Cannot make the hotend or hotbed work

Hi everyone, I have a prusa i3 and I'm almost done building it, the stepmotors work perfectly and they all move correctly.
The problem I have found is about the hotend and the hotbed, I have tested them and they get hot if I apply electricity directly to them, but from the software trough the sanguinololu I cannot make them work.
I think the problem may be in the termistors. I have tested them and the conexions are good (I can read 100k ohm in my multimeter in the sanguinololu connection) and I don't know what else could it be.

I have uploaded a picture of the connection just to ask you guys if I need to connect 4 wires for each thermistor or 1 is enough (I thought one was enough but maybe the problem is there), and I also have uploaded a picture to show you my pronterface frontend, you can see that the thermistors returns no values when I check the temperature.

I'm using sprinter, and I have the latest sanguinololu version b.

thank you very much, if you need any other information I'll try to follow closely this post to update it asap

You need two wires per thermistor, not one or four.

You do need four wires for the bed though and I can see you have two connected. You need four and they also need to be thicker if you have the standard 10A bed.

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I think those are the power connectors. They supply the power to the hot end and heated bed. The thermistor connectors are on the other side of the board. You'll need to change the conector to a two pin connector since they are right next to each other.

Bryan

thank you for your answers

Quote
bryanandaimee
I think those are the power connectors. They supply the power to the hot end and heated bed. The thermistor connectors are on the other side of the board. You'll need to change the conector to a two pin connector since they are right next to each other.

Bryan

You're right, those are the power connectors, the thermistor connector are simple and I think there's no problem in that connection, but the problem may have been here

Quote
nophead
You need two wires per thermistor, not one or four.

You do need four wires for the bed though and I can see you have two connected. You need four and they also need to be thicker if you have the standard 10A bed.

I changed to a 4 wire connexion with a same size than the main power cable and the behaviour of the printer is the same than before, nothing changed.

Very simple test:

1) Check the thermistor temps with Pronteface. They should be close to your room temperature.
2) Unplug the thermistors one at a time. The thermistor temperature (for that input) should go to zero or something really low. It also might trigger a MINTEMP error.
3) Short the thermistor inputs (one at a time). That should trigger a MAXTEMP error.

In each error case you may have to reset the firmware and re-connect after the error is gone. If all 3 give the right response, it's a pretty good bet that the thermistor is ok.

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uncle_bob
Very simple test:

1) Check the thermistor temps with Pronteface. They should be close to your room temperature.
2) Unplug the thermistors one at a time. The thermistor temperature (for that input) should go to zero or something really low. It also might trigger a MINTEMP error.
3) Short the thermistor inputs (one at a time). That should trigger a MAXTEMP error.

In each error case you may have to reset the firmware and re-connect after the error is gone. If all 3 give the right response, it's a pretty good bet that the thermistor is ok.

I did the first check, and the temperature it says is just 3, i don't know what does it mean, you can see the screenshot commands i uploaded in the OP.
I'll check in the morning 2 and 3, thank you for your answer

When it says 3 it means 3C. That suggests that your thermistor is not hooked to the input you are watching.

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uncle_bob
When it says 3 it means 3C. That suggests that your thermistor is not hooked to the input you are watching.

You're right, it doesn't matter if I disconnect one thermistor, both, or if I short the thermistor inputs, it always says 3 on the temperature values
How can I fix that? I checked all the pronterface settings and the serial port settings and I'm not able to find any option related with the thermistor inputs.

Thank you uncle_bob!!

The thermistor settings are in the configuration.h file right at the top of the file. You need to know the type of thermistor you have and pick the corrrect table by the setting in configuration.h. It's the same file that you need to edit to get all of the mechanical stuff right (steps/mm, speeds, end stops....).

The other posability is that you are plugging the thermistors into the wrong port on the interface board. It's worth checking before you go to crazy with the firmware...

Edited 1 time(s). Last edit at 11/08/2013 11:08AM by uncle_bob.

Quote
uncle_bob
The thermistor settings are in the configuration.h file right at the top of the file. You need to know the type of thermistor you have and pick the corrrect table by the setting in configuration.h. It's the same file that you need to edit to get all of the mechanical stuff right (steps/mm, speeds, end stops....).

The other posability is that you are plugging the thermistors into the wrong port on the interface board. It's worth checking before you go to crazy with the firmware...

I've tried with is EPCOS 100k (what the seller told me) and also with standard 100k. in the first case (the one I had) it says T=3 for both thermistors, in the second case it just says T=0 for both thermistors.
About the plug in the interface board, I bought the board already assembled, so I think there is no chance to make a mistake, isn't there?

Edited 1 time(s). Last edit at 11/11/2013 07:54AM by aurican.

I also checked the thermistors with the ohmmeter and they are 100k (102k exactly)

The thermistor resistance is converted to a voltage by your board. The voltage is read and converted to a temperature by your firmware.

The board has a pull up resistor on it (4.7K or 1K or what ever). The firmware has settings for various combinations of resistor and thermistor. If they do not match up, you will not get 15-30 C as your room temperature reading. It sounds like your thermistors are correct.

A thermistor reading port with nothing attached to it will read 0C (lowest thing in the table). Having the thermistor to the wrong pins is the most likely problem. Shorting the thermistor pins together on the board should give you somethig > 300C and trigger a maxtemp error. Doing this is simply to confirm that you are working with the right pins. Another way to check the pins is to heat up the thermistor with a hot air gun / hair dryer. The temperature reading should go up pretty quickly.

If:

1) you are on the right pins
2) your board has a 1K pull up
3) your firmware thinks you have a 4.7K pull up

You will read 0C at room temperature. In that case you need to switch the firmware to a table that matches your thermistor and the 1K pull up.

Quote
uncle_bob
The thermistor resistance is converted to a voltage by your board. The voltage is read and converted to a temperature by your firmware.

The board has a pull up resistor on it (4.7K or 1K or what ever). The firmware has settings for various combinations of resistor and thermistor. If they do not match up, you will not get 15-30 C as your room temperature reading. It sounds like your thermistors are correct.

A thermistor reading port with nothing attached to it will read 0C (lowest thing in the table). Having the thermistor to the wrong pins is the most likely problem. Shorting the thermistor pins together on the board should give you somethig > 300C and trigger a maxtemp error. Doing this is simply to confirm that you are working with the right pins. Another way to check the pins is to heat up the thermistor with a hot air gun / hair dryer. The temperature reading should go up pretty quickly.

If:

1) you are on the right pins
2) your board has a 1K pull up
3) your firmware thinks you have a 4.7K pull up

You will read 0C at room temperature. In that case you need to switch the firmware to a table that matches your thermistor and the 1K pull up.

I just tried a few more configurations to see what happened. These are the results I got:

SENDING:M105
ok T:0 @:0 B:0
with 100k thermistor

SENDING:M105
ok T:3 @:0 B:3
with epcos 100k

SENDING:M105
ok T:0 @:0 B:0
with parcan 100k

SENDING:M105
ok T:0 @:0 B:0
with honeywell 100k

SENDING:M105
ok T:-20 @:253 B:-20
with mendel-parts thermistor


in all cases they are the same values when the thermistors were connected, when there were no thermistors connected, when I short the pins (i tried shorting 1 with 2, 2 with 3, 3 with 4 or even 1 with 3).

I'm starting to think that there must be some kind of bad connection in between the motherboard thermistor pins and some other element inside the mother board.
The processor is working fine and the stepmotors are working perfectly

here is a photo of the pins I numbered


Edited 1 time(s). Last edit at 11/12/2013 04:38AM by aurican.

Shorting the thermistor pins does not trigger a max temp error and give you a very high reading. Since you get 0C with things unplugged, that indicates you are not reading a thermistor on those pins. It's hard to know if it's a firmware problem or if the board is shot. If you believe the firmware is correct, that leaves the board being broken.

Hello,

Sorry to revive the thread after such a while but I'm having a similar problem right now (see here). I was wondering, did you manage to resolve the issue? Or was it a broken board?

Best regards,
Ming-Hua