using 24ga cat5 'network wiring' for the car being towed (2 power the magnetic rear lights)

since I have an "ocean" of the cat5 (computer network wiring, four or more 24ga conductors per sheath) stuff laying around here, and very little of other, bigger gauge wire, I'm thinking of wiring the towed car rear lights with cat5 from the towed vehicle. I realize 24ga is probably 'undersized' for a 'one wire per function' (brake/turn left, brake/turn right, running, and ground) deal, so I could double it up, and make it two conductors, or more, like 3 conductors, per function. they could 'share the load' :-). it'd all be soldered and insulated, taped, zip-tied correctly, of course.

I don't feel like romping out and buying, like 20 or 25 feet of four conductor 'heavy gauge' stuff for a 'one time use' situation. also have a pretty fair amout of, i think, 14ga three conductor romex...

thanks for thoughts, comments, and alternate ideas :-)

toolie

Reply to
dave
Loading thread data ...

Ohms per foot:

14 .00297 16 .00473 18 .00751 20 .0119 22 .0190 24 .0302 26 .0480 28 .0764

So... (4) #24 conductors is almost exactly equal to (1) #18 conductor.

The lamps only draw 2 Amps or less, so this should work fine.

Speedy Jim

formatting link

Reply to
Speedy Jim

If I were trying this, I'd use a separate chunk of cat5 with all of the conductors bonded together for each function. That SHOULD be enough to keep things from metling down/burning up. The 14ga. romex will likely be too stiff to work with conveniently, but should do the job fine electrically. 12ga. romex would be even stiffer, but would definitely do the job for pretty much anything short of trying to feed the starter.

Reply to
Don Bruder

How about buying an "outdoor" extension cord, then running a single conductor zip tied to it for ground?

nate

dave wrote:

Reply to
N8N

On a run of 15-20 foot cat 5, you'll probably need to double it up to run the bulbs. If you double up each function, you may have to potentially (double x numberOfFunction) your common ground. It just seems like a lot of wire and trouble because you'll have a wiring tree running to the car behind you the size of your thumb.

It probably isn't super critical, but if I had a choice, I'd use the 14 gauge Romex. It is solid wire so will break if flexed a lot, but it only has to live for a couple of hours, right?

Remco

Reply to
Remco

If it was only one use, then I think the 14 ga would be the way I would go. If I figured on having a set of tow lights kicking around for another day, I would go with the multi wire 24 ga. It isn't that much more work to use multiple lines per load. Stock for most vehicle taillights (1157 bulb) is 18 ga.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

From an electrical engineers prospective. I just look it up in my handy electrical code book.

24 guage has a max. current listing of 3.5 amps. Engineers like a safety rule of 3x so I'd follow the previous advice of and triple up my cat5 conductors which gives me plenty of margin for current spikes and I get 2 wires of 3 conductors each.

My 2cents. Derek Palmer

67 Bug 67 Austin Healey MkIII
Reply to
Derek Palmer

I don't have the handbook -- at what length is that current max listed? One foot?

I've never heard that rule specifically, but I made up one that is basically identical. 3*x (where x is the most, longest time, largest, strongest, etc. humanly possible). I usually use this rule to estimate how long something will take that I've never done before, and it's quite accurate!

Toyota MDT in MO

Reply to
Comboverfish

It's called the "safety factor". Basically, if you design something that will encounter, say, 500 lbs of a particular force in at maximum expected loading, you test and design to sure that item will fail (break) at no less than 1,500 lbs.

Depending on the nature of the structure, safety factors may go as high as 20x.

My wife does this for me! If I say something will take one hour, she allows for three. She calls it "man time" (one hour man time is three regular time).

Reply to
Hugo Schmeisser

She's really on the ball!

Toyota MDT in MO

Reply to
Comboverfish

That certainly explains why my wife's always late... :)

Reply to
Remco

The handbook ratings are for thermal issues and length doesn't matter. At over 3.5 amps the wires getting hot and the insulation starts to breakdown and things short circuit or the wire melts.

The issue with lengths has to do with Voltage drop. The longer or smaller the wire the more voltage you lose at the other end. You might also interpret this as you need a higher voltage to maintain 3.5 amps of current the longer and small the wire is.

This holds true for DC voltages. At higher frequencies (AC) it gets a lot more interesting. Resistance is not constant at higher frequencies. You can look of "The skin effect" on nerd engineering sites.

The comments on safety factors are very true. They vary relative to the risk of injury and cost of the product. I design integrated circuits and there's not much chance I'm going to electrocute someone so we have a 3x factor. Some of my circuits that went to Mars have a much higher safety factor.

Hope that clarifies things.

Derek

Reply to
Derek Palmer

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.