Folger Tech i3 Prusa: Heated print bed wiring

Alright, I've got the printer built, and it prints fine. But I could not figure out how to wire the hot bed, at all. Their instructions are not helpful as I was given REV B of the kit, while the instructions are designed for REV A. REV B comes with a different heat bed model than displayed in the instructions.

I understand I need to solder pads 2 and 3 together with the negative lead, pad 1 to the positive, and then put those two wires into the RAMPS board so the bed actually heats. My problem lies with the thermistor, it has 2 ends of wire coming out of one point. The instructions say I need to connect both thermistors (the print bed, as well as the hot end) to two ended pins, and connect that to the RAMPS board. If both ends of wire are going into the ramps board, how does it attach to the hot bed?

Any help is greatly appreciated, I've got the printer working, there is just a big curve in everything I print as the ABS filament warps while cooling.

. Stick the themistor in the hole in the center of the pcb and tape it down with Kapton tape.

When you put the sensor in the hole of the bed, make sure the wires do not make contact with each other or the aluminum of the bed.
The wires of the thermistor are not soldered anywhere on the heated bed.

-Olaf

This was one of head-scratchers I found in building this kit too. The instructions kind of leave you hanging here and in a few other steps.

You've prompted me to finally post my Folgertech Prusa I3 build cheat sheet, to document some of the, um, bumps in the road I encountered along the way.

Thank you very much for your help, I thought it had to be soldered to the board as well. It's working now, heating up and holding temperature, and my prints are coming out much better.

I think I have a bad heat bed or board, I have double and triple checked my wiring and still not heating at all....

Do you have a multimeter? Read the resistance between the heat bed leads . . . it'll tell you instantly if it is good or not.

- Tim

Okay it says 0.353 on the K setting of Ohms

If I hear you correctly, that would be 353 ohms, where it should be closer to 2 (yes, *two*) . . . Do you have a scale that is 200 or something along that line? It should read on your lowest scale, and if not your bed is either damaged, or mis-wired.

- Tim

It is a digital meter, there is an ohm reading and also the audible signal path, which I also checked and it did produce sound as an open circuit. I have rechecked the wiring multiple times now and it is correct. The heat bed is not working.

Most meters make sound on a closed circuit, not open . . . I'm still not quite certain what you are seeing . . .

Is it an autoranging meter, and it came up with the .353 K? Or ? ? ?

- Tim

Edited 1 time(s). Last edit at 06/25/2015 10:21PM by tadawson.

I am new to this 3d printing world so bare with me. I bought a folger tech prusa i3 kit and put it together. No big deals, went together fairly good. When I connect it to repetier host and try to get the heated bed to work, nothing. The motors move, the fan works and the extruder works. I even checked the power on the block when powering the heated bed up and nothing. That is problem #1, next thing is I bought the full graphics controller with the sd card slotand plugged it in. All I get out of that is a blue screen, if I flip the connectors it screams at me with a different colour screen. I have changed settings in marlin but it didn't make any difference. Problem #3 just came up, I tried loading different firmware back into arduro but it either gives me an error message or just says its loading the sketch and never finishes. Was wondering if the ramps is bad. One more thing that I tried was moving the heated bed wires over to the fan connection to see if it would work and it did, it heated up to about 55 degrees and stopped. So at least I know the heated bed is wired right. Sorry for the novel, but getting very frustrated cause I have had the printer since february and haven't printed anything and I have a list of stuff to print.
Thanks for anyones help

Quote
Shepp
next thing is I bought the full graphics controller with the sd card slotand plugged it in. All I get out of that is a blue screen, if I flip the connectors it screams at me with a different colour screen. I have changed settings in marlin but it didn't make any difference.

The Folger supplied software/firmware is a subset of the Marlin software/firmware and doesn't support the Full Graphics card. See this FAQ page..

Quote
Ecky

Quote
Shepp
next thing is I bought the full graphics controller with the sd card slotand plugged it in. All I get out of that is a blue screen, if I flip the connectors it screams at me with a different colour screen. I have changed settings in marlin but it didn't make any difference.

The Folger supplied software/firmware is a subset of the Marlin software/firmware and doesn't support the Full Graphics card. See this FAQ page..

When I got my Kossel a couple of months back, Folger's firmware ran the 128x64 graphic LCD fine. Maybe they link something different on the Prusa . . .

- Tim

Sorry, just quoting their webpage and recounting my personal experience. It worked with a version of Marlin I got from GITHUB but I didn't try to print with that version.

What can I say? Apparently thier Kossel can't read, since it does not appear to know that it is exceeding it's documented capabilities . . .

- Tim

It can but doesn't read the Prusa FAQ which is what this thread is about.

Regarding lcd blue screen, have you tried adjusting the contrast at the back of the screen?

An update, I tried with the contrast on the lcd and it didn't do anything. As far as everything else I am getting a new arduino and ramps cause I think I got a bad one.

I have a similar problem. My Heat bed will not heat up and the heat bed thermister reads Zero C which is impossible (should at least be room temp).
The resistence of the Heatbed is 1.8 Ohms and that of the thermister is 95K (both within working range).
Also, The voltage at the Ramps Blue socket where the wires to the Heat bed are connected read 0 volts.
It seems that either the Ramps board is damaged or that the Repetier host software is either faulty or not configured properly
Any advice?