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Topic: NTC Thermistor readings varying... (Read 2 times) previous topic - next topic

Savers

Afternoon, I'm having some issues with my NTC thermistor and would appreciate some extra input.

I have calibrated the thermistor, and it should switch on and off a heat source according to the temperature.

After some tweaking, I was able to get the environment to stabilize at around 29 degrees on both the thermistor reading and the manual mercury-like thermometer.

It was fine a few days ago. Now I have returned to it, switched the circuit on again, and after leaving to stabilize I discover the manual thermometer is reading 25 degrees, but the thermistor still reading 29!?

This has happened a few times now. I'm certain there is no differing power drain caused by other entities in the circuit.

Any ideas?

felis

/felis

Savers



Servo is not currently connected, latching relay triggers the 12v heat circuit.

retrolefty

Any difference in power source from prior run to present run?

Lefty

Savers

#4
Feb 22, 2011, 04:31 pm Last Edit: Feb 22, 2011, 04:34 pm by Savers Reason: 1
Thats the trail of thought I originally had, but I'm using the USB on my laptop. Then I remembered the arduino has a 5v regulator built in so it couldn't really be the power source anyway unless using AC opposed to DC. I have also tried a 5v DC USB wall plug, to which it is still not reading correctly.

Connecting the thermistor to a spare output pin instead of the power rail on the breadboard would give the full 5v regardless would it not?

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