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Bob Widlar's hassler circuit

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devttys0:
Since Bob Widlar's infamous "hassler" circuit was never published, I thought it would be fun to design and build my own version based on the various functional descriptions floating around the internet. It's pretty simple, just uses a few op amps, but some people here might enjoy it!

There's a circuit description and demonstration video on my blog: http://www.analogzoo.com/2015/01/building-the-widlar-hassler/

Comments/suggestions welcome!

codeboy2k:
Welcome to the forum, and that was a well done video, thanks for sharing.

I watched it all the way through, and I didn't see the demonstration .

Maybe it was always on, and I'm just too old to hear 15 - 20Khz anymore :(

dannyf:

--- Quote ---There's a circuit description
--- End quote ---

U1a is a rectifier: its output goes up with the loudness sensed by the mic.

U2 is a schemitt trigger: it turns on more with louder sound;

U1b is an oscillator.

Q1/Q2 are two power AND gates.

Dongulus:
Now build one using a microcontroller ;)

dannyf:
It shouldn't be hard:

1) configure a high-frequency pwm generator. its output to a mosfet via a resistor;
2) configure a low-frequency pwm generator. its output to the joint of the mosfet + resistor;
2) adc the input and use it to control the duty cycle of the low-frequency pwm generator;
3) done.

A 8pdip attiny should be sufficient. Or a 20 cent stm8.

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