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AVR driving solenoids

For a one-off project I'd like to switch about 30 solenoids (12 V, 1 A) with pulses between 20 and 50 ms duration (duty cycle < 10%) generated by an AVR processor.

One solution would be an optocoupler that is able to drive the load directly. This is attractive for its simplicity (I expect to hand-solder 30+ of the circuits) and the galvanic separation of the

12 V from the logic, though the latter would not be strictly necessary.

I have found one available part, PVG612 (data sheet at

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that does the job. The unattractive part is the price of 4-5 $ per unit in small quantities. Actually, the PVG612 does more than I want; it is more of an electronic relay (with AC capability which I don't need). On the other hand, the device has delays of 1-2 ms. That's acceptable and can be compensated but a tighter timing would be nice.

So I've been looking for alternatives but come up empty so far. Any tips?

Anno

Reply to
anno4000
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[snip]

You didn't look really far for alternatives. Since a solenoid doesn't need galvanic isolation, you could as well use bipolar NPNs or N-Mosfets

Rene

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Reply to
Rene Tschaggelar

use something cheaper like a 4N28 from fairchild to drive a biggish npn transistor. Dont forget to put a reversed biased diode across the solenoid

martin

Reply to
martin griffith

Right, that's where I was coming from. I had some problems with a BC141-16 in preliminary tests (probably due to too little beta). Also, the idea of keeping away the 12 V (or more) driving the solenoids from the logic and other equipment attached to that seems attractive, though also not strictly necessary. That's why I was looking into optocouplers in the first place. I'll be back to transistors when that doesn't pan out.

Anno

Reply to
anno4000

If you're worried about damage, you could take a look at the BTS711 part. It's a quad 1.9A high side switch. It can switch 12V inductive loads, controlled by uP, and has all kinds of protection circuitry, including short circuit and overvoltage.

Reply to
Arlet

Arlet wrote in sci.electronics.design:

Ah, thanks. That looks much like the kind of thing I was hoping for.

Anno

Reply to
anno4000

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