AVR driving solenoids

Nov 17, 2006 5 Replies
A

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


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R

[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

Ing.Buero R.Tschaggelar - http://www.ibrtses.com & commercial newsgroups - http://www.talkto.net
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M

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

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A

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

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A

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.

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A

Arlet wrote in sci.electronics.design:

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

Anno

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