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Old Jan 13, 2013, 12:03 PM
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Where to extend the wires - the final word on where to mount the ESC's?

So what is it guys and gals, should I extend the wires between battery/controller and ESC's or between motors and ESC's?

The Mega Index thread says this with some backup from a Nasa engineer:

Quote:
The ESCs will perform better when cooled by the airflow of the props. Longer motor side lead length does effect the back emf detection of the controller, so the longer the leads, the less accurately and efficiently the motor will be run.
So if you need to lengthen wires in a specific installation, doing it between battery and ESC is the safest approach and in a multicopter application has the additional benefit of offering cooling air from the prop wash.
But I've seen several posts advising the exact opposite, not to mention that most builds seem to have the esc's mounted in the center rather than under the motors.

So what's the deal?
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Old Jan 13, 2013, 12:40 PM
AVR Dude
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Have a look at this thread. It may help.

http://www.rcgroups.com/forums/showt...ghlight=extend
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Old Jan 13, 2013, 12:56 PM
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Originally Posted by Steveis View Post
Have a look at this thread. It may help.

http://www.rcgroups.com/forums/showt...ghlight=extend
Thanks! So basically nobody knows and everyone just does whatever they think is right and it all seems to work just fine.
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Old Jan 13, 2013, 08:36 PM
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My feeling is that we're not talking about large enough distances for it to really make any difference. Sure the theory says it does, or can, but in practice everything seems to run fine.
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Old Jan 13, 2013, 09:04 PM
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Regarding EMF detection, those pulses and EMF return pulses are travelling up and down the motor side leads at around ~85% the speed of light for a single insulated copper wire.

With the EM wave travelling at such high speeds, and the small distances involved in model airframes namely a few centimetres at most, it really wont have any noticeable effect.
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Old Jan 13, 2013, 09:37 PM
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I'd say this guy's been pretty thorough on explaining his point of view regarding this topic.
http://www.rcgroups.com/forums/showthread.php?t=952523

Coming from helis, there's ample evidence of high occurrence of ripple currents that are produced by long battery leads but only in extremely high voltage applications. The flyers that encountered this issue were flying 12s (2 6s in series) and because of the orientation of the batteries, one was really short and one was really long and it was the long one that caused all the ripple currents.

So what that all tells me is...at the voltages we fly - it doesn't matter which side you extend. For other practical purposes, I shorten the battery leads, lengthen the motor wires, and locate the ESCs as close to center as possible. We're talking grams here, but I like to locate that weight as close to the center as possible to reduce the lever effect.
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Old Jan 13, 2013, 09:50 PM
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Well, in theory it's better to put esc near your motors.
Why?
Because in the output of the esc you have a kind of Altern Current and in the imput you have Direct Current.
BUT, the ditances are very short and frequency to low to see any diference.

I prefer put near motor because:

1 - It have more "fresh air"

2 - As I use an external BEC (I take out the BEC of the esc) I have to extend 4 wires = 2 thick wires (+Bat and ground) and 2 thin wires (+5Volt and signal) . I realize that I save some grams than extending 3 thick wires.

3 - It´s more easy to access to you esc.

anyway, I guess that with one or other you will get similar results.

Regards!
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Old Jan 14, 2013, 12:00 AM
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Quote:
Originally Posted by faccan View Post
Well, in theory it's better to put esc near your motors.
Why?
Because in the output of the esc you have a kind of Altern Current and in the imput you have Direct Current.
BUT, the ditances are very short and frequency to low to see any diference.

I prefer put near motor because:

1 - It have more "fresh air"

2 - As I use an external BEC (I take out the BEC of the esc) I have to extend 4 wires = 2 thick wires (+Bat and ground) and 2 thin wires (+5Volt and signal) . I realize that I save some grams than extending 3 thick wires.

3 - It´s more easy to access to you esc.

anyway, I guess that with one or other you will get similar results.

Regards!
Agree with what you say with one further point to consider Magnetometer is significantly affected by the varying static magnetic field created by the wires on the DC input side of the ESC, almost no effect from the motor wires
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Old Jan 14, 2013, 11:43 AM
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Thanks for the info guys, it's clear that not everyone agrees on the issue but I think I'm just going to mount them inboard unless for some reason that turns out to be impractical.

There are some pretty nice builds out there and they can't decide either:

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Old Jan 14, 2013, 04:09 PM
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Originally Posted by jabram View Post
Agree with what you say with one further point to consider Magnetometer is significantly affected by the varying static magnetic field created by the wires on the DC input side of the ESC, almost no effect from the motor wires
Excelent point Jabram.. As I use a kk2.0 (no magnetometer at all) i never have in mind this issue.
But for those that has a Magnetometer a work around would be twist the DC cable to reduce the efects.
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Old Jan 15, 2013, 10:13 AM
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I like this thread, great question and topic OP.

I personally like to run any power, be it surface or air vehicles, as far away from boards and rcvrs as possible. I'm building a FPV platform at the moment and I was wondering about the same question you asked.

So here's my thoughts and please chime in if any of you have suggestions.

I'm going to mount my ESCs out on the DJI arms as close to the motors as possible. The battery for the motors will be out back on the spider frame so I'm also going to mount the PDB in the back half as well. Mount the FCB up front and rcvr and Video Transmitter on the top of the frame....

So I've been researching a lot and I find more and more people talking about twisting the wires. Both for servo wires from ESCs and gimbals. So, my question is; Is it a good idea to twist every type of wire I have running on the quad?

Thanks
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Old Jan 15, 2013, 10:25 AM
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I find this thread interesting, albeit from a different point of view. One of my other “hobbies” is audio equipment, and there is a long standing debate about inter-connect wires and speaker wire. Some swear by twisted and even braided wires for noise rejection, while others maintain it makes no difference. Also keeping the wires away from components & such, so as not to mar the signal.
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Old Jan 16, 2013, 03:44 AM
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I'll definitely braid the wires but I won't go overboard. I've seen some builds with tightly braided wires all the way to the motors, it looks nice but imagine how much extra wire is needed because of the braid. On an octa that would probably be several meters of extra wire.

I reckon a loose braid would mean a minimal amount of extra wire while still minimizing RF noise.
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Old Jan 16, 2013, 10:17 AM
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Oh yeah, that's another good point right there. The extra wire = weight.... Hmmmmm.

So, what about all the servo wires coming from ESCs and gimble servos? Do any of you split them all the way to the source and then braid them?
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