Hello,
I have a PWM driver that I got from the makerbot store along with my generation 2 electronics. When I hook up the nicrome wire to it to see if it heats up, the ATX power supply shuts down before it heats up.

I have no clue whats happening.

Thanks,
Drummerboyx

sounds like you either have a short or are trying to pull more current through the PWM than your power supply can handle.

_________________________
[reprapetc.blogspot.com]
^^I plan on updating this when I have time. For now there's not much there.

Or you are missing a dummy load on the 5V rail.

[www.hydraraptor.blogspot.com]

What do you mean nophead?

Most PC PSUs do not work properly unless they have some load on the 5V and possibly the 3.3V rail. It is because the rails are not individually regulated. If you only load the 12V rail and leave the 5V rail unloaded it has to throttle back to prevent the 5V rail being over voltage. That leaves the 12V rail under voltage, typically about 10V.

I haven't seen one shutdown but it is conceivable that it may. If you follow the RepRap instructions they recommend adding a dummy load resistor to the 5V rail.

[www.hydraraptor.blogspot.com]

I looked at the reprap ATX instructions and I couldn't find anything on it. Can you tell me or give me a link to the instructions?

thanks,
drummerboyx

[reprap.org]

I think the gen3 motherboard has a site for the load resistor.

[www.hydraraptor.blogspot.com]

Yes there is a site for a load resistor...

I have at least 5 diffrent ATX power supplies in use for powering various combinations of reprap boards. I still have not needed any kind of load resistor to maintain the ATX power.

~(I owned a computer shop form 1988-1998)~
The simplest load I would use for testing the voltage of any PC or ATX PSU would be any old hard drive or CD, DVD drive easily avalible with no need for special power resistors that could be a puddy burning hazard if forgoten about.

This could also be because I usualy have 3 motor controllers connected and an Arduino board.

I test newly built boards one at a time without any power problems thou.

The Older PC and Atari ST switch mode power supplies that had insuficent load would tend to motor boat the supply (rapid surging of the supply voltage up and down modern ATX supplies do not do this).

The bigest enemy of all Switch mode Power Supplys is your central heating pump and thermostat. The will produce nasty high voltage spikes on your mains supply just like a car ignition coil. So always have an anti-surge plug to power your PC supplies this removes any high voltage spikes. This is possibly not such a big problem in the USA.

Bodge It
=======================================
My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]

Funny I have yet to find a PC power supply that gives the correct voltage on the 12V rail with nothing on the other rails.

[www.hydraraptor.blogspot.com]

I test newly built boards one at a time using a Sanguino or Arduino processor that uses the 5V supply as I remove the power selector link. Ie not powerd by USB or 12V

I have to use a Sanguino or Arduino processor board to test new PCBs as new PC's do not have a printer port to provide control signals to test the boards.

Bodge It
=======================================
My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]