Build Your Own Arcade Controls Forum
Main => Main Forum => Topic started by: 1UP on March 14, 2010, 07:58:56 pm
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I'm trying to get my Happ recoil gun rig all cleaned up for actual use (vs testing), and the final step involves running a USB connection for the Aimtrak board down thru the same hose that houses the +24V for the gun's recoil solenoids. Since there are 4 wires available from the existing harness now that I've removed the gun's original optics board, I thought the easiest way to do this is by just splicing USB connectors onto each end of the existing wires, as there is not really enough room in the hose to fit a full, shielded USB cable.
The question: is there any danger that the nearby 24V current through that tight conduit, or any resulting EMF from the solenoid, could fry my Aimtrack, or worse, the PC that the USB is connected to? I'm not as worried about the board being fried/interfered with directly, since it is a good 6-7 inches from the solenoid, and the old optic board was only 1-2 inches away from it. Just wondering about crosstalk through the wires thin insulation.
Thanks :)
Rob
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Personally (no technical reason) I would er on the side of caution and probably just run the USB cable down the outside of the hose, maybe slip a new hose over the top, May not look as nice but safer over all
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The solenoid itself may have some pretty nice magnetic fields associated with it (that's how they work, after all), but the lines driving it shouldn't be too bad as the loop area is small. USB cables are also shielded pretty well. I wouldn't worry about it. USB ports and devices are usually pretty hardy. Even if EMI does cause interference (which I wouldn't expect), I can't imagine anything would be damaged.
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USB cables are also shielded pretty well. I wouldn't worry about it. USB ports and devices are usually pretty hardy. Even if EMI does cause interference (which I wouldn't expect), I can't imagine anything would be damaged.
The OP did mention that he intended to splice USB cable onto the original data lines from the harness.
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Oh, don't do that. That may not even work at all for full-speed USB (though low-speed will probably still work as it's pretty forgiving). The transmission line characteristics will be all wrong, and the lines won't be twisted which kills the differential coupling. I still wouldn't expect damage from EMI, though.
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Thanks for the info. Hmm, maybe I'll just have to see if Mouser has any USB 2.0 cabling with a small diameter. I'm not actually sure if the whole hose is this way, but the metal anchor on the end of the cable is only about 1/8" wide. May be possible to just bore that to a larger size, though it might prove difficult on my drill press...
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Oh, don't do that. That may not even work at all for full-speed USB (though low-speed will probably still work as it's pretty forgiving). The transmission line characteristics will be all wrong, and the lines won't be twisted which kills the differential coupling. I still wouldn't expect damage from EMI, though.
Agreed.
Note that you need to connect a diode across the coil to prevent large back-EMF spikes from being produced when it de-energises. Otherwise i would expect USB will be affected but not actually damaged.
Andy