On Mon, 04 Feb 2008 11:28:43 -0500, default wrote:

:I was at the hardware store shelling out $20 for an "infinite range
:control." It is a proportioning control for an electric range burner.
:It is primitive. A small 3 W heating element warms a bimetallic
:leaf which moves a set of contacts, which opens the connection to the
:range element and modulates the power.
:
:I'm thinking it is stupid to keep replacing these things . . . I go
:through one a year and its a hassle to change out or repair a broken
ne.
:
:What's the consensus on getting an ordinary $3 lamp dimmer and putting
:a 40 amp triac on it and using that for element control? Anyone see
:why it shouldn't work or what to look, look out for?
:
:I've got a half dozen 40A 600 V triacs already mounted to heat sinks
:that I got for free. Plan A: would be to just open the lamp dimmer
:and wire the Triac in place of the one inside, and mount it outboard
n its heatsink. Perhaps changing the size of the phase shift
:resistor to accommodate 240 instead of 120.
:
:Plan B: But how about using the 120V lamp dimmer as-is? I would just
:use it to trigger the heatsink mounted triac. Any idea if that
:could/should work?
:
:Any downside to using a phase control element instead of
roportioning? Would it cause my power bill to go up?
:
:I figure I could do it safely.

Ideally, heater elements with triac switching should employ zero-crossing power
control.

This Philips (now NXP) application note shows in 6.2.3 the use of a dedicated
time proportional triac controller ic (TDA1023) for heater element control. In
your case the circuit of Fig.14 would be required.
http://www.nxp.com/acrobat_download/...es/APPCHP6.pdf