ECE 201L Circuit Analysis Laboratory
Lab 10

This lab provides experience with digital logic input/output, quad NAND gate (configured as inverter), and the data acquistion board (DAQ)

Do the following exercises. Report your results by writing a Word document and submitting it to Isidore. Submit one report per group.

A logic indicator is a circuit that lights an LED for a logic HI (5 V) input, and leaves the LED dark for a logic LO (0 V) input. These two states can be represented in the following diagrams. A design that implements this circuit is shown next to the diagrams. The components are a 330 ohm resistor, LED, 10k ohm resistor, and 2N3904 npn transistor.

on off

The diagram below suggests how the components might be arranged on a prototype board. The data acquisition system provides power to the circuit. Connect pin 5 (CH1 LO) to pin 6 (AGND).

Construct the logic indicator and test it by connecting the input to 5 V and to ground. Measure the voltage across each resistor when the indicator is on, and use Ohm's Law to determine the corresponding currents.
A logic switch is a circuit that allows the user to set a logic value to either a logic HI (5 V) or a logic LO (0 V). These two states can be represented in the following diagrams. A design that implements this circuit is shown next to the diagrams. The resistor should be between 10-50 KΩ

On Off

Connect logic switches and logic indicator as shown below. You will eventually need three switches, only two are shown here, and only the top switch is used in this exercise.

Connect the circuit to the DAQ. Turn the top switch on and off and confirm that the LED turns on and off. Collect strip chart data showing the switching behavior.
Find a 4011 Quad NAND chip in your parts box. The pin diagram for this chip is reproduced below.

Remember to connect power (5 V - DAQ pin30 - to chip pin 14) and ground (GND - DAQ pin29 - to chip pin 7). Connect DAQ pin 2 (CH0 LO) to DAQ pin 3 (AGND).
Construct the following inverter circuit using one of the nand gates

Connect V_in to the top switch and to pin 1 (CH0 HI) of the DAQ. Connect the output V_out to pin 4 (CH1 HI). Connect pin 5 (CH1 LO) to pin 6 (AGND).
The diagram below shows how the breadboard might look, but is not the only way of arranging the components.

Use the strip chart to display channels 0 and 1 as you manually toggle the switch. Observe and describe the pattern of the indicator light. Include a plot (or screen shot) of the strip chart.
Replace the input switch with a potentiometer circuit, as shown below.

The potentiometer, or trimpot, is shown below.

Collect strip chart data as you vary the potentiometer over its range of motion. Plot the output voltage from the strip chart as a function of the input voltage of the strip chart. This is the transfer curve of the inverter. Identify, as best you can, the voltage at which the inverter switches and the LED turns on or off.
Build a “night light” using your light-sensitive resistor, a nand gate, and LED indicator. Choose the resistor R₂ to provide an appropriate switching point for your light-sensitive resistor. The LED should go on when you shde the sensor with your hand and off when you uncover the sensor. Use the strip chart recorder application to record the input to the nand gate and the output from the nand gate. Also demonstrate to one of the lab assistants.