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Looking for thermal cycling timer...


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Jan 29, 2004
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Any household gadget/appliance you may know using a 120-240VAC self-heated thermal timer like :

The bimetal changes N.C. to N.O. when its internal heater makes it snap. Then the internal heater is deenergized and after some time snaps back from N.O. to N.C. re-energizing the heater. Does not need an electrical load to do its cycling. Electric stoves 'infinite' hot plates controls do need a load to operate. Looking for one of those controls that can do its thing with no electrical load.

If you know of one such control, please advise. Yes, can be done low-voltage with a timer IC. About one cycle every minute or two is fine.

Kitchen oven, iron, room thermostate, water boiler, anti dew for mirrors, refrigerator ...

Aquarium heater. Mechanism is within glass so I believe it cycles on its own apart from water temperature.

Electric blanket. (Perhaps also heating pad.) Articles describe some types with cycling mechanism in the control box.

Hummingbird feeder -Message board describes cycling is independent of nectar temperature regardless whether bowl is dry or contains liquid.
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All answers are correct but I think Externet is looking for something that runs independently of its environment. All the suggestions so far are for thermostats that monitor the temperature of their surroundings.

My suggestion would be a resetting overtemperature trip bonded to a power resistor. Something like a shower TCO and a wirewound block resistor. If this is a timer circuit, you can bond more than one switch to the resistor.


Headline says: "Looking for thermal cycling timer...".
So the task is that it should be "thermal" but independent of "thermal" environment?

Why then "thermal" at all? Why not a simple astable multivibrator, a old car blinker relay..

@brian: (you say "monitor the temperture of their surroundings"
My old kitchen oven has the bimetal control uints on the front panel. They don´t have thermal feedback from the plate. But they work exactly like the picture of post#1. Basically they are adjustable PWM generators.

Yes, independent from environment temperature. The guts of the control timer/switch should provide the timing with or without load, as in figure at #1 Dismantled an electric stove 'burner' control and there is no heating resistor, seems the load current causes the heating of the bimetal by a non-copper conductor in series with the load.

The electric blanket control suggested may work if there is no bed temperature sensing feedback. Will explore types.

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