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Circuits sharing thermistor

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Hi,

can two circuits share the same thermistor?

I have a 220V controller for normal operation and a 12V circuit for travel. The two circuits will never work together at the same time. Connector X2-1; X2-2 is where the thermistor fits in. Connector X3 is the pot for setting temperature.

Circuits attached.

Cheers
Andrew
 

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ke5frf

New Member
I only see your 220 volt circuit, was there supposed to be another one?

But to answer your question (without really answering it), why not use a switch to move the thermistor (electrically) from one circuit to the other? If the two circuits are never operated at the same time, this should be a simple matter. A DPDT switch should be used, with the two thermistor terminals connected to the 2 common leads of the switch. The other four terminals will be going 2 each to your board inputs, with the normally closed pair going to one board and the normally open pair going to the other.

But to answer your question, in a nonspecific way, I do not think it wise to parallel two boards without a means of isolation like with a switch. The circuit impedances of the other board that parallel the thermistor (amplifier inputs, etc) MIGHT effect the overall resistance presented to the amplifier inputs of the other board. This would be bad since a thermistor is a resistance operating device. This is why the switch is a good idea.
 

Mikebits

Well-Known Member
Thermistors are cheap, why not use 2?
 

ke5frf

New Member
Thermistors are cheap, why not use 2?

I think I've read other posts from the OP about a travel trailer or camper or something of the like. Can't remember what kind of temperature control this is for, but it may be that he has already embedded his thermistor in his medium to be controlled, but that is a guess.
 
I think I've read other posts from the OP about a travel trailer or camper or something of the like. Can't remember what kind of temperature control this is for, but it may be that he has already embedded his thermistor in his medium to be controlled, but that is a guess.

They are independent and attached to the evaporator plate so I am OK, thanks.

Andrew
 
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