Exercise 1 - Øving 1 PDF

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TPK4125 - Mechatronics

Exercise 1. Ohm’s law This exercise will introduce you to Multisim Live (an online tool) and NI Elvis III (a platform to create circuits). These are tools that will be used throughout the course to simulate and implement the theory you learn. The tasks that only require calculations and/or multisim are possible to do anywhere. The tasks that require NI Elvis III must be performed at the lab.

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To be able to save your simulated circuits, you need to create an account on https://www.multisim.com

You will start this lab by analyzing a circuit that demonstrates Ohm’s Law. First, you will use Ohm's Law to calculate the current flowing through a resistor for resistances of 330 Ω, 1 kΩ, and 3.3 kΩ. Then, you will calculate the current given different supply voltage values, as shown in the table below. Finally, you will find these values using a simulated circuit and compare your observed values to those you have calculated.

Task 1) Enter the calculated values in the table.

Supply Voltage (V)

R=330 Ω

R=1 kΩ

R=3.3k Ω

Calculated I (mA)

Calculated I (mA)

Calculated I (mA)

1 2

Simulate: Ohm’s Law Measurement You will use Multisim Live to simulate a circuit with a 330 Ω resistor and varying voltages, from 1 V to 5 V, and record the current in each case. Then, you will repeat the process with 1 kΩ and 3.3 kΩ resistors. Instructions:

Simulate Your First Circuit 1. Access the Multisim Live circuit Ohm’s Law at: https://www.multisim.com/content/sZ2Da8WmAn6mXq23mHC9NP/o hms-law/. Notice that the circuit uses a DC power supply to provide voltage across a resistor. 2. Click on and modify the V1 power supply voltage to 1 V. 3. Click Run to begin simulating the circuit. 4. Measure the current detected by the DC current probe PR1.  

Open Split view to see the charted value of the current. If necessary, adjust the scale of the graphing window to see the value of the current.

Task 2) Record the measured current in the appropriate location in the table.

Supply Voltage (V)

R=330 Ω

R=1 kΩ

R=3.3k Ω

Measured I (mA)

Measured I (mA)

Measured I (mA)

1 2

Simulate Varying Voltages 1. Modify the voltage at V1 to 2 V, according to the table above. 2. measure the DC Current. 3. Record your results in the table. 4. When all of the measurements for the 330 Ω resistor have been taken, stop the simulation by clicking Stop. Simulate a 1 kΩ Resistance 1. When the simulation is stopped, double-click the 330 Ω resistor and change the resistance to 1000 Ω, or 1 kΩ. 2. Click Run to begin simulating the circuit. 3. Modify the voltage provided by V1 to values of 1 V through 2 V, as directed in the table above. 4. Measure the DC current using the Current Probe, and record your results in the table. 5. When all of the measurements for the 1 kΩ resistor have been taken, stop the simulation by clicking Stop.

Simulate a 3.3 kΩ Resistance 1. When the simulation is stopped, double-click the 1 kΩ resistor and change the resistance to 3300 Ω, or 3.3 kΩ. 2. Click Run to begin simulating the circuit. 3. Complete the last column of the table by modifying the voltage at V1 and recording the current. 4. Click Stop when you have completed the table. Task 3) Implement: Finding Resistance of an Unknown Resistor

You will use the NI ELVIS III to experiment with Ohm's law and confirm the value of a resistor compared to its color code specification. In this activity, you will randomly select a resistor and wire it into a circuit using the NI ELVIS III. By applying a known voltage and measuring the current, you can calculate the unknown value of the resistor. To be able to use the digital multimeter (DMM), connect NI ELVIS III to your computer and go to https://measurementslive.ni.com/. When turning your NI Elvis III on, wait until you see writing appear on the display, after this you can click “Connect” under “Manage device connection” on https://measurementslive.ni.com/. (Note: the display on NI Elvis III may go blank after a few seconds, that is normal).

Instructions: 1. Make sure that the protoboard is switched off while wiring by pressing the black button in top left corner of your NI Elvis III with the writing “Application board power” so that the blue light on the button is off. This applies for every time you change your circuit.

2. Select a random resistor from the kit and connect it into the following circuit:

Figure 1-5 Circuit diagram for measuring the current through the random resistor. 2. The digital multimeter (DMM) is accessed by clicking on “Click here to add instruments” and choosing Digital multimeter. 3. Turn on your protoboard 4. Choose DC current on the DMM and press “Run”. Measure the current through the circuit using the DMM. 5. Use Ohm's Law to calculate the resistance of the resistor, knowing that 5 V is applied. a) What is the measured current? b) What is the calculated resistance? Confirm Resistance Using Color Codes and DMM:

Resistors are color-coded to indicate their values. Check the specified resistance of the one you selected using the color code: https://en.wikipedia.org/wiki/Electronic_color_code#Resistor_colorcoding.

c) According to the color codes, what resistance should the resistor demonstrate?

Now, use the digital multimeter to directly measure the resistance of the component. 1. Change the circuit configuration to the following:

Figure 1-6 Circuit diagram for measuring the resistance of the component with the DMM.

2. Measure the resistance of the component using the DMM set to resistance mode. 

If the reading is over, increase the Range.



Make sure to turn off the protoboard while measuring resistance

d) What was the measured resistance value of the component? e) Do the calculated and measured resistance values fall within the color code range? Why or why not?

Kirchoff’s voltage law (KVL) Task 4) Calculate Using KVL

You will soon simulate a circuit that demonstrates KVL. Before you begin the simulation, you will use KVL to calculate voltage and current values against which you may compare to your measurements later on. For the circuit shown, calculate the total current and the voltage drop value at each of the resistors, given a power supply of 6 and 12 Volts. To calculate the voltage drop, use KVL, in combination with Ohm's law.

Figure: Calculate the voltage drops in this circuit

a) Complete these calculations: Vs (V)

Calc – Total Current (mA)

Calc – R1 Voltage (V)

Calc – R2 Voltage (V)

Calc – R3 Voltage (V)

Calc – R4 Voltage (V)

Calc – R5 Voltage (V)

6 12

Simulate: Observe Voltage Drops You will use Multisim Live to simulate a circuit with 6 V and then 12 V of supplied voltage and record the voltage drops at each component, as well as the total current.

Instructions: Simulate the Circuit and Take Measurements 1. Access Multisim Live circuit Kirchhoff’s Voltage Law at: https://www.multisim.com/content/uqgFk7y8bwjnDH9E6zYGoA/kirchhoffsvoltage-law/.

Note: It uses a 6 V DC power supply to provide voltage across 5 resistors. 2. Click Run to begin simulating the circuit. 3. Measure the voltage detected by the voltage probe for each resistor.   

Note that each probe measures voltage in reference to the nearest voltage reference point. Open Split view to see the charted values of the voltage dropped at each resistor. If needed, adjust the scale of the graphing window.

b) Record the measured voltages in the appropriate section of the table below.

Vs (V)

Meas – Total Current (mA)

Meas –R1 Voltage (V)

Meas –R2 Voltage (V)

Meas –R3 Voltage (V)

Meas –R4 Voltage (V)

Meas –R5 Voltage (V)

6 12

Task 5) Implement: Measure Voltage Drops

You will now go beyond simulation and use the NI ELVIS III to confirm the principles expressed by KVL. You will build a circuit with three series resistors and test with a random supply voltage to see if the voltage drops add to the voltage supplied to the circuit.

Instructions: 1. Connect the following circuit: 

Remember to turn off the protoboard while wiring.

Figure 1-1 Basic breadboard configuration for a simple series circuit

2. Turn on the NI ELVIS III and ensure it is connected to your computer.

3. From the Instruments tab of Measurements Live (https://measurementslive.ni.com/), open the following instruments:  Digital Multimeter (DMM)  Variable Power Supply (VPS), 0-15 V DC (Power Supply). 4. Adjust the variable power supply (VPS) to any voltage value. 5. Measure the voltage across each resistor in the circuit using the DMM.

Figure 1-2 Configuration for measuring the voltage drop across one resistor

6. Add the three voltage drops together.

a) Record the measured voltage drops and total voltage in the table.

Measure – R1 Voltage (V)

Measure – R2 Voltage (V)

Measure – R3 Voltage (V)

Sum of Measured Voltages (V)

VPS Reading (V)

Kirchoff’s current law (KCL) Task 6) KCL Measurements

You will use circuit laws to calculate the total current and the current at each resistor when you add resistors in parallel to a circuit. Later, you will observe these values experimentally and compare your measurements with the calculated values.

1. For Circuit 1, shown below, calculate the total resistance, the total current in the circuit, and the current through each component.  Recall that voltage in parallel components is equal.

Circuit 1: Begin your calculations with this simple parallel circuit

2. Add another parallel 3.3 kΩ resistor to the previous circuit to form Circuit 2. Recalculate total current, total resistance, and current through each resistor.

Circuit 2: Add a parallel resistor

a) Record your calculated values in the Table. Circuit

Calc – Total R (Ω)

1

Calc – Total I (mA)

Calc – R1 I (mA)

Calc – R2 I (mA)

Calc – R3 I (mA) N/A

2

Implement: KCL Circuits Now, you will build the circuits presented in the calculation exercise and take actual measurements of the values for which you calculated theoretical values.

Instructions: Set up the Circuit

1. Connect the following circuit (Circuit 1 from the Exercise stage):  Remember to turn off the protoboard while wiring.

Figure 1-7 Breadboard configuration for Circuit 1

2. Turn on the NI ELVIS III and ensure that it is connected to your computer. 3. From the Instruments tab of Measurements Live, open the following instruments:  Digital Multimeter (DMM)  Variable Power Supply, 0-15 V DC (Power Supply)

Circuit 1

1. Measure the total circuit resistance using the DMM in resistance mode. Record your results in the table. 2. Set the VPS to 12 V. 3. Measure the total circuit current and current at each resistor using the DMM.

b) Record your measurements in the table. This table is to be filled out as you perform this task. Circuit

Meas. – Total R (Ω)

Meas – Total I (mA)

Meas – R1 I (mA)

Meas – R2 I (mA)

Meas – R3 I (mA)

1

N/A

2

Figure 1-8 Configuration for measuring total current

Figure 1-9 Configuration for measuring current in first branch

Figure 1-10 Configuration for measuring current in second branch

Record your measurements in the appropriate locations in the table.

Circuit 2: 1. Add another parallel 3.3 kΩ resistor to the previous circuit to form Circuit 2.

Figure 1-11 Breadboard configuration for Circuit 2

2. Repeat the measurements you took for Circuit 1 (total resistance, total current, and current at each resistor).

Figure 1-12 Configuration for measuring current in middle branch

Record your results in the table.

Task 7) Suppose that you are going to measure Vs with a voltmeter, as shown in the figure below. To have an accurate measurement, the output impedance ROut (from the voltage source) and the input impedance RIn (into the voltmeter) should be selected so that one is small and the other is large. Which should be small, and which should be large? Why?

ROUT − +

Voltage Source

RIN

Voltmeter...