Wire Length

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clockit
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Wire Length

Post by clockit » Sat Jan 17, 2015 8:27 pm

I wasn't sure where to put this so I put it here...

I've just started my 1000 x 1000 upgrade for my 2 and I'm curious if those that already done so maintain equal length wires for all of your steppers. When I originally built my 2 in the stock configuration I left all of my leads the same length. The only obstacle was that my right side stepper have a lot of wire left over but was manageable. I just rolled it up and put it behind my electronics enclosure, problem solved.

Now with the upgrade, in order to maintain equal length I'll have a lot of wire on the right side Y to deal with. With that being said, if you did in fact cut your leads to 'as needed' lengths for each stepper, have you ran into any issues with your steppers being sligthly out of sync when cutting? Am I just over thinking this?
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cvoinescu
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Re: Wire Length

Post by cvoinescu » Sat Jan 17, 2015 8:42 pm

They would not be "out of sync", because that would imply that the current takes longer to travel over the longer wire, so that stepper lags behind. While that is indeed the case, I assure you, electricity is hundreds of millions of times faster than would make even a barely noticeable difference.

No, the problem is, if you wire the steppers in parallel to a single driver, the resistance of the wire is a non-negligible fraction of the impedance of the coils, so if the cables aren't roughly equal, one motor will get more current than the other, so they would not develop the same torque. That's just a waste of power, because the axis will be as strong as the weakest motor. The difference isn't substantial, though, so I would not worry too much. (Personally, I don't worry about this at all, because I have two Y drivers, one per motor.) :ugeek:
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WillAdams
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Re: Wire Length

Post by WillAdams » Sat Jan 17, 2015 8:52 pm

l considered that and maybe even posted about it.

Given that GPS is the first engineering project to require both the general and special theory of relativity, it's just not possible.

http://what-if.xkcd.com/67/

The electrical consideration is something else as Catalin noted and is on the wiki: http://www.shapeoko.com/wiki/index.php/ ... ire_Length
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clockit
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Location: California, MO

Re: Wire Length

Post by clockit » Sat Jan 17, 2015 9:46 pm

cvoinescu wrote:No, the problem is, if you wire the steppers in parallel to a single driver, the resistance of the wire is a non-negligible fraction of the impedance of the coils, :ugeek:
not going to lie, while I read that for the first time I was like, "what?", lol, but it sunk in on the second pass. Thx cvoinescu, that makes sense to me know, appreciate the much needed help...

Wil, I read the wiki and it did help, I guess I was trying to understand at what point it really becomes an issue... always appreciate your help
Shapeoko 2, Full Kit #7071, Makita RT0701C Router, 1000 x 1000 upgrade, Acme Z Axis w/Nema 17 Belt Drive

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