Simple square wave function generator?

[MagnusBomba]

I would like to design a circuit that will generate a square wave of zero to 500Hz (preferably with 50% duty cycle). Should be adjustable by single potentiometer. Any suggestions? Thanks.

 

[Skogsgurra]

Easy if you forget 0 Hz.
The original application note on CMOS square wave oscillators is the RCA ICAN-6267 (from November 1973). Then, there is the good old 8038 and the 555. Even a 74HCT14 can be used if you exercise some care with feed-back resistors. Or just put a 2:1 divider after the oscillator. Or just google.
When do you want the circuit to go from "Hz" to DC?

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[roydm]

To get a nice 50% duty cycle generate 1,000 Hz then put it through a divide by 2 cmos chip,
Roy

 

[LionelHutz]

LM139

http://www.national.com/ds/LM/LM139.pdf

See page 12. Vary the 100k resistor.

 

[OperaHouse]

Another option is to use PWM switching regulator chip like the TL494, SC35XX ect. The frequency and duty cycle can be varied independently and the have considerable drive capability. For one of applications they can be found in many old computer power supplies that seem to be everywhere. I cut out the board with the chip and a few components with a cutoff wheel. Makes a fast breadboard for a project.

 

[fsmyth]

There is a ton of TL494 and 555 circuits at:

http://hmin.tripod.com/als/fsmyth/pages/timing.html

With careful selection of components, you can go to
0 Hz (i.e., off).
<als>

 

[GonzaloEE]

LM566, VCO IC. Not sure of the frequency range:

http://www.ee.ctu.edu.tw/material/data sheet/566.pdf