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Unread 17-02-2015, 10:57
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Re: Firing two solenoids together

Quote:
Originally Posted by rich2202 View Post
IMHO, the potential delay of the electrical system is dwarfed (on the time scale of electrical signal delay) by the tolerances of the mechanical system.

Even if both solenoids fired at the exactly the same time, there would be a difference in timing due to mechanical movement (opening/closing of the valve).

Similarly, even if you had it T'd off one solenoid that could instantaneously pressurize lines of the exact same length, there would be mechanical differences of the pistons themselves that would make one move faster than the other.
I would have thought the same thing. We were careful with our system, and added flow control valves so we could manually adjust the speeds of the two pistons to match, and they do, in fact, match. But we noticed on was starting up before the other. Programming switched the two lines of code, and we saw a corresponding change in the motion of the pistons. It's not much, and doesn't really affect how our system works, but it got me thinking.

Quote:
Originally Posted by cgmv123 View Post
R42 says one (pneumatic) solenoid (valve) per PCM channel.
Good catch. I swear, I spent 15 minutes looking for this rule this morning, but somehow couldn't find it. Turns out I was looking in the wrong sections... It's in power regulation, not controls or pneumatics!. I had even searched for "PCM", but the table spells it out instead of using the abbreviation like in other locations. I can't wait until Wednesday and the blessed Sleep it'll bring.

Anyways, the question still stands... How do we get 24V solenoids to trigger at exactly the same time?
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