Re: Triac question

["Nick Austin" <nick.w.austin@xxxxxxxxx>]

On 9/24/07, Stuart Meier <stuartm2007@xxxxxxx> wrote:
>
> Hmm, yes, think of it as a simple dimmer (gate current developed via a
diac,
> capacitor, resistor combination) on full brightness. That should work
one
> way only, question is, can one omit the cap and the diac without
impinging

> on reliability.
>
> Stuart

This is a normal dimmer circuit:
http://www.geocities.com/tomzi.geo/dimmer/dimmer.htm?200725

The cunning bit is that the trigger voltage is derived from the TRIAC anode
voltage so that once the TRIAC conducts the trigger voltage drops to
zero.  What you need is a modification to this circuit that has two
triggers.  As far as I can tell you'll need more than a handfull of DIACs,
Rs and Cs to safely do this.

Incidentaly Ian's relay suggestion would look like this:
http://xs.to/xs.php?h=xs319&d=07392&f=lamp_switch_3.jpg
It's going to briefly shut off the lamp current each time the relay changes
but otherwise looks good to me.

Nick.


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