New lamp dimmer application?

The range is old and I use it a lot - cooking and beer making are hobbies. That last can be hard on ranges.

AND I want an excuse to tinker with it.

If you go through one a year, then something is wrong with your range, or the power supply in your house. Our range must be 30+ years old, and I know for a fact that it has not needed any of these in the past 13 years, if ever.

Try it, see what happens, most range burners are 240V which may or may not be ok for the dimmer, but so long as you keep an eye on it I don't think anything too bad will happen.

As it happens, I make beer on mine. Invested in a "canning element" 13 years ago, put a 10 gallon pot on there and boil 8 gallons or so of wort down to 5, no problems with the range at all in 13 years. Catching the drips the exhaust fan can't keep up with and cleaning everything to suit me before I get started is more of a problem. The range, and the range controls, have had no trouble at all with this...

Add a snubber over the triac ?

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Well, I'm not looking for reasons why I shouldn't do it, but how to do it.

Sounded like you already had it figured out. Replace the triac with the bigger one, upgrade the wiring between the load and MT1 and MT2 accordingly and give it a go. You'll want a mechanical on/off switch as well, the one attached to the dimmer pot will be too small.

And, when you test/use it -- keep one hand in your pocket.

Not going to work, I suspect. The 'triac' in a light dimmer is actually a 'quadrac', which has a builtin trigger device, and isn't readily available in larger sizes. Phase control like in a light dimmer makes for non-flickering illumination.

But, you don't need any of that; the problem is just that long duty wears out the switch contacts, not that the few-seconds-on/few-seconds-off is a bad match for the heater interface. Your options are many: wire the replacement to a solid-state relay instead of directly to the load, or use an industrial-grade furnace controller (put a thermocouple sensor in your cauldron).

I have some mercury relays in my junk box that would give decades of service without a problem. Even simple contactor relays, if you use appropriate snubbers (I like surge-protector varistors for this duty) will last a long time compared to a consumer stove control.

There may be some like that, but all the light dimmers I've opened have a diac triggering a standard triac. A lot of times a lamp will fail and short the triac, so I've replaced them from time to time with whatever I had on hand.

:> > 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 :> > one. :> >

:> > 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 :> > on 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 :> > proportioning? Would it cause my power bill to go up? :> >

:> > I figure I could do it safely. :> > -- :>

:>

:> Try it, see what happens, most range burners are 240V which may or may not :> be ok for the dimmer, but so long as you keep an eye on it I don't think :> anything too bad will happen. :>

:>

: : :Add a snubber over the triac ?

Probably not required since the load is purely resistive.

: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 :one. : :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 :on 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 :proportioning? 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.

Triacs have different requirements for current at the gate. It's possible that your 40A triacs may need more current to trigger them than a dimmer will supply. However, why not give it a try?

Regards

The lash up works. I can control a 120 VAC lamp with the dimmer triggering the external triac. So at least it triggers on 120.

Before it goes into the range, I need some mounting washers for the triac. These are bolted to a bare heatsink and I'd rather insulate the triac than insulate the heatsink.

Still want to tinker a bit to see if the bare, out of the box, dimmer can be made to work the triac with only the two wires they supply.

Wire it up on 240 powering a couple of 200-300W incandescent bulbs in series, if that works then it should work fine with the burner.

I'll give that a try.

My current interest is to see how to get a lamp dimmer (pure out of the box, so to speak) to trigger a triac. It may be unnecessary, but there's some crud on the inside of the stove chassis; mostly rust and condensed oil - not too bad but what one might expect from a 30 year old, well used, kitchen range.

Anyhow, my reasoning goes like this - I see the stuff behind the panel and figure that the potentiometer in the dimmer might just die from crude ingestion (or significantly shorten its life).

I don't know about you, but I hate having to EVER repair something I designed and built . . . If the $3 lamp dimmer can be considered a component only, and work the secondary triac that seems better to me.

I'm still not ready to do any hardcore installation - no triac insulators and (one of the things I overlooked) no suitable "hard" means of breaking power to the element . I think it was you who said that - thanks. So I need a DPST switch capable of 10 amps ( and another hole through the porcelain finish to mount it)

This is way more fun than just going to the hardware store and shucking out money for another ancient design range control.

I have one burner that doesn't work now, so I can apply it as soon as I trust it. It hasn't worked for years but that's immaterial.

The idea of getting a hardware store lamp dimmer and mating it to a higher voltage higher power triac could have some commercial implications. Especially if it can be done without additional circuitry.

Most of the old stage lighting and centrifuge (industrial) stuff I've seen. A: they want you to buy the carbon pile/rheostat or variac to "fix it" and that costs hundreds or thousands of dollars. Or their "updated" controller that only cost hundreds++.

I'm guessing but the one or two theater's left with rheostat controls belong to Catholic schools or very old theaters.

Oh. Forget that stuff, I just want an option for my range.

Two things might be worth worrying about: first, the trigger of the new triac might be incomplete or unreliable (might miss some cycles); if you have an oscilloscope, it would be worth checking this. The current that triggered the old triac could trigger the new one only 90% of the time, or could miss negative half-cycles, or misbehave in lots of ways that wouldn't fail the lightbulb test.

Second, triacs have a dI/dt limit, so a heavy load should always be turned on/off at zero crossings (also for RF noise, but that's not tihe big issue). The failure mode if your phase-control trigger does too much switching at full current from a dead stop, is short circuit of the triac. Beware scorched wort! Solid state relays aren't terribly expensive, and include the desirable zero-voltage-switching.

I'd worry about 2 things..

2) if the triac shorts your burnner will be on full tilt and may be dangerous if you are not there, may want to include a mechanical overtemp saftey device. The triac could decide to short even when the burner is not in use when you are not home etc......

Maybe triac + mechanical overtemp saftey + mechanical on/off

The other failure mode I have seen is that the burner shorts to its outer shell and this is very bad becasue you can't turn it off because the burner stays activated by one side of the 240 line unless you have both sides of the line switched...

take care

Mark