Heated bed, no temp

[perlguy 0]

I've installed one of the silicone heated beds from qu-bd.com (actually, not fully installed - testing right now).

I can get the bed to start heating up by issuing a "M303 E1 C8 S90" command, but I am not getting any readings from the thermistor.

I've installed the 4.7K-Ohm resistor onto R4 on the driver board.

Which pins should i connect the 2 thermistor leads to?

I've seen a picture that looks like you should attach them to the outer 2 connectors (SIG and GND). I've also seen a diagram showing the connection between 5V and GND.

I've enabled the sensors in the Marlin firmware and uploaded it to my board.

I just can't seem to get any data from the thermistor.

Any ideas?

Thanks!

 

[Daid 306]

Should be between SIG and GND, as the 4.7k resistor is between SIG and 5V (on the board)

 

[gr5 2,172]

Measure the thermister when it is not connected to the utlimaker board and make sure it measures around it's nominal value (very very roughly around 100K if it's a 100k thermistor - 50K might be normal also). Try to include all the wiring in your measurement - there may be an open (or possibly a short) in your wiring.

Heat up the thermister by touching it with your fingers or other heat/cool methods. You should see the resistance change immediately.

Once that is working, connect up the thermister to the ultimaker, turn on the power to the ultimaker. Now you have a resister divider so that the voltage at SIG should agree with this formula:

Vsig = 5V X Rthermistor / (Rthermistor + 4700)

 

[perlguy 0]

Had a bad thermistor.

Replaced it with a good one and all is well.

Thanks!