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How hot do your solenoids get? With Video
WindDrake:
Just thought of something else.
How are you triggering the coil?
First thing that comes to mind is using a P-Channel Enh. FET and using an active-low signal to trigger it, with something 4.7k or so as a Pullup resistor to the rail.
There is a possibility that you've got a transistor that isn't turning all the way off. Coils, like any inductor, are going to try to resist changes in voltage, so I can't see a pulse width being a problem unless it's super, super long.
I'd check and see if you've got a leak. Either a partially biased fet, or a leaking anti-ringing cap, or even a bad flyback diode.
charlieram:
See, its stuff like that I just dont know, Well over my head. mame hooker is sending an 18ms pulse to the coil, well that is what i can ask it to do minimum, any less than that and it doesnt activate consistently. I have no way of checking how long the voltage is supplied to yh coil or whether it is on/off or rising and falling. this is why i would like advice one my circuit. DaOldman has been really helpful but he doesnt have recoil guns.
Fursphere:
So.. I've had solenoid pump black smoke out of my pinball machines. If I wasn't present I'm curious if it would have caught fire.
lilshawn:
--- Quote from: charlieram on August 22, 2013, 04:36:51 pm ---I have no way of checking how long the voltage is supplied to yh coil or whether it is on/off or rising and falling.
--- End quote ---
fire off your solenoid a few times... use voltmeter to check your + and - on the solenoid after. if there is a residual voltage left flowing after it's been fired off, your FET isn't turning off all the way causing a tiny flow. you may need to use a pull down resistor on the FET to get it to shut all the way off.
you may find when you fire it off a couple dozen times the voltage is going to build up and up and up and stay for longer until it bleeds off naturally through the coil. (could be several seconds) that would be where your heat is coming from.
but, if it dumps right back to zero, it's not bleeding voltage.. you may just need to shorten your pulse length.
ideally you want the pulse to be just as long as it takes for the solenoid to go from it's normal resting state to fully retracted. if it takes 8 MS to do that, there would be no sense driving it any longer than that. It's pretty difficult to measure that, I only mention it because it pertains to this situation.
--- Quote from: Fursphere on August 22, 2013, 07:14:21 pm ---So.. I've had solenoid pump black smoke out of my pinball machines. If I wasn't present I'm curious if it would have caught fire.
--- End quote ---
a stock system, no. It will melt and smell nasty but it shouldn't catch fire.
on a rigged system (IE over fused) yes, it's very much a possibility. not to mention you risk burning a hole clean through your driver board as the FET burns up and takes out ALL your wiring with it.
lesson kids: if it says 3 amp fuse. IT'S A 3 AMP FUSE ONLY! not a 4 amp, not a 10 amp, not a 30 amp, and ESPECIALLY not tinfoil. :angry:
charlieram:
--- Quote from: lilshawn on August 22, 2013, 09:03:12 pm ---
--- Quote from: charlieram on August 22, 2013, 04:36:51 pm ---I have no way of checking how long the voltage is supplied to yh coil or whether it is on/off or rising and falling.
--- End quote ---
fire off your solenoid a few times... use voltmeter to check your + and - on the solenoid after.
--- End quote ---
I had actually tried that but my voltmeter isn't very responsive, It is a digital one I bought years ago for some project and then I didn't use it for years. It takes too long for it to register voltage before the solenoid has fired and then gone back to rest. If I use the fully automatic gun on T2 it catches the high voltage eventually but not the low. I also checked the voltage across the coils when no output is required and that seems OK (0v)
My circuit is below
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