If you need to produce tones or test amplifier circuits, you can build your own audio oscillator. An oscillator produces electronic signals in the frequency range of human hearing, roughly 20 to 20,000 Hz. While making an oscillator from scratch can become involved, the XR2206 integrated circuit, or IC, contains most of the necessary circuitry. The IC requires only a few outboard parts and produces sine, triangle, sawtooth and pulse waveforms. You can adjust the oscillator's frequency over a wide audio range.
- Skill level:
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Things you need
- 1K-ohm ¼-watt resistor
- 2M-ohm variable resistor
- 30-watt soldering iron
- Electronics solder
- Prototype breadboard
- XR-2206 function generator IC, dual-inline package
- 200-ohm ¼-watt resistor
- .05-microfarad 50-volt capacitor
- 2 1-microfarad 50-volt capacitors
- 2 5.1K-ohm ¼-watt resistors
- 10-microfarad 50-volt capacitor
- Assortment of #22 gauge jumper wires
- 9-volt battery
- 9-volt battery clip
Solder one lead of the 1K-ohm resistor to the centre lug of the 2M-ohm variable resistor. Solder a 2-inch 22-gauge wire to one of the variable resistor's remaining lugs.
Insert the XR-2206 integrated circuit into the breadboard so it straddles the horizontal channel in the board. Insert the free lead of the 1K-ohm resistor from step 1 so it connects to the IC's pin 7. Insert the wire on the variable resistor into an unused column in the board.
Insert the leads of the .05-microfarad capacitor so one connects to pin 5 and the other to pin 6.
Insert the leads of the 200-ohm resistor so one connects to pin 13 and the other to pin 14. Insert one lead of one 1-microfarad capacitor so it connects to pin 4. Insert the other lead so it shares the column with the variable resistor's connecting wire. This column serves as a grounding point for the circuit.
Insert one lead of the second 1-microfarad capacitor so it connects to pin 10. Insert the other lead so it shares the grounding column with the variable resistor wire and capacitor lead. Insert a jumper wire to connect pin 12 to the grounding column.
Insert one lead of a 5.1K-ohm resistor so it connects to pin 4. Insert the other lead into a free column. Insert the red wire from the 9-volt battery clip so it also connects to pin 4. Insert the black wire from the battery clip so it connects to the grounding column.
Insert one lead of the second 5.1K-ohm resistor so it shares the free column with the first 5.1K-ohm resistor. Insert a jumper wire so it connects this column to pin 3. Insert the resistor's other lead so it connects to the grounding column.
Look at the 10-microfarad capacitor and notice one lead is positive and the other is negative. Insert the negative lead into the grounding column. Insert the remaining lead so it connects to the IC's pin 3.
Insert a jumper wire of at least 10 inches to connect to pin 2. Clip the oscilloscope's probe tip to the free end of this wire. Insert a second long wire to connect to the grounding column. Clip the oscilloscope probe ground to the end of the second wire.
Snap a 9-volt battery into the clip. Turn the oscilloscope on. Set its sweep rate to 5 milliseconds per division. Adjust the vertical sensitivity until you see a sine wave on the oscilloscope screen.
Tips and warnings
- When inserting the IC into the breadboard, make sure all the pins go straight into the board.
- By disconnecting the 200-ohm resistor, a triangle wave will appear at the IC's output pin 2.
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