thermistors not registering correctly

Hello All,

I have been building a Prusa i3 rep rap printer with a RAMPS 1.4 Board.
So far I have built it and have been able to get the x,y and extruder working however I have not been able to get the Z axis working.
The stepper motors work if i put the Z motors onto y or x connector on the RAMPS board.

My other problem is that my thermistors wont register on the LCD screen. As soon as I turn on the power I get a ERR MAXTEMP BED error message as below.

I have connected the Thermistors for the BED as well as the Extruder to the T0 and T1 connections on the board. But I always get the same reading on the LCD as attached image



I have tested the thermistors with a multimeter and they both provide a read out when I cover the thermistor to heat it up with my hand the resistance drops which works as expected I assume.



Does anyone have any pointers on this? I know this might be two questions here but I am assuming that a failsafe in the software is turning the z axis motors off.

Please see a layout of my Board layout attached as an image.


Any help would be greatly appreciated.

thanks

Are you pololu's well adjusted ? Try to swap a working pololu in the Z slot. Pololus are fragile, maybe one's broken. You may have a short on your thermistor. Check cables and connexions.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

Hi Zavashier,

Thank you so much for the quick reply .

I have swopped the stepper drivers around and it seems that i am still getting the z axis problem.

I checked each connection and each thermistor but it looks like there is no power to the z axis at all when i tune the pololu's. i used the y axis pololu on the z axis and the z axis pololu on the y axis and the y axis still works.

any other suggestions?

Thanks again for the help

Hmm. Check your firmware configuration (or get a confing.h from a user of the same printer).

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

So guess what. Turned out to be a broken pololu. And then what's worse I unplugged it and then plugged it back in but just one pin too low and I fried the whole Ramps board. Serves me right for being sloppy.

Wish I could find a way to fix it . Or do I have to buy a new one

doing that generally puts 12v onto 5v lines... this tends to make all 5v thing very unhappy..

Sorry to say it new mega time. The ramps board itself may be ok, only the mosfets damaged, but they are replaceable Any other pololus that where plugged in at the time will also probably be dead.