Re: Triac question

["Stuart Meier" <stuartm2007@xxxxxxxxx>]

Yes, Ian's circuit would do the trick, bar the quick flash. But a pair
of
Triacs will do the same. As with the dimmers, the trigger voltages comes
from precisely the same source, so it too drops to zero when it fires on
each half cycle. I guess I'm going  to have to build a pair and see. I'll
start with a standard basic dimmer and start eliminating components:-)

Stuart
----- Original Message -----
From: "Nick Austin" <nick.w.austin@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Tuesday, September 25, 2007 5:37 AM
Subject: Re: [ukha_d] Triac question


> 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.
>
>
> [Non-text portions of this message have been removed]
>
>