PWM Controller using 555 timer circuit (07/07/2010)

The net is filled with all sorts of PWM circuits that you can build which range from easy to complicated. I tried two circuits (with lots of aggrevation and burnt out 555 timers), this one worked for me..... So I pulled out the soldering iron, Vera board and bought all the components and started with the build. Components were cheap - where can you buy stuff that cost a few cents these days?

PWM uses a 555 timer IC (Integrated Chip) to create a voltage pulse over a range of frequencies. The circuit uses a potentiometer to control the frequency of voltage pulses from 0-100% of the designed frequency. The operating frequency of my circuit is 144 Hz. PWM works well on hot wire cutters as it pulses the voltage on the wire rather then having a full voltage (I am using 12V) applied to the wire which will just result in the wire going up in smoke!!!! I experimented with wire I could easily get hold of and scavenged off the silver braided shielding used on coms wire for PLC's - abundance of this stuff where I work!!!!

But to give you an idea this is what I measure - 0.25mm dia, I use 300mm long with a total resistance of 1ohm.

I used an IRF540N MOSFET instead of the one on the circuit - coz I had one. I also built in some protection (after learning the hard way). There is a 2.5A fuse from the +V to the hot wire (the hot wire fits in between the "M1 DC Motor") and I have included a BIG diode ± 3A rating for polarity protection on the supply side. All this to protect the 555 timer from 'that nasty burnt silicon chip smell"...

Update (12/10/2010)

The PWM control box has been used on a 12 V blower I acquired for the forced air supply to my HOTPOT furnace. IT WORKS PERFECTLY!!!! i will also use this for the spindle control on my CNC machine....