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Need Advice on Pulse Width Modulator

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snub:
Thanks for the advice, gentlemen. Not sure if there is a diode in the circuit. There is a component marked 'D4', which I suppose could be one. Here are some better pics:

Bluechip:
Snub

Yes, that's a diode. Looks like it may be either a 1N5408 or a UF5408 ..

At least on my pic it looks like an '8' for the last digit.

1000V Vrrm 3A. Good enough .. if it is one.

If you look at the traces under the circuit board, it should be effectively wired across the output terminals, cathode [ end with the bar ] to the positive motor terminal.

In fact, as it has 2 signal diodes and a few other bits, you may well find the contraption is based on the generic 555 Timer Chip PWM schematic.

Similar to this one  ... maybe not exactly,  but ...

http://www.discovercircuits.com/DJ-Circuits/simplepwm2.htm

It is a common practice to parallel off two [ or more ] MOSFETs to get more grunt .. which may be what you have..







BC

John Swift:

Hi Snub ,

just to add to Bluechips reply

if the board is designed to work on more than 18V

I expect you will have a voltage regulator to supply the NE555 timer , on one heat sink
and a FET to control your motor on the other

       John

Bluechip:
Very good point that, John...

Never occurred  to me  :scratch:

Which probably explains my habit of re-inventing the Direct Arc Furnace ...  :bang:  :bang:

 :lol:

BC

snub:
Thanks, again. The vendor states that this unit will work on 12-24-36 volts. I'll take a look and see how the diode is wired in.

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