Will this work Motor controller with PNP NJW1302 250v 20A BJT

188

02:01:12

450 mA planned on base of final stage to produce 4.5 at 90v being controlled by arduino amplified with a simple PNP - npn- PNP design scheme

published 3 years ago

mlira

3 years ago

If you're looking at high currents controlled by an Arduino I'd recommend a MOSFET over a BJT. There normally cheaper for high currents and have negligible gate current so you can attach them straight to the Arduino (just remember the pull up/down resistor). A IRFP250 would probably meet your needs.

drkblader12

3 years ago

By pull up resistor do you mean to pull the ground up? Similar to the Cathode of a vacuum tube?

drkblader12

3 years ago

I already have lots of these NJW1302’s and have already lost money trying to fix my 90v 1/2 HP B-DC motor so I’m just trying to get by with simple controls to save the 100$ for a new controller.

mlira

3 years ago

The pull down resistor on an N channel MOSFET is to provide a path to ground and lower the gate voltage (P channel has a pull up resistor to do the reverse). As MOSFETs have negligible current flowing through the gate they act a bit like capacitors and the gate voltage will stay high when the signal is switched off, so the pull down resistor effectively just discharges the gate when no voltage is applied.

mlira

3 years ago

If you forget it then the MOSFET just stays on and you wonder why your controller isn't working. (I've done this many times)

mlira

3 years ago

If you want to use the BJTs you have then I would probably start with something like the right side of https://everycircuit.com/circuit/4756063162990592 but I'm not sure what the resistors should be and will depend on whatever NPN transistors you have.

faceblast

3 years ago

need more gain on the output stage. NJW1302 should be doable but run them as low side drive common collector because of their low hfe, maybe a couple of them in parallel

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