What would be the ideal plot?

Table 2:                                                  Graph 2: Non-inverting graph in open loop

Vin (V)	Vout (V)
-5	-3.77
-4	-3.77
-3	-3.77
-2	-3.77
-1	-3.77
-0.5	-3.77
0	0
0.5	4.68
1	4.68
2	4.68
3	4.68
4	4.68
5	4.68

Our plot should be similar to the plot above, however the output will be positive and negative respective to the input because the input is non-inverting. The slope should've been closer to 0 also. As shown in our table, when Vin is negative, Vout will also be negative, and same for when Vin is positive.

2.       Create a non-inverting amplifier. (R₂ = 2 kΩ, R₁ = 1 kΩ). Sweep V_in from -10 V to 10 V with 1 V steps. Create a table for V_in and V_out. Plot the measured and calculated data together.



Table 3:                                                  Graph 3:Non-inverting with resistor values

Vin (V)	Vout (V)
-5	-3.77
-4	-3.77
-3	-3.77
-2	-3.77
-1	-3.77
-0.5	-3.77
0	0
0.5	4.68
1	4.68
2	4.68
3	4.68
4	4.68
5	4.68

In our table,  Vout are positive and negative respectively since it's non-inverting. When Vin is negative, Vout will also be negative; when Vin is positive, Vout is positive.

3.       Create an inverting amplifier. (R_f = 2 kΩ, R_in = 1 kΩ). Sweep V_in from -10 V to 10 V with 1 V steps. Create a table for V_in and V_out. Plot the measured and calculated data together.

Table 4:                                                   Graph 4: Inverting with resistor values

Vin (V)	Vout (V)
-5	4.13
-4	4.13
-3	4.13
-2	4.13
-1	2.91
-0.5	-1.5
0	0.8 mV
0.5	-2.91
1	-3.5
2	-3.5
3	-3.5
4	-3.5
5	-3.5

When Vin is negative, Vout is positive; when Vin is positive, Vout is negative. This is because it's inverting. 

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?

      An OPAMP works by amplifying the input voltage, but it can’t exceed the +/- 5 voltage source. It levels out at a certain point. The resistors affects the gain in the inverting/non-inverting amplifier while in the open loop, it doesn’t affect the gain. Since open loop is infinite, the gain will be much higher.

5.

Temperature Sensor: Put TMP36 temp sensor on breadboard.

·         Connect the +V_S to 5 volts and GND to ground.

·         Using a voltage meter, measure the output voltage from the V_OUT. Now put your finger (or cover the sensor with your palm) on the TMP36 temperature sensor for a while, observing how the output voltage changes. Check Fig. 6 in the data sheet (EXPLAIN).

6.   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). 

• The resistance between pin 4 and pin 1 is 0.35 Ω, so basically 0 Ω because voltage is set at 0 V and pin1 and 4 are normally closed.
• The resistance between pin 3 and pin 1 is infinite, because pin 1 and 3 are normally open.

7.   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 1: Sweeping DC power supply to cause clicking sound

8.  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 2: Explanation of relay with basic drawings 

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 3: Explanation of turning the LED on/off with relay

Operational Amplifier (data sheet under Bb/week 6)

1.       Connect the power supplies to the op-amp (+10V and -10V). 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 and record your output voltage. (EXPLAIN with a TABLE)

R1:  1.2 kΩ  R2: 2 kΩ

Vin	0 V	2 V	5 V	7 V	8 V	10V
Vout	79  mV	5.7 V	9.1 V	9.1 V	9.1 V	9.1 V

R1: 47 Ω   R2: 357 Ω

Vin	0 V	2 V	5 V	7 V	8 V	10 V
Vout	0 V	8.5 V	8.5 V	8.5 V	8.5 V	8.5 V

       When using the same Vin values, our Vout values are different when using different resistor values.
 

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

Yes, you can generate enough voltage to trigger the relay. The heat applied to the temperature sensor increases the output voltage, causing the relay to trigger. Without heat, the voltage at first is low, starting around 1.6 V, but when we applied heat from the hair dryer, the voltage began to increase drastically. 

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

Video 4: Schematic of the system and explanation

1.       BONUS! Show the operation of the entire circuit. (VIDEO)

Video 5: Run through of our circuit