I had an idea for my hotwire set-up and tried this idea (see grotesque diagram). I used a 12-volt wall-wart (transformer), ran the negative wire to the cutting wire and the positive wire to a regular dimmer switch, then to the cutting wire. When I plugged it in…nothing happened- nothing.
Since I fear electrical repercussions, I thought I would ask people with more knowledge.
Thanks,
Damon
P.S. The small green wire coming from the side of the dimmer switch is the ground from the box that I left free.
While the diagram didn’t come through, let me hazard a guess anyhow:
Your typical wall wart transformer doesn’t tend to be especially high amperage: 1-1.5 amps and something on the order of 10-20 watts max if that. Plus whatever resistance is in the dimmer switch. You may want to go with a somewhat zippier transformer and that should give you more power delivered to the wire which should give you a nice cherry-red glow. Depending on the wire size of the nichrome wire you have in it: thinner wiire needs less power but it’ll cool faster during the cut which means you’ll have to run it through the foam slower.
The 6.3 V 3 A doorbell transformer I use ( with a 1’ nichrome wire, gauge not available just this minute 'cos I misplaced the spool it came on) works ok, though it’s a little light - I should go to lighter wire. I often get curved cuts due to the wire cooling as it’s melting foam.
First off, always ground your device, especially if you “fear electrical reprocussions”. You should also make sure that your device is fused, if it isn’t, put one on.
Second, remember that Current, EMF, and Resistance are intimately intertwined, a la Ohms Law. If you don’t know Ohms, you shouldn’t be messing with electricity.
Nicrome is high resistance wire, that’s the whole point, you want it to heat up. For a given length of nicrome you will have a set resistance. If you apply a fixed voltage to that resistance it requires a certain amount of current in order to complete that circuit. That amount of current is non-negotiable (see Ohms law). If the current required to complete the circuit is greater than the capacity of any of your elements (like your transformer) something breaks down. Remember that you are essentially creating a short circuit here, your only saving grace is the fact that the nicrome has more resistance than your average conductor. Replace that nicrome with copper and you would have a serious problem (don’t do this).
Personally I wouldn’t use the resistive/light dimmer approach to varying your input. You could just use a 555 timer and some transistors to regulate the pulse width, thereby controlling the amount of heat generated by the wire… but if you don’t know what a 555 is, maybe it’s best you stick with buying stuff. Go get a variable DC power source, capable of supplying 3-5 amps. That should work, but the gauge/grade of wire you use will matter significantly.