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Triac circuit for controlling popper heater
bvwelch
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Posted on 12/28/2007 11:16 AM
Greetings,

Note: a "router speed controller" costs about $10, so building this circuit may not be cost effective. See the other threads here about the router speed controller.

I thought I'd share this circuit that works for me, in my modified air popper.

Instead of an off the shelf SSR, or a big heavy variac, I built the equivalent of an SSR with a 20 amp triac and a driver chip. Costs:

triac: $1.62 BTA20-700CWRG
driver: $1.16 MOC3041M

I used the schematic found in the datasheet for the driver chip.

Note- this triac needs a heat sink. And note especially that the "tab" on this triac is isolated for safety. I just mounted it on an aluminum project box with a little thermal grease.

I've started a web page for the project. Right now there is just a schematic for the triac:

http://bvwelch.co...


Bill
Edited by bvwelch on 01/18/2008 6:19 AM
 
seedlings
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Posted on 12/28/2007 11:18 AM
There is interest! Is this something like what an electric stove uses to control the heat element?

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
bvwelch
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Posted on 12/28/2007 2:35 PM
The idea of this triac circuit is very simple-- to emulate the person manually turning the power switch on and off.

There are lots of different triac drivers. I don't claim to really know a great deal about them. But the two kinds that I ran across on this project are:

1. Random Phase. An example of this type would be a "dimmer" for lights. The "phase angle" of the A.C. is tinkered with to modify the duty cycle. You could use this for the heater I suppose.

2. Zero voltage crossing. This is the type I chose. You simply control a low-voltage input, and the triac driver takes care of the rest. You can literally just hook up a battery and clip leads and watch it turn the heater on and off. Keep one hand in your pocket.

I believe this circuit would work just fine with the fancy PID controllers, in place of an SSR.

I said you control it with a low voltage. Actually it is a small current -- 15mA for the MOC4031.

Bill
 
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