BioNB 440: Lab 7

Sine/triangle/square function generator.

Introduction.

In this assignment we will build and use an audio function generator capable of producing sine, triangle and squarewave outputs. The sinewave output will be gated to produce a cricket-like song.

Procedure:

The file timing1b.ewb uses two 555 timers to control a sine wave. When you build this circuit, assume that the plus supply will be +6 and the negative supply -6 volts. Use the 8038 described below to produce the 1000 Hz, 1 volt amplitude sinewave shown in the file. Be sure that the 4066 switch (and 555s) are running between +6 and -6 volts. You will have to use the variable voltage sources on the prototype board.

The sinewave will be produced from a commercially available function generator integrated circuit, the 8038. Refering to figures 5, 6 and 7 of the datasheet, and the schematic below. There is also a picture of the prototype board with the 8038 on it.

Note that in this and every lab assignment the verb build means to construct a circuit on the protoype board whith actual parts. The verb simulate means use Electronics Workbench mathematically simulate the circuit.

1. Build the circuit shown above. Attenuate the output about 10:1 using a 100K/10K voltage divider and connect the attenuated output to the microphone input of the computer. Adjust the sine distortion control and symmetry control for the best sine wave (most symmetrical and best shape). You may want to use a reference sine wave generated from Electronics Workbench to help adjust the circuit. How does the sine wave quality compare to the sine wave from the prototype board signal generator?
2. Build the chirp generator described in timing1b.ewb with the following specifications.

• Once per second produce a burst 200 msec long.
• Within the 200 msec burst length there should be 8-10 pulses with a 50% duty cycle.
• Each pulse should turn on a switch in a 4066 to produce a sinewave at the output of the switch.
• Remember that the output of the 8038 cannot go outside the power supply range of the 4066 switch
• Listen to the chirp using the computer speakers.

Your lab notes should include a schematic of the actual circuit you built.