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Hacking AC thermostat

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skmdmasud

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Hi.
I have a situation where the AC temperature control unit is fixed to a specific temperature. I want to control the temperature to some degree. the temperature sensor used is a thermistor rated 1.5k at 22C. Can i place a 1k pot in series with the thermistor to change the temperature. Please suggest.


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alec_t

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Most Helpful Member
Assuming the thermistor is a NTC type, the pot in series should enable adjustment to a higher temperature, but not to a lower one. Is that what you want?
 

schmitt trigger

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To complement Alec's reply, if you want to lower the temperature, then a pot in parallel with the thermistor will do the trick.
I would use a pot with a value at least 10X that of the thermistor. And put a fixed resistor in series with the pot, such that the total resistance value NEVER goes down to zero.
 

alec_t

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That would work too. What temperature range are you interested in?
 

KeepItSimpleStupid

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If you did a few measurements we could figure out the optimum values. initially measure the resistance of the thermister at the fixed temp. Do the parallel combination at 20 and 30. 1/Rt=1/R1+1/R2....1/Rn for a parallel combination.
 
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