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Topic: quick driver current question (Read 721 times) previous topic - next topic

Docedison

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"The solution of every problem is another problem." -Johann Wolfgang von Goethe
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herewego

Thanks. I was hoping i could avoid ordering stuff though. Also I don't think that shield solves the problem of not supplying 2.8 Amps to the motor. So the transistor idea is a no go?

Magician

Quote
DESIGN 19
High Current H-Bridge-2
This circuit will deliver up to 3 amps to a 6v motor. Use TIP100 (NPN) and TIP105 (PNP) for 8 amp
H-Bridge.

http://www.talkingelectronics.com/projects/H-Bridge/H-Bridge-1.html

Docedison

Design 20 will work as well and it can also be PWM'd... The BC547's are 2N222A's. Actually after having re-read the data sheets on both I'd use the 2N2222A's. One other point re: design 19... 1N4148's are TOTALLY inappropriate as back emf diodes, Use 1N5404 3A 400V PIV diodes...

Doc
--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

oric_dan

The problem with those sorts of circuits is, they are firecrackers waiting to go
off. If both high and low sides of the bridge get turned on simultaneously for
any reason, you get smoke. Eg, error hooking up. Eg, error when using scope
probe. Eg, one of the other transistors shorts out for some reason, eg,
inductive spike.

I would use a fuse in the battery line.

In my own playing around with h-bridge prototypes, I once literally set a 754410
chip "on fire". I'd seen smoke before, but never actually "fire". LOL. In another
case, the top MOSFET didn't shut off properly, so there was a short through to
the lower MOSFET, and IIRC, they both melted off the pcb, after the smoke.
8 Amp designs are really dealing with quite a bit of current, and low pathway
resistances.


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