Discussion in 'The Projects Forum' started by zohonie, Jan 20, 2011.

1. ### zohonie Thread Starter New Member

Dec 2, 2010
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0
I would like to find the easiest way to create an adjustable square wave. The wave needs to be centered at 2.5 V. The magnitude of the wave must be adjustable between 0 and 5 v by a potentiometer. The frequnecy also adjustable between 0-4Hz also by a pot. I'm very new to electronics so please be specific in your explaination. It would be best of there is a commerical board that can do this. Thank you.

Last edited: Jan 20, 2011
2. ### Wendy Moderator

Mar 24, 2008
21,352
2,919
A simple 555 circuit with an output pot and cap will do this. What kind of load are you driving? No time now, but I'll be glad to throw a quick schematic up in a couple of hours.

3. ### Wendy Moderator

Mar 24, 2008
21,352
2,919
OK, there is no specific board that will do then that I know of, but there are many things I don't know.

555 Hysteretic Oscillator

And add this to the output...

An even better square wave can be made by using this schematic...

Make R1 very small compared to R2 (say 1KΩ/100KΩ)

eric3404 likes this.
4. ### tom66 Senior Member

May 9, 2009
2,613
218
If you want a 50% duty cycle I'd recommend either adding a flip-flop to the output of the 555 or using an op-amp oscillator.

5. ### Wendy Moderator

Mar 24, 2008
21,352
2,919
No need, the latter schematic will achieve better than 50.1% with the ratios described. Ever done the math?

A hysteretic oscillator using a CMOS 555 will also be very square.

6. ### thatoneguy AAC Fanatic!

Feb 19, 2009
6,357
727
When you say "level from 0-5V", do you mean swings from -2.5 to +7.5v, or swings from 2.5V (0V) to 0-5V? In other words, is the 0-5V peak to peak, or change from the 2.5v bias?