How to Build 0-200Hz Square Wave Generator

There are several options but if you want quick and cheap try some of these.

more ideas

an-118

some more ideas

Alternatively, you could do something with PIC's, but that would require you to write some software as well.

For symmetrical waveform and wide frequency range I would use a pair of opamps. One as an integrator, and another one as a Schmitt trigger with symmetrical hysteresis loop (like an inverting amplifier, but resistors to non-inverting input).

However, 0 Hz is too much, but you may cover several decades such a way. Use Teflon capacitor and an opamp with FET inputs for the integrator.

For better temperature stability of frequency and an output voltage I would add to the trigger's output a voltage limiter consisting of a resistor and a thermo-compensated symmetrical Zener diode (a Zener diode in a diode bridge).

If you really need to go from zero Hertz, you should use a pair of oscillators, and multiply their outputs on each other to get a signal with frequency equal to frequency differences, then divide it's frequency by 2 using a one trigger counter, for output signal symmetry.

I hope it helps.

Anatoliy Lisovskiy (AKA Wavebourn)

http://wavebourn.com

As you have described the problem I may suggest some solutions:

Use a cmos 555 (the intersil datasheet has a 50 % waveform generator circuit) and you can get a very wide range from it. Fast quick and I've used it for very wide ranges.

Should you need all the square waves to track in frequency, check out a johnson (twisted ring) counter. That will get you quadrature squarewaves at the cost of a cmos 4027 IC.

Or

Use something like an Atmel atMega or atTiny part - the counter/timer function can get you there fast, tools are free, and extensive app notes make the coding easier.

A bonus is the UART so you can use a terminal.WinAVR is free, and the demo software allows you to dynamically change the brightness. Most of the code is written. You need to program the board (the Dragon is 50 USD). If you use a bigger USB part, you can control it like a serial port. (and do that development later)

Somewhat off topic; There is something called a phase sequence array that is used for developing quadrature signals over an audio band for Single Side Band operation. That might be useful for controlling things too - but now you're entering real design...

You will have more questions, try leopoldvan AT hotmail Period com.

Hope this helps.

GLvA