Simple fail proof overtemp protection
Simple fail proof overtemp protection
(OP)
I've got an AC circuit that draws about 2A. What I need to do is cut the power to the device should a transistors heat sink overheat (defined as >100C). Preferably until the user unplugs the unit, or at least until it cools down some amount (20C?). It should be resettable, not permanent.
Simple solutions are usually the best, but unfortunately digikey only carries a to-220 thermal switch that can handle 1A, not the 2A required.
So I was thinking of either finding a way to boost the current capacity of it, or building a comparator with a NTC/PTC resistor and a voltage divider to set the trigger point. Maybe controlling a triac? I don't remember how triacs work; never even used one.
Any "battle tested" suggestions would be most helpful.
Simple solutions are usually the best, but unfortunately digikey only carries a to-220 thermal switch that can handle 1A, not the 2A required.
So I was thinking of either finding a way to boost the current capacity of it, or building a comparator with a NTC/PTC resistor and a voltage divider to set the trigger point. Maybe controlling a triac? I don't remember how triacs work; never even used one.
Any "battle tested" suggestions would be most helpful.





RE: Simple fail proof overtemp protection
http://www.sensata.com/about/klixon.htm
http://www.farnell.com/datasheets/95815.pdf
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I don't have an attitude problem. You have a perception problem...
RE: Simple fail proof overtemp protection
I think the polyswitch won't work; I haven't seen one that can handle both the voltage and the current (1-2A@90 up to 240Vac)
RE: Simple fail proof overtemp protection
xnuke
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RE: Simple fail proof overtemp protection
RE: Simple fail proof overtemp protection
xnuke - thanks! That's certainly another option to look into.
RE: Simple fail proof overtemp protection
You control the transistor's base/drive NOT the main switched power.
Does this thing have a micro controller involved?
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Simple fail proof overtemp protection
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Sometimes I wake up Grumpy.
Other times I just let her sleep!
RE: Simple fail proof overtemp protection
Last defence is what fuses are for.
Having a temp switch that maybe turns your problem ON and OFF randomly is not a solution.
If you need last defence protection you need a thermal fuse.
They make transistor based circuit breakers now.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Simple fail proof overtemp protection
RE: Simple fail proof overtemp protection
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com