Monday, 15 April 2013

Hot Wire Polystyrene Cutter–Part 3

I’ve been doing some tinkering and going through old AC Adaptors to see what I had hanging around (mostly from old mobile phone chargers).

I connected a 9V adaptor to the styrene cutter and I still didn’t get enough current through to heat the Nichrome wire. It seems that my wire is too long to be able to generate enough resistance in a short enough space to produce the heat that I need to cut the polystyrene.

I have a couple of options:

  1. Reduce the length of the Nichrome wire. This isn’t a particularly attractive option as it means that I have to do some structural remodelling of the table and arm;
  2. Reduce the gauge of the Nichrome wire. This option doesn’t seem practical as I have pretty much exhausted my supply here in Hobart. I could harvest some Nichrome wire from an old soldering iron (that’s what’s used to heat the iron) … this is possible, but I’ll use this as a fall-back option; and
  3. Increase the voltage of the adaptor that I’m using. This is probably the best next step in the design evolution of the polystyrene cutter.

I tried connecting my 12V car battery charger to the cutter to see if increasing the voltage to 12V would have the desired effect. The cutter certainly made some clean cuts, but the internal fuse in the recharger kept on tripping, so I can’t really use that in the long term.

Cleaning out some old electronic equipment, I found a 12V adaptor that used to power a TV antenna (with boost/gain). The antenna is now obsolete since analogue TV has now been phased out. The adaptor is 12V 600ma, so that should deliver the power that I need.

I will probably also need to remove the 5V fuse from the circuit … I’d also like to put in a light (such as a LED) so that I can see when the power is on. At the moment, the toggle switch doesn’t give any indication that the power is on … so I am also guessing when the circuit is actually live.

I’ve made power connection a little bit easier for myself by including a screw terminal block.

Changing the power should be a fairly quick operation, I just need to cut the connector from the end of the adaptor cable, tin the wire and then connect the cable ends to the screw terminal block. Fixing in the LED is going to be a little bit harder … but not too hard.

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