Foam cutting hot wire regulator

Discussion in 'The Projects Forum' started by amateurb0y, Sep 8, 2013.

  1. amateurb0y

    Thread Starter New Member

    Sep 8, 2013
    Hi folks, new member here who needs a dead simple potentiometer-controlled circuit for hot wire to cut polystyrene foam.

    My DIY standard cutting bow is about 30" in wire length. I'm using a 2 cell lipo for the power source (nominal 7.4v), and it works quite well. However, I need fine control of the volts/amperage to get a really smooth cut. I'm using nichrome wire 0.4mm/27 swg which has a nominal 8.6 ohms/mtr resistance(?).

    It would also be really handy to be able to make much smaller cutting tools using much shorter lengths of stronger wire, say 0.6mm(?) for smaller cutting jobs if the same pot will handle it..?

    I need to have fine control in the, say 7.5v to 8.5v range. It's important to keep the amperage in a tight range of approx. 0.8 - 1.3 amp(?). to get a nice smooth, slow cut. So a pot capable of handling say, 12w max. is needed.

    I've seen a hobbyist on Youtube who uses an R/C servo controller and a brushed motor ESC (difficult to get nowadays) to achieve fine control, but I can't quite see how he's got it wired in to the circuit!

    Can anyone point to me to a potentiometer with whatever product code/spec. I need, please?
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    Why don't u buy a buck converter from ebay with current limiting capability like this one
    They are cheap and quite good. Better than building a linear one. Waste less energy as heat and are replaceable quite easily.
    U can have strict control over current or voltage. Which ever u need at the time. Plus a display is quite handy.
  3. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    A potentiometer that will handle the power required for a hot wire cutter either is prohibitively expensive, called a rheostat, or really not what you need.
    You want the pot to control a circuit to pulse the power to the hot wire or control the power to the transformer with a variable transformer (against tos though).
  4. amateurb0y

    Thread Starter New Member

    Sep 8, 2013
    Thanks, that clever device sounds ideal. The one you linked to was actually from China, and stuff from China takes a long while to arrive, but I found a very similar device on eBay UK which just has the one adjustable pot. It should do the business for me anyhow.

    Many thanks for that tip...