Schematic Wanted

Several decades ago I ran across a circuit as follows:

Uses a unijunction (not a PUT) to trigger a triac.

Input is mains 120vac. No transformer isolation. Isolation is not needed for my application.

Output is a single full sinewave with a long dead-time to the next full sinewave. As a potentiometer is adjusted, additional full sinewaves fill in the dead-time until full mains is output.

There is a slight dead-time at the start of each sine before the triac fires.

I am trying to find the schematic for this circuit. The circuit was published.

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Reply to
OldGuy
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I did that sort of thing to dim neon, back in my disco days in the early '80's... after frying several neon transformers with a phase-controlled drive >:-]

I didn't use a unijunction. I vaguely recall some optical thingy.

It's BC (before CAD) so I'll have to search my file cabinets for a paper drawing. I'll post if I find it. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

Nobody would use a UJT these days, we have zero crossing detector opto coupler triac drivers...

Reply to
bloggs.fredbloggs.fred

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How long?
Reply to
John Fields

Sounds like he wants pot-controlled variable duty cycle with full-cycle zero-switched output. Sort of like a solid-state infinite heat control.

Pretty trivial to do. It's possible to do reduce the periodic variations with a more modern approach (eg. sigma-delta).

Reply to
Spehro Pefhany

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Infinitesimal heat control? ;) 

Sort of, except that if he's doing integral cycle switching he'll 
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Reply to
John Fields

Aren't solid state light dimmers about six bucks ?

Actually they might just get cheaper because the work on incandescent lamps mainly.

Reply to
jurb6006

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