20 Amp dimmer control?

I (we) use neat little dual burner hot plates on kitchen counter. Last 2 units we purchased (from a GEnerally reputable company), have dinky temperature contol settings, that are now defunct. They are difficult to repair. So now I have 4 burners and no reliable control.

1) What I need is a 20A dimmer (like a light dimmer), I'll use to set my temperature, advise here would be ok. I'm easy with building stuff like that myself, but maybe something is available 'off the shelf'.

2) Later, if necessary I'll put in a feed back from a thermistor, to set the temperature by duty cycling.

I should do #1 for the learning curve and see how it works 1st. Regards Ken

Reply to
Ken S. Tucker
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No. Those hot plates are meant for the duty cycle powering (and function) set-up.

They are poor efficiency wise, compared to gas (as it relates to getting the heat into your pot), so as you go down in heater coil temp, your transfer efficiency goes down even faster. I have always hated electric 'burners', but they make great learning tools to show what a little air does between your heat sink and your heat source.

Folks learn real quick when the IGBT is NOT properly mated to the heat sink on a design that actually does drive the thing. I had to RE-teach an assembler just how to be sure that he would achieve a co-planar mating plane across 24 large, hand soldered devices meant to all properly mate to a monolithic heat sink extrusion. He was unable to put the logic together that he had to mate them to the heat sink BEFORE he soldered them into place. After 2 units got smoked, the chief engineer told him to do it the way I showed him it had to be done.

I do so hate stubborn people, and when they are stupid, the problem is tenfold worse. I think they are tests God put before me to see how I handle them. Me and that little dork never did get along, because he was at the company before me, but couldn't handle the fact that I advanced through the company ahead of him. Typical electronics industry crap at that end. The folks at the other end are to blame though, because they won't shitcan poor 'help' and hire experienced professionals.

Reply to
BubbleSorter

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Take a look at figure 12 of:

http://www.littelfuse.com/data/en/Application_Notes/AN1003.pdf
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Reply to
John Fields

A SSR like this:

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with a heatsink can be driven by a 555 to do what you want.

Reply to
David Eather

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We have a number of quad DMX compatible dimmers in stock at

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Many thanks,

Don Lancaster                          voice phone: (928)428-4073
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Reply to
Don Lancaster

You're not going to make anything for less than a whole new unit

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Reply to
Fred Bloggs

Because of the long time constant of the burners, no need for phase control. Check out "integral cycle controls". You won't get EMI with these either. Output switch is on for N out of X cycles.

Reply to
Oppie

I wouldnt bother using triacs etc, a relay is more robust, just hook it up to a slow oscilator with adjustabel mark/space ratio.

If it were just for a one off experiment, eg to see what sort of power level corresponds to what cooking performance, a salt tank would be easier.

NT

Reply to
NT

to Bad you couldn't get away with using a 15 amp quadrac. A very simple method of doing what you need.

If seems the largest I can find are 15 amps.

Jamie

Reply to
Jamie

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Veni, vidi, potuit superare.
Reply to
John Fields

What's an "iffy" temperature control? Burners like these don't usually use temperature measurement feedback, they are open loop average power controls, and to this day still based on bimetallic action.

Reply to
Fred Bloggs

Using 2 controls for the 2 hotplates, 10 amps would do because the LARGER hot plate is only 900 watts.

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John G
Reply to
John G

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AGAIN, the bi-meltallics are SWITCHES and you get a DUTY CYCLE paradigm of operation, and the burners, when they are on are on at full wattage.

YOUR idea of pumping them with a lower wattage, variable feed is a bad idea because a hot plate is a poor efficiency device to start with, and that is why the burner, when it is active, is always FULL ON.

This works really great on a microwave,where the energy is always getting dumped into the work. So a slow heating by using direct time percentage duty cycle works great, done right.

A hot plate is so lossy to start with that pumping it with less energy avalanches efficiency on a different plot than the wattage.

You would take a LONG time to boil a pot of water, and it would cost you four times the consumption.

The reason? The AIR GAP between the burner face and the pot.

This is why inductive and direct coupled systems are far more efficient.

Reply to
Pueblo Dancer

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Maybe true when hot. When cold?

NT

Reply to
NT

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I think this is a bit of a false argument. Hotplates have lots of thermal capacity, and whether on-off cycled or more smoothly power controlled, they reach the same mean temp, as determined by the user adjusting the control.

NT

Reply to
NT

No, they do NOT.

Duty cycled, they do not "reach a mean temp". It is BLAST ON, idle OFF.

That is the only way to even approach efficiently getting heat into the pot.

Using a cooler coil by "dimming" it dims the entire system, which is already VERY inefficient.

It takes 2 minutes for a 900 Watt microwave to boil a cup of water.

It takes a 1500 Watt hot plate about 8 minutes with it being full on all the time.

Now, genius, you tell me where the energy got lost.

Reply to
Pueblo Dancer

I can only say that in my experience of using various types of electric rings, the modern solid hotplate type dont vary greatly in temperature while theyre cycled on and off. Other types are another matter: open coil types have far less capacity, bare wire elements have almost none, halogens have close to none etc.

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Beside the point really.

NT

Reply to
NT

IIRC you said you were looking for reliability and smoothness of control. Bimetal control almost gives you the best all round, the one shortcoming is the occasional failure, but long term failure rates are much better than electronic controls. If you wanted to optimise life expectancy of a new or recon unit you migth add a snubber across the contacts.

Bimetals heat the ring up to the required setting as fast as possible, dimmer-like control would ramp it up & down slowly, which is not very satisfatory for the end user.

NT

Reply to
NT

There was a recent thread on power supplies for mains LED lamps - 2 caps, and a bridge rectifier - in your case you would probably need to add a zenner diode and done. But I agree with the idea of using a bimetal thermostat as the best way.

Reply to
David Eather

No, it is exactly the point.

The full on heater works, BUT VERY POORLY SO.

So reducing the heat you put into the coil by reducing the voltage across it and hence the current in it makes it even worse at getting that heat to cross that air barrier. Since you are unaware of the air barrier, there is no way you are going to be aware of how inefficient it is.

In other words, you think it is beside the point because you are clueless as to what actually happens.

Otherwise you would understand that it is EXACTLY the point.

Reply to
Pueblo Dancer

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