New lamp dimmer application?

[default]

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.
--

 

[default]

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.

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.


--

 

[Ecnerwal]

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.

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.

 

[James Sweet]

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.
--

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.

 

[Ecnerwal]

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

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...

 

[N Cook]

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 ?

 

[default]

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...

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

 

[James Sweet]

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.

 

[Allodoxaphobia]

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.

 

[whit3rd]

Sounded like you already had it figured out. Replace the triac ...
and give it a go.

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.

 

[James Sweet]

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.

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.

 

[Ross Herbert]

::>
:> :> >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.
:> > --
:>
:>
:> 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.

 

[Ross Herbert]

: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.
:
lan 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/applicationnotes/APPCHP6.pdf

 

[Bob Monsen]

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

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

 

[default]

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.
--

 

[James Sweet]

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.

 

[default]

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.
--

 

[default]

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.

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.


--

 

[whit3rd]

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.

 

[Mark]

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.  

--- Hide quoted text -

- Show quoted text -

I'd worry about 2 things..

1)lots of EMI generated from 50 Amp pulses floating around

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