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Old Jul 03, 2005, 09:27 PM
irwinrc is offline
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Can't cut a straight line
Somerville, NJ
Joined Jun 2005
9 Posts
first week in rc planes nd I''m already playing with cdrom - uggghhh

Originally Posted by Bruce Abbott
It is possible to use a non pre-driver IC with external FETs. Connect a resistor from each motor phase to the supply, and another to ground. Then you can detect three voltage levels using two comparators, one per output FET. This requires 6 comparators and lots of resistors, so is probably more complex than using a pre-driver IC.

I chose the NJM2624 pre-driver for it's simplicity, availability and low cost (just $0.90 each at Mouser Electronics). One thing to watch with this chip is that although it can work down to 4.5V, its outputs can only go up to 1.5V below the supply voltage. Therefore at least a 6V supply may be needed to drive logic-level MOSFETs.

My circuit makes a stock CDROM motor act like a brushed DC motor, which can then be driven by a normal brushed ESC. The breadboard prototype worked very well, so I am now working on a surface mount version. The output switches will be SI4542DY dual N&P MOSFETs, for a total of only 24 parts on the PCB.
I'm trying this out, built the circuit up on a breadboard with huge mosfets

I just finished figuring out the pinout of the cdrom motor I'm going to use, came out of a busted acer cd-rw drive. Wish me luck soldering little wires onto the edge card connector -- haha.

If I can get it to work with stock windings then I'll rewind it with some of that thicker magnet wire I have laying around, and see what 18 turns does to it

This is my first week on egroups and look at what I am doing -- next I'll be building planes out of blucore to put the motor in
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