Electronics > Projects, Designs, and Technical Stuff
Bob Widlar's hassler circuit
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KM4FER:
Many years ago I started a new sysadmin job but there wasn't any work to do.  :-// 

The boss had bought me a brand new SUN workstation which was a real beauty so I spent my time messing about with it.  On either side of my cube were people who always spoke in loud voices.  It drove me crazy, I couldn't concentrate on anything, not that there was much to concentrate on.  So I wrote a program on the SUN to read the microphone input and detect high volume levels.   It didn't work very well since the mic was much more sensitive to me shuffling papers than the neighbors talking too loud.  Oh well, I learned a few things.

Three months of boredom and make work went by and I had just started to look for a different job when Management finally decided to centralize support.  For the next 15 years I was never bored nor had to find work to do.

georges80:
Amusing concept... More sophisticated than my high school prank.

Back in the dark ages (I was in high school, probably around grade 10) back in the early 70's....

I built an oscillator circuit and a mate & I installed it into a homemade pencil case. The bottom contained the circuit and the battery/speaker, the top had a false floor (to hide the goodies) and pencils etc sat up there. There was a microswitch that you could activate by sliding one pencil just far enough to push down on it and fire up the oscillator.

I sat at the back of the class (many knew I was an electronics nerd) and my mate at the front. He would activate the oscillator that of course was just high enough to be very irritating and non-directional due to bouncing off everything but low enough for the teacher to 'hear'.

Kids would turn to look at me, but my hands were up off the table and no link to me could be made.

I remember one class where the teacher was slowly becoming more and more irritable and some poor unfortunate student came in quite late, she totally lost it on the student who suffered her pent up wrath.

Aaah, the simpler times :)

cheers,
george.
Asim:
what's the current consumption of the circuit?
 I am tempted to build one as a pocket size and make it work of a battery.
_J_Herrmann_:
It's true, Widlar never published his circuit, but Bob Pease did a version of his own, and published it in the May 15, 1995 issue of Electronic Design, "What's All This Hassler Stuff, Anyhow?" See attachment. I redrew Bob's hard to read handdrawn schematic in LTSpice, and added info from RadioShack about the electret mic element and piezo speaker Bob referenced in the article at the end of the pdf. I personally haven't built it yet, it's on my to do list.
Cyberdragon:

--- Quote from: Dongulus on January 28, 2015, 11:03:53 pm ---Now build one using a microcontroller ;)

--- End quote ---

NEVER

I'll use tubes instead. >:D
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