Actually, thinking about it, even though the solenoids are rated 27V doesn't that mean it takes 27V to trigger them? So 30V is probably safe for them. All you are doing is powering up a coil of wire to make an electromagnet. I know someone recently asked me if a resiter is needed to knock 30V down to 27V. This isn't a LED that will burn out quicker, just an electromagnet.
Level42, I like that design. If you find the right parts I would probably go with that. It would be a fast mechanism to.
Well, first: the 3 Volts more or less won't matter much. The coil is getting a very short pulse only. I bet it never actualy reaches the full 30/27 Volts but at those ratings 3 Volts doesn't really matter much, and indeed it's a coil getting the voltage, nothing very delicate. No need for resistors.
Indeed, this will be a lot faster then a relay, my feeling is a relay won't work because of the short pulse.
This is what Brad says in his e-mail to me:
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The triggering needs to last a mere fraction of a second. A half second is
wayyyyy too long. In my Q*MAME code, it is turning on the LED and turning
off without any delay at all. It should be the least amount of time
possible. I didn't want to use a relay because I thought it would be more
likely that a relay could get stuck in the ON position, which would not be
good.
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Thanks, I do hope it works though

Gotta build it first but the 30 Volts on the Base of the darlington (through the optoisolator) worries me a bit. I think it'll need a resisitor there.