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Old Oct 10, 2012, 04:32 PM
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United States, MO, Fenton
Joined Jul 2012
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Novice trying to build a hot wire foam cutter

Hi, all,

I am planning to build a hot wire foam cutter. I have to confess that I am not very confidence with my understanding of electricity (besides turning on and off the light switch... ). After reading through and following the threads, I am still a bit confused as to how best to proceed.

I have a power supply that I use to run my LiPo battery charger (Thunder T610). It is printed on the power supply "12 volt, 20 amp". I know that this power supply outputs DC power. There is a LED screen on the power supply indicating the amperage. When I run my battery charger, the amperage would show a certain number and then starts to drop as battery charging is near completion. So, my understanding of this power supply is that it outputs a maximum of 12 volts, but the battery charger asks for a decreasing amount of voltage as time goes by, hence a drop in the amperage (V=IR, resistance is constant in this case).

So, I would like to be able to use this power supply as my power source for the foam cutter. I have not decided on the materials of the wire yet. I was thinking of using a guitar string as I have them lying around. Or, use carbon steel welding wires. The length of cutting wire probably less than 1 meter (3 feet). However I am concerned about electrocuting myself (with the 20 amp electricity). My questions are:

1) Is this power supply safe to use?

2) My understanding is that, without any voltage regulation, the power supply will put out 12 volts constantly. So, if I were to vary the length of the wire or distance between the two alligator clips (changing the resistance), I can get different amount of current going through the wire. Therefore, finding an optimal heat level. Is that correct?

3) If the power supply heats up the wire too much and, instead of changing the diameter or length of the wire (increasing R), I would like to regulate the voltage going into the wire, could I put a potentiometer in between the power supply and the cutting wire? If so, what kind of specs on the potentiometer should I be looking for?

Thanks for your input and suggestions!!
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