Dimmable Halogen Lamp Transformer for Hotbed power supply?

I made myself a hotbed with 28 gauge nichrome wire, i wanted bigger than 26, but i forgot i should've ordered 24 for that... I'm a bit worried about the size of the wire.

I thought i could try powering it with the 5v rail of my power supply but, when i wired the thing i made an error thinking i was going to get 10 times 5W. But the way i wired it, i'm getting the equivalent of 12" of 22 gauge wire, about 1 Ohm(measured). So with a theorical 140W at 12V, i should be able to avoid the red burning wire of death...

So i was looking at a solution since i already have a old pc power supply i can use. It works fine for the electronics and motors but its not powerful enough to power the bed, even alone the overpower protection kicks in and it shut's down. Turns out, that "450W" power supply i wanted to use, the transformer inside is only rated for 130W... Meh..

If i focus on what i'm missing, power for the bed, i dont need DC... 12V AC should be fine, the nichrome wire will not see the difference...

Looking through the power supply available on ebay and aliexpress, i found a Dimmable Halogen Lamp Electronic Transformer. [www.aliexpress.com]

I was thinking i could use a Digital POT IC instead of the analog POT they provide and hook it up to the ramps with some voodoo arduino magic i could vary the voltage to the bed instead of the usual on and off. And that way i can go easier on the nichrome wire.

The alternative of course would be to buy a 300W-400W 12V only power supply and use a relay or something connected to the ramps. Not sure of what's the best thing to do.

Edited 2 time(s). Last edit at 01/18/2014 11:30PM by swe3tdave.