No voltage to heated bed with Marlin

Hi I am having issues with getting the heated bed to work for an i2 build.

The bed in question is a custom build consisting of two power resistors and an LED in series. The issue seems to be software related as connecting an external power source to the bed runs it fine. I am running Marlin 1.0.0 Beta 1.

I thought I could hook it up to the arduino in the same manner as the hotend's resistor but after following the wiring [reprap.org], although my heated bed thermistor shows up in Pronterface fine, when I click 'set' to raise the bed temperature, no voltage is sent to the bed.

Any help would be appreciated on getting this to work.

Configuration.h:
[pastebin.com]

It doesn't sound like a software issue to me. It sounds like an issue with your controller board - either a faulty component, or a bad or missing solder joint. What are you using for your controller? And did it come pre-assembled or did you solder it yourself?

I'm using RAMPS 1.4 attached to Arduino Mega 2560, it came pre-assembled. How can I test for a fault?

I actually think its my pins.h that is wrong.

[pastebin.com]

Any ideas?

Edited 1 time(s). Last edit at 01/18/2013 10:11PM by coresnake.

Hmm after reading some help for a different machine the person was advised that the D8 pin merely ran a small voltage to turn on a mosfet which ran the heated bed, implying an external power source was needed to run the power for the bed. Is this true for the Prusa i2?

Yes that's true, but its all managed by the ramps. The ramps has two power rails and you should be making two separate connections from your power supply. I'm not sure which rail is used for what, but the power supply connected to the ramps should provide power to your bed. What power supply are you using?

That could be the problem, I'm only hooked up to the 5A port from my PSU, as I was told previously that I only needed both power rails if I used the device in standalone mode (not hooked up to US. Do I need both power supplies for the heated bed?

I'm not sure what is powered from which rail, but I know the heated bed is powered from the larger of the 2. SO if you're only applying power to the 5 amp rail, there's your problem. The heated bed, with its small resistance, draws a lot of power, anywhere on the order of 10-12 amps.

Ok thanks I'll try it