controlling a hotwire

**cncmachineguy** · - 27th January 2011, 02:04

I know there are plenty of circuits on the net for this, but I have not found 1 to make me happy yet. Heres the set-up:

My wire is 19 ohms. This is measured not calculated.
My goal is around 50W. I think I remember this from earlier testing of a shorter wire.
Trying to avoid a transformer.

I want to control the heat (crudly no precision needed here) using a PIC. I am looking for the least expensive way. BTW without the PIC requirment a light dimmer would be just fine.

Now WAY back in collage, I recall a SCR switching circuit to control the avarage voltage across a motor for a simple speed control. Thats about all I remember from it.

Any thoughts on how I can accomplish this? Of course I can find SCR circuits, but maybe there is a better choice now days? It doesn't have to be clean the wire will avarage the heat so DC is not needed.

My reason for wanting to run direct from 120 is if I can raise the heat to 75W or so, I can clean (burn off the foam) the wire between cuts.

EDIT: Just dawned on me the question could/should be simply "How to control a 100W light bulb with a PIC?"

**mackrackit** · - 27th January 2011, 02:45

http://www.picbasic.co.uk/forum/showthread.php?t=1026

http://melabs.com/resources/samples-user-file.htm
Dimmer zip

**cncmachineguy** · - 27th January 2011, 02:55

Thanks Dave, Can't seem to get the app note to load, but very good info!!

If you can edit, I can too

thanks for the melabs link. Maybe I should go and read through the stuff there sometime.

This seems exactly what I need!

**mackrackit** · - 27th January 2011, 02:59

This one?
http://ww1.microchip.com/downloads/e...tes/40171a.pdf
Loads here, I could email it to you...

**cncmachineguy** · - 27th January 2011, 03:23

Must have need you to get it jumpstarted. Any ideas for the TRIAC? looking for the one listed in the app note now, no joy at digikey. No part number on Mister_e (tm) circuit.