Electronics > Beginners
Can a variable thermal shut off circuit be build?
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David Hess:
We have used the metal can AD590 as the temperature sensor for this sort of application in the past but they are pretty expensive.  The current output is easier to use.

I would build a latching circuit using the temperature sensor, a reference, and an operational amplifier as a precision comparator.  With proper calibration, the trip point can be set with a potentiometer and multimeter.

An external temperature trip might be a useful feature to build into a power supply.
FriedMule:

--- Quote from: David Hess on August 03, 2019, 03:18:32 am ---We have used the metal can AD590 as the temperature sensor for this sort of application in the past but they are pretty expensive.  The current output is easier to use.

I would build a latching circuit using the temperature sensor, a reference, and an operational amplifier as a precision comparator.  With proper calibration, the trip point can be set with a potentiometer and multimeter.

An external temperature trip might be a useful feature to build into a power supply.

--- End quote ---
The dmm idea sounds great, maybe even use one of the dmm displays from Ebay?

Yes and maybe in an electronic load, I am wondering on why that is not standard in the top of the range PSU / Loads.

May I put an enormous strange on your genres help? :-)
Could you maybe try to draw a schematic that I can start my project from?
David Hess:

--- Quote from: FriedMule on August 03, 2019, 09:24:55 am ---The dmm idea sounds great, maybe even use one of the dmm displays from Ebay?
--- End quote ---

That could work but I always just connected a multimeter temporarily to set the trip point.


--- Quote ---May I put an enormous strange on your genres help? :-)
Could you maybe try to draw a schematic that I can start my project from?
--- End quote ---

There is not much to draw.  Filter the signal and reference voltage before the comparator.  Using an operational amplifier makes this easier because of lower input bias current.

When I did it, I latched the output by using the operational amplifier to trigger an SCR which pulled the output to the load disconnect down to ground and kept it that way until reset.
FriedMule:
Thanks a lot, I'll try to se if I can draw something that do that:-)
Would you mind looking at it when / if I can draw it?
David Hess:

--- Quote from: FriedMule on August 03, 2019, 11:11:38 am ---Thanks a lot, I'll try to se if I can draw something that do that:-)
Would you mind looking at it when / if I can draw it?
--- End quote ---

Just post it.  Everybody will comment on it.
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