Monday, 22 April 2013

Hot Wire Polystyrene Cutter–Part 4

Finally! I got the time to install the 12V AC Adaptor into the polystyrene cutter.

I also put in a 5mm red LED and a 470 Ω resistor between the switch and the NiChrome wire. I did this because my switch doesn’t really tell me when the device is on. I simply soldered the Anode leg of the LED to the switch, the resistor to the cathode leg and a short length of wire between the resistor and the cutter “head”.

I cut the adaptor coupler off the end of the adaptor wire, stripped and tinned the wire and connected it to the terminal block.

Using a ready made power adaptor makes this a very simple circuit.

Polystyrene Cutter_schem

A possible enhancement would be to add a 10K pot between the resistor and the NiChrome wire.

I powered the cutter up and, presto, the NiChrome wire got good and hot. Hot enough to cut through the polystyrene with very little resistance. The polystyrene leaves some residue on the wire, but this can be picked off without any trouble.

I will make a smaller, hand-held version of the polystyrene cutter using a 9V battery as the power supply. The main reasons for making a smaller version are:

  1. I can use the smaller pieces of NiChrome wire when it breaks (and it does break, so be prepared for it);
  2. A hand held cutter can be useful for smaller more complex cuts.

The way that this works is fairly simple. The NiChrome wire acts as a resistor, the energy has nowhere else to go in the circuit so it is converted into heat … the end. I am bleeding off a tiny amount of electrical energy with the LED, but it is a trivial amount overall.

My youngest thinks that the cutter is cool and wanted to cut some shapes using it, she had no trouble after I gave her instruction. Then I got to explain the physics of the project … she thought that bit was boring (hahaha)

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