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Topic: MINTEMP error at first startup (Read 18193 times) previous topic - next topic

kengdahl

Most of the time the issue min temp is a bad connection.

If your unlucky the bad connection might be on the pcb, but it is unlikely.

dp_1

A little update:
I'm now going to receive the new ramps board as mine was broken.
In the meantime, I tested a bit more, reproducing the ramps thermistor circuit and marlin code on an arduino uno. This way there was nothing from the printer circuit, so nothing could go wrong.
I used a fixed resistance of about 110k ohm (3 x 330kohm resistors in parallel) as the thermistor and I could read a value of about 24 degrees.
Then I connected to the printer thermistor instead of the dummy one I made, and I could read a value really near the ambient temperature (21-22 degrees celsius).
If you want I can post a schematic of the circuit I used, so that if somebody else has the same problem he/she can check if it's the board or not.

I know, this may seem redundant, but I just wanteed to check if it really was the board being faulty or something else :).

dp_1
Prendete quello che dico come un suggerimento, non mi assumo responsabilità di nessun tipo

kengdahl

That would be great! Sharing knowledge is great!

dp_1

#18
Feb 18, 2015, 10:07 pm Last Edit: Feb 18, 2015, 10:13 pm by dp_1
Alright then, this is what I used for testing the thermistor.
I used another arduino just to be sure, you could probably use the printer one if it isn't broken. The schematic is attached, just connect the wire marked as "READ" to pin A0 of your Arduino board. The sketch I used is attached too, it is mostly taken from Marlin firmware.
In the schematic I used R2 for the thermistor, you can either use the real thermistor (right way) or a fixed resistance (why??? - the schematic and code are already tested :) ).
To use it, upload to the board and open the serial monitor, you'll read something like (values are fake, I don't remember them):

START
RAW:  560
TEMP: 54

RAW:  540
TEMP: 98

Raw values are simply read from the ADC, so they range from 0 to 1023, and temperature values are in celsius degrees.

This is mostly a copy-and-paste work, as the schematic is taken from the RAMPS board and the code is adapted from Marlin firmware.
If you need anything else feel free to ask, I'm more than happy to help :).
Prendete quello che dico come un suggerimento, non mi assumo responsabilità di nessun tipo

kengdahl

Oh. here is a pins.h with the pins switch if anybody else want to troubleshoot their shield:
https://drive.google.com/file/d/0B2bqiaE1rzP7akNja3VhU2lQOTAtVlBLSWl4blJraUNEUDRF/view?usp=sharing

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