 # Circuits with Multiple Sources

## Introduction

In this activity, we will be working with a circuit that contains multiple sources. In order to provide the necessary voltage to these sources, we will need to utilize the Analog Discovery's™ Arbitrary Waveform Generator (AWG—denoted as the W1 and W2 connectors on the Analog Discovery). We will explain how to properly adjust the AWG's constant voltage level in this exercise.

##### After you're done, you should:
• Be able to create a physical circuit with multiple sources from a schematic

## Inventory:

Qty Description Typical Image Schematic Symbol Breadboard Image
1 1kΩ resistor   1 10kΩ resistor   1 20kΩ resistor   ## Procedures

### Step 1: Understanding the Circuit

#### A. Circuit Schematic

1. Use V+ to apply 5V across the circuit.

2. Use W1 as the second source to apply 3V across the circuit (we will demonstrate how to set the W1 connector to the proper voltage level further through this project).

3. The resistors limit the current.

#### B. Add Current Measurement to Schematic for

1. In order to measure the current I1 , we need to re-configure the circuit to put the ammeter in line with the 1kΩ resistor.

2. The schematic to the right shows placement of the ammeter.

#### C. Indicate Nodes on Schematic for I1

1. Label nodes (A, B, C, D, E) as points that connect two or more circuit components.

2. Each node on the schematic corresponds to a separate row of holes on your breadboard.

#### D. Assign Nodes to Breadboard Holes

1. Arbitrarily pick different rows of holes in the breadboard and assign them to the nodes identified in part C.

#### E. Create Circuit for I1

1. Make the connections shown on the schematic of part C by inserting the component leads in the breadboard:
• The DMM's µA mA terminal and the V+ connector are at node A.
• The DMM COM terminal and the 1kΩ resistor are at node B.
• The 1+ connector, the 1kΩ resistor, the 10kΩ resistor, and W1 connector are at node C.
• The 1- connector, 20kΩ resistor, and the 10kΩ resistor occupy node D.
• The 20kΩ resistor and the Analog Discovery ground are connected at node E.

### Step 2: Set up Instruments

#### A. Open Voltage Instrument

1. Open WaveForms™ to view the main window.

2. Click on the WaveGen instrument icon to open the Arbitrary Waveform Generator window.

3. Open the Voltage instrument.

4. Open the Voltmeter instrument under the More Instruments Menu to display the measured voltage.

#### B. Adjust the Arbitrary Waveform Generator Settings

1. Select the Constant wave under the Basic tab.

2. Set the Offset value to 3V.

#### C. Apply Power and Make Measurements

1. Turn on power to the circuit.

2. The above screenshots are of Digilent WaveForms running on Microsoft Windows 7.
3. Turn on power to the W1 by clicking on 4. Your measured voltage should be approximately 1V.

5. Your measured current for I1 should be approximately 2mA.

Sometimes it is necessary to measure the amount of current at several different points in a circuit. At times, this process can be a bit frustrating if you do not fully understand how to break apart the circuit in the correct places. We will explore how this process is done by assigning a second current to be measured in the same circuit we just worked with. Proceed through the following steps to find out how this is done.

#### A. Setup the Circuit to Measure the Current I2

1. We've added the current I2 to be measured.

2. You should still have the circuit intact from when we measured I1 . We will only be making a few minor adjustments in order to measure I2 .

#### B. Add Current Measurement to Schematic for I2

1. In order to measure the current I2 , we need to re-configure the circuit to put the ammeter in line with the 10kΩ resistor.

2. The schematic to the right shows placement of the ammeter.

#### C. Indicate Nodes on Schematic for I2

1. Label nodes (A, B, C, D, E) as points that connect two or more circuit components.

2. Each node on the schematic corresponds to a separate row of holes on your breadboard.

#### D. Assign Nodes to Breadboard Holes

1. Arbitrarily pick different rows of holes in the breadboard and assign them to the nodes identified in part C.

#### E. Create Circuit for I2

1. Make the connections shown on the schematic of part C by inserting the component leads in the breadboard:
• V+ and the 1kΩ resistor are at node A.
• The DMM's µA mA terminal, the 1kΩ resistor, and W1 connector are at node B.
• The DMM COM terminal, the 10kΩ resistor, and the 1+ connector are at node C.
• The 20kΩ resistor, the 10kΩ resistor, the 1- connector are at node D.
• The 20kΩ resistor and the Analog Discovery's ground are connected at node E.

#### F. Apply power and Make Measurements for I2

1. Go through the process outlined in Step 2: Set up Instruments again, if necessary, to turn on the power supply to the AWG and voltage instrument.

2. Your measured voltage should be the same as before; around 1V.

3. Your measured current for I2 should be approximately 0.1mA.

### Challenge Problem

• If you are confident with your knowledge of multiple source circuits and would like some extra practice, we have provided an extra problem in the link below. This problem requires that you understand the concepts introduced throughout this exercise.