Problem with reading temperatures

Hi,

I have Ramps v1.2. A while ago everything just worked fine. But recently my electronics won't read out my temperatures correctly.
Earlier my NTC 100K sensors were provided with 4.5V I guess, but now they only get 2V. I think thats the reason of wrong measurements. (125 degrees at room temp.)

How can I get it back to 4.5V, so the temperatures can be read properly? How did this happen?

I uses sprinter as firmware


Thanks!

Edited 2 time(s). Last edit at 11/13/2012 02:06PM by Bozzibo.

nobody?

Check the voltages on both sides of R7 (Thermistor 0) or R1 (Thermistor 1) in reference to ground. One side should be 5V. The other side is the thermistor/Mega input.

If you disconnect the thermistor and still get 2V, then I'd suspect that either C5 (Thermistor 0) or C8 (Thermistor 1) have an issue (eg: an internal short or dry cap?), or the pin(s) on the Arduino Mega have an issue (pins A2 and A1 respectively).

If the voltage goes close to 5V without the thermistor, then I'd suspect the thermistor is at fault. Could be that whatever you've attached the thermistor with has shorted the pins together. Also note that if the glass bead the thermistor is enclosed in breaks, you could get weird or incorrect readings.

Hope this helps.

Hi Cefiar,

I replaced C5 and C8, but without any result. Both were fine.

But I've connected only the Ramps board to 5V. When I do this, both T0 and T1 gets about 5v, which is perfect.
As soon as I place the Ramps on the arduino Mega 2560 it becomes 2.2v. So I guess there is something wrong with the arduino board, but I can't find what it is... The power pins are all fine, giving 5v, 3.3v, ...

If I use only the arduino board, pin A0 gives 5v, A1 = 0v, A2 = 0V and the other analog pins all give 0.3v. I Guess the pin a1, a2 are the problem?
Anything to do about that?

Hi Bozzibo,

I had a similar problem with my RAMPS v1.4. Twice. The temperature was fixed to a certain value in the software, and I found out the problem was with the Arduino Mega. Its output to the T0 in RAMPS wasn't working correctly, so I changed the pin map in the Arduino project to the T2 output. Now it's working just fine. I suppose it was a short circuit.
Using the Sprinter software I changed in pins.h and Motherboard=33 and Ramps = 1.3 the TEMP_0_PIN from 13 to 15 and TEMP_2_PIN from 15 to 13, compiled and voilà!

Hope this helps.