HOTWIRE POWER SUPPLY

I wanted a DC power supply to drive my hotwire saw so that I don’t fry myself while cutting foam cores. I found some instructions online on these two sites:

• Converting an ATX Power Supply. A similar article can be found here.
• Alternatives to converting PC Power Supplies.

I selected “Converting an ATX Power Supply” as the recipe for building my power supply. I added a switch on the top of the power supply to switch between 6v and 12v. I also added a potentiometer so that I can control the heat of the wire. Well, that is where I spent most of my time. I am not exactly electronically gifted, so there was a lot of trial and error.

Rheostats and Potentiometers are fairly expensive items when it comes to handling the wattage required for the job. I bought a cheaper pot and used it as a rheostat. It could handle something in the region of 5 Watts. The first time I switched it on, I blew the smoke out of it. Then I tried a 250 W potentiometer that is found in light dimmers. That just did not work.

Finally I unhooked the potentiometer altogether (per advice from the Canard e-mail distribution list) and wired directly from the switch to the red post. It works great.

I tested it on a short piece of Nichrome wire. It got really hot on 6v and actually set the wood on fire when I switched it to 12v.

However, when I tested it with a longer hotwire bow, it would only work on 12v. The wire got hot (not red hot) and cut the foam fairly easily. Since I don’t have experience with other hotwire saws, I am not sure whether this would be sufficient or not. I think I would be fine for the canard. The wings might need a more powerful power supply.

	This is a picture of the open power supply, just as the instructions told me to put it together
	Another view of the insides of the power supply.
	The completed product. The knob on the front has been disconnected, so it is for ornamental purposes only now. I did not want to leave the hole in the front of it.