Cable thickness

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Gizz
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Joined: Wed Nov 03, 2010 8:53 pm
Location: Malmo, Sweden

Cable thickness

Post by Gizz »

Hi!

I'm waiting the arrival of the 50:1 High power motors from Robotbits and I was wondering how thick the cable should be that im soldering to the motor?

I'm also wondering if u ever have to change the wires on for example a Lipo pack depending on the amount of motors and stuff connected or are they definately gonna work with anything possible of stuffing into an ant?

Has anyone had any wires burning up in their ant during a battle at all?
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BeligerAnt
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Post by BeligerAnt »

Given the (short) lengths of cables involved and the low currents involved, wire thickness isn't usually a problem in ants.
When you get the motors you will find that you can't realistically solder anything much larger than 7/0.2mm (16/0.2mm at a push) onto the motors.
I have never heard of the wires on a battery pack or servo overheating in normal operation. It may be possible if you shorted the ends of the battery leads together (don't do this!), but then the wires would be the least of the problem!

Calculating required wire gauge is a little complicated for small things like ants. All of the standards are concerned with preventing fire, so calculate the current-carrying capacity for a given temperature rise in the cable (usually 10C).

Of more interest in ants is the avoidance of voltage drop down the cable.
7/0.2mm wire is about 0.5 ohms per metre, so a 50mm length will only be 0.025 ohms. If you use a speed controller with screw terminals, the contact resistance between the terminal and the wire is likely to be of the same order.
So in practice the wire resistance is not a problem and self-heating is likely to be minimal.

Unless of course you're planning something really outlandish... :wink:
Gary, Team BeligerAnt
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philippos
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Post by philippos »

i use 0.75 mm in iAnt and works fine! you can pick it up on kjell and company in sweden :wink:
Philip Johansson ,16

one of the guys from Sweden. :)

Robots: Breeze (Aw, not done yet :P )
Gizz
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Joined: Wed Nov 03, 2010 8:53 pm
Location: Malmo, Sweden

Post by Gizz »

Thank you Gary for the very informative answer, It was even more than I could ask for.


Thank Philip, I got some very thin wires laying around so I have to measure them as the might be perfect actually :)
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peterwaller
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Post by peterwaller »

The one thing you want to avoid is single strand wire.
Copper work hardens which means every time it is bent it get stiffer and slightly more brittle.
If you look at the very flexible wire it has lots of very fine strands but single strand wire in a robot where it can be stressed a lot will soon break.
Gizz
Posts: 64
Joined: Wed Nov 03, 2010 8:53 pm
Location: Malmo, Sweden

Post by Gizz »

Yeah I've come across that quite much at work, hate using single wired cables. The ones laying around is flexible so I'll give them a go :)
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