RAMPS/Arduino T1/T2 pins not working, T0 is okay

The thermistor cable snapped off from my heat bed and may have shorted something in the Arduino. It is not longer working.

From looking on the forums, it seems the Analog input on the Arduino is likely fried. I was hoping to use the T2 thermistor port to replace the dead T1 port, and tried to do so by switching the T1/T2 pins in the firmware (T1: 14--> 15, T2: 15-->14). It seems that the T2 pin is also dead. However, the T0 pin works just fine and connected the bed thermistor to this port works OK.

Is there any other, unused analog inputs which I could use for the heatbed thermistor? It would save me from having to replace the board.

Any help would be appreciated! Thanks

Edited 1 time(s). Last edit at 12/08/2014 05:08PM by geemoto.

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geemoto
However, the T1 pin works just fine and connected the bed thermistor to this port works OK.

I presume you meant T0 works fine, as that's what's in your subject. If not, I'm confused.

There are analog pins in Aux-1 and Aux-2 (diagram). You'll need to duplicate the circuit as it appears in the schematic. If you want to know why, read here.

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cdru

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geemoto
However, the T1 pin works just fine and connected the bed thermistor to this port works OK.

I presume you meant T0 works fine, as that's what's in your subject. If not, I'm confused.

There are analog pins in Aux-1 and Aux-2 (diagram). You'll need to duplicate the circuit as it appears in the schematic. If you want to know why, read here.

You're correct. Edited to fix the mistake. Thanks for the information, if I will use AUX-2 for example - by duplicate the circuit do you mean to simply connect pin 1 to VCC and pin 2 to GND? Or is there more to it then that?

Thanks!

Edited 2 time(s). Last edit at 12/08/2014 05:12PM by geemoto.

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geemoto
by duplicate the circuit do you mean to simply connect pin 1 to VCC and pin 2 to GND? Or is there more to it then that?

No, I meant with the resistor and capacitor. Look at the schematic under the Thermistors section. There's actually 3 duplicate circuits there, one for each thermistor. You''ll need to duplicate one of those with the correct value components in order to get a correct reading.

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cdru

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geemoto
by duplicate the circuit do you mean to simply connect pin 1 to VCC and pin 2 to GND? Or is there more to it then that?

No, I meant with the resistor and capacitor. Look at the schematic under the Thermistors section. There's actually 3 duplicate circuits there, one for each thermistor. You''ll need to duplicate one of those with the correct value components in order to get a correct reading.

Ah, got it! Thanks. It might just be easier to get a new Arduino at this point

I recently had the same thing happen on my Mega, but probably when the printer got plugged in. Interestingly, it was only the bottom half of the analog input 13 that was affected. Everything from the top half worked just fine. Also my A14 was partially affected in that the bottom 25% reads a fixed value.

I wrote a test program and looked at the raw data from reading a pot, and as I moved the pot slider the A13 line would read from a value of 35, then jump to around 600, then read in a linear fashion once the pot was over half way up.

A14 worked fine but seemed except for always starting at a floating value of 3-5. And A15 was not affected at all.

So out of curiosity, is there a way to provide ESD protection to the thermistor circuit? I assume the voltage or current spikes would come in through the VCC line?

Thanks

How can you kill an analog input?
You must have fed the thermistor pin with negative or >5V source? Did you short the 12V heatbed wire with the thermistor?
-Olaf

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o_lampe
How can you kill an analog input?
You must have fed the thermistor pin with negative or >5V source? Did you short the 12V heatbed wire with the thermistor?
-Olaf

This sounds pretty likely. I saw the thermistor leads were dangerously close to the 12V pads on the board - so it is pretty likely they shorted at some point. I covered the 12V pads with kapton tape to prevent this happening in the future.

Edited 1 time(s). Last edit at 07/10/2015 10:47AM by geemoto.

For myself, everything was working fine for two months or more - no active wire changes or anything else. Then one morning I went to print a new print and the temperatures were all messed up. That's when I started trouble shooting and determined that the A13 input to the Mega was messed up.

Also in my case the Mega is being powered via the USB cable and nothing else. D1 is disconnected on Ramps board.

The only unusual thing about my printer setup is - that I am running a 2.8 watt Laser diode using a JTech controller from the Fan output on D9. It has a physical connector to plug/unplug when I run the laser instead of the extruder. I had initially upgraded the MOSFETs right after I got the Ramps board to the Digikey IRLB8743PBF-ND MOSFET N-CH 30V 78A TO220AB

Thanks.

Lindsey

However, I am still wondering, if anyone out there knows of a way to provide ESD protection to the thermistor circuits?

Thanks,

Lindsey