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Megasquirt Quick Wire gauge question for CAS signals

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Old 12-15-06, 12:07 PM
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Quick Wire gauge question for CAS signals

I can't figure out what gauge wire to use for carrying the CAS signals to my LM1815 circuit in the proto area of the board. I'm running a completely stock ignition on an S4. I'm planning on ordering shielded wire from this site:

http://www.aircraftspruce.com/catalo...shieldwire.php

Sorry for the stupid question, but thanks for any help.

-Andrew
Old 12-15-06, 12:27 PM
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iirc I used 18 gauge (just what I had laying around).
Old 12-15-06, 03:18 PM
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I don't think it matters what guage you use... mine was 20 ga wire in a twisted pair configuration inside a shielded cable.
Old 12-15-06, 04:13 PM
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Do you think that the wire I linked above would give me issues because its not twisted pair? And if I need twisted pair do I hook up both wires to the same signal? Thanks for the help.

-Andrew
Old 12-15-06, 04:13 PM
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I think mine was 16 ga. because I had a bunch of it around. I also custom made my shielding using a coaxial cable.
Old 12-15-06, 08:03 PM
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I don't think you'll necessarily have issues if it's not twisted pair, but twisted pair is better.
Old 12-16-06, 12:11 AM
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Alright, good to know, thanks for the help. Just one last question, do I hook up both wires in a pair to the same signal? Or do I hook up one of the wires to the G+ and its pair to the G-, and the other pair run the Ne+ and Ne- signals? Thanks again, I just want to make sure I get this right before I put everything together.

-Andrew
Old 12-18-06, 08:43 PM
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Not sure about what gauge but I used thin speaker wire.

If you want to know how to do a good shielded wire, which removed my noise problems.

OK,

For the CAS each wheel output has 2 wires, the positive and the negative. The negative wire is actually the ground wire and the +ve wire is the signal wire.

A good method is twisting the +ve and negative wires, the -ve wire is the ground wire, so this provides some grounding.

The next thing to do is to shield the twisted pair, using tin(Aluminuim, the stuff you use for wrapping up fish in the oven) foil and adhesive electrical tape, form a metal shield for the CAS wire from the engine bay, to inside the cabin where the ECU sits. Make sure the metal shielding is not grounded in the engine bay, and short the foil to the same pin that the -ve wire from the CAS pair goto. Use a paper clip to join the shield to a wire. Non soldered connections will be more reliable.

Before covering your new shield in electrical tape make sure you test for continuity from one end of the shield to the other, a good connection is required for the shield to work!

The shielding is much more important than the gauge of the wire in this case!
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