Simple function generator for LM555

It is a simple function square, triangle and sine (or sine-like) generator with few frequencies up to about 30kHz.



After tests, the system was simplified like this:



5 such converters were made for each of 5 frequencies.
Resistors are mounting potentiometers used as adjustable resistors. Capacitors were experimentally selected to each 5 frequencies generated by 555 (500Hz, 1,5kHz, 5kHz, 15kHz, 30kHz). Frequencies were changed by adding a capacitor in parallel by what its capacity was enlarging. The power supply, generator and converters unit were made on one plate. A power amplifier which was stuck before on TDA 7394 plate was used as an amplifier:



The most important problem was switching the frequencies and work modes (sine, triangle, rectangle). Also rotary switches on the PCB were made:



A housing was made of an old ATX.
Ready grills were cut from the car RO housing, painted black with spray.




This is how it looks after assembling:



The parameters of the generator
Frequencies:

• 0,5kHz
• 1,5kHz
• 5kHz
• 15kHz
• 30kHz

Amplitude: continuously adjustable at the amplifier input (0-1V).
Generated waveforms: square, triangle, sine-like.
With external power supply, the generator works properly.
Here are photos of waveforms:



Link to original thread – Prosty generator funkcyjny na LM555