Do it yourself wire shielding.... advice?

[EWflyer]

I want to put some sort of shielding on a few short runs of wiring. I've been chasing my tail over resets that only happen when the laptop is connected to the processor. What would be the best material and/or method to use?

I know you might suggest that I remove the wiring I want to shield and replace it with specifically designed shielded wiring, but I don't want to go that in-depth just yet so I'm looking for some advice on shielding that I could just wrap around existing wiring to insure there's no signal interference between the laptop's inputs and the OPTO circuit wiring (which I feel is the most likely cause of the resets).

Thanks.

[Matt Cramer]

Opto circuit wiring seldom causes resets, but one good quick shielding method is to use aluminum foil tape.

['66fb]

Another method is to use the outer braided mesh you find on coaxial cable such as used for a CB radio antenna connection. Be sure to solder a short length of wire to one end of the braid to use as a "drain" wire and connect this to ground. insulate the braided wire mesh so it is only grounded at the point where you soldered the wire.

[msiddalingaiah]

Shielding might help, but you probably have a power and/or a grounding problem if this only happens when the laptop is connected. Make sure all of your power and ground lines are rated to handle the current and make sure all power ground connections are solid. I like to solder all connections, crimping doesn't do it for me. Also make sure you don't have a ground loop somewhere.

At one time I had left the opto inputs floating, which occasionally caused problems with my laptop. I grounded OPTO- to the frame (valve cover bolt to be exact) and I haven't see a problem since.

[EWflyer]

Well, I'm looking for solutions to my "Resets when laptop is connected" problem.....

Shielding might help, but you probably have a power and/or a grounding problem if this only happens when the laptop is connected.

I've been very careful to make sure all my grounds go to the main ground on the bike, a single bolt on the engine casing. And the power for the microsquirt is conditioned through a 30A rated, grounded, in-line capacitor-and-toroid combination. And I used large enough wire and everything is soldered. And I've tried several different laptop computers and several different serial adaptor cables.

At one time I had left the opto inputs floating, which occasionally caused problems with my laptop.

I'm not very experienced with electronics so I'm not sure what it means when you say "left the opto inputs floating." Does this statement mean that your project car uses the VR inputs and that you discovered the need to ground out the unused OPTO- line?

I grounded OPTO- to the frame (valve cover bolt to be exact) and I haven't see a problem since.

If you're using the OPTO inputs in a direct coil triggering setup what sort of resistor and zener combination did you use?

[msiddalingaiah]

I'm not very experienced with electronics so I'm not sure what it means when you say "left the opto inputs floating." Does this statement mean that your project car uses the VR inputs and that you discovered the need to ground out the unused OPTO- line?

If you're using the OPTO inputs in a direct coil triggering setup what sort of resistor and zener combination did you use?

I'm running MS-I on a motorcycle, so I only have the OPTO input for tach. Like most bikes, it has a CDI, which is a bit of a challenge since the coil input voltage is not well documented for all conditions. Instead of a direct connection to the ignition coil, I inductively coupled to it using about 12 turns of wire. There is an option in MS-I to not ground OPTO-, so I Ieft OPTO- ungrounded initially. It worked, but it would occasionally screw up the USB on my laptop. I don't remember if the computer ever completely reset, but it would hang quite regularly when the bike was running. After I grounded OPTO- close to the ignition coil, the problem went away.

What was happening in my case was probably capacitive coupling from the ignition coil all the way back to MS and the laptop. There are many tens of kilovolts on the business end of the coil, so even if a small fraction of that got back to the laptop, it is well beyond what most laptops can take. My tach scheme works, but I'm not sure I would recommend it. There's a lot of hash coming from the ignition coil that requires a decent amount of conditioning to achieve good reliability. If it becomes a real problem, I plan to tap the pickup coil pulses from the stator. That's about 20V max and much cleaner.

What are you using for tach? If it's anything close to the ignition coil, it's likely some of the juice is finding it's way to your laptop and poking it with little remorse. What you might need is a grounded shield (e.g. aluminum foil) between your tach pickup and the ignition coil. It's hard to explain not knowing what your wiring looks like, but that's just a guess.

[trakkies]

I like to solder all connections, crimping doesn't do it for me. {snip]

Pretty well every terminal you'll find on a flexible wire is crimped - not soldered. One reason being the wire can break just after the solder joint if there is any moment of the flex through vibration, etc. Unless it is mechanically supported after that joint, and the clamp on most terminals is too close to do this adequately. And of course that needs crimping. Crimping is the best way - but only with the correct crimp tool.