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Interference Between Battery Power and Throttle Leads?

Old 04-13-2011, 03:22 AM
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bsrchas
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Default Interference Between Battery Power and Throttle Leads?

I posted this question in the beginners forum with no responses. Thought I would ask here.

I'm a newbie converting a TopFlite DC-3 to e power. Have to run the two battery power leads and the throttle control leads in very tight cowl spaces for approx 12 inches. Does the amperage running through the battery power leads to the ESC cause interference with the throttle control leads going to the ESC when run very close together like that??

Do I have to be concerned with separating these leads??
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Old 04-13-2011, 03:35 AM
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Bub Steve
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12" is a LONG way to run ESC power wire's, the leads will be OK as long as you don't wrap um together and do try to space them apart to minimize RF,interference, can you stort'in up those's power lead's as you'll need BIG gauge wire's to pull 12', bubsteve
nice look'in
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Old 04-13-2011, 04:52 AM
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bsrchas
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Motors in the nacelles on each wing with the battery in the nose of the fuselage. ESC's directly behind the motors. Haven't measured exactly yet but might be 18" total from battery case to esc case which includes the pigtails on the battery and the ESC's One battery in nose to feed two motors with a Y harness.

It will be very difficult with the limited amount of space to separate the battery power from the throttle leads. They'll be running side by side essentially touching each other for approximately 12 " from each nacelle to the center of the wing where the receiver is located.

Suggestions I'll try to post a photo tomorrow and show dimensions.
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Old 04-13-2011, 05:22 AM
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standing by, bubsteve
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Old 04-13-2011, 07:11 AM
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What type of radio are you going to use?

If the chosen radio is of the 2.4 Ghz type then I would not think that there would be much "interference". If the radio is high or low band 72 Mhz then you might have a serious problem.

Several solutions come to my mind.

You might want to use TWO receivers - one on each side of the plane for controlling the motors. This would/could solve the problems of the connectors running to a single receiver in the fuse easily. This arrangement is done quite often on larger planes and sailplanes.

Use quality ESC's also as the longer leads for the battery might cause a little bit of a resistance problem cutting the battery's efficiency down considerably to where you calculate 5 or six minutes of flight time only to actually have 4. Whoops!

Everything matching as closely as possible is the key.

BTW the use of two receivers is fairly easy no matter what type radio system you are using.

Hillbille
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Old 04-13-2011, 08:16 AM
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JetPlaneFlyer
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I dont think the type of radio will make any difference to the problem. the issue is induced current in the control wire caused by the magnetic field of the high current bettery power lines.. this has nothing to do with radio frequency or radio interference.

Using two Rx's located in the nacelles would solve the proximity issue of the ESC control wires but then you would have the same problem with the servo wires you had to run back to the fuselage to opperate the rudder and elevator.

Is it not possible to create a second route for the control wires slightly seperated from the battery power cables? This should only be a matter of making a few holes in a few wing ribs.

If all else fails you could wrap the control wire with metal foil to shield it, that should work.

Steve
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Old 04-13-2011, 02:19 PM
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DanWard
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In my line of electronic work I often work with low voltage signal wiring in noisey environments. I find twisting the wires tends to cancel the induced voltage cause by the noise. I beleive it is called common mode noise rejection, is that right?

As I understand it by twisting the wire the polarity of the induced noise is reversed evry 180 deg of the twist so noise induced at one place is cancelled 180 degrees later in the twist. Isn't that how it work? Something like that...I used to know the theory hands down but that was many years ago, now I just know ity works so I always do it.

For example all analog signal wire 4-20mA or 0-5Vdc is always a twisted pair. Cat5, Cat6, modbus, and symilar communications wire is always twisted for noise rejection.

Back in the old days (some 20 years ago) most all my servo wires, etc, used twisted leads.

Might give it a try. NOt sure it has an application in model electronics but I've seen it work hands down no doubt about it in electronics at work.
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Old 04-13-2011, 04:36 PM
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Bub Steve
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Originally Posted by DanWard View Post
In my line of electronic work I often work with low voltage signal wiring in noisey environments. I find twisting the wires tends to cancel the induced voltage cause by the noise. I beleive it is called common mode noise rejection, is that right?

As I understand it by twisting the wire the polarity of the induced noise is reversed evry 180 deg of the twist so noise induced at one place is cancelled 180 degrees later in the twist. Isn't that how it work? Something like that...I used to know the theory hands down but that was many years ago, now I just know ity works so I always do it.

For example all analog signal wire 4-20mA or 0-5Vdc is always a twisted pair. Cat5, Cat6, modbus, and symilar communications wire is always twisted for noise rejection.

Back in the old days (some 20 years ago) most all my servo wires, etc, used twisted leads.

Might give it a try. NOt sure it has an application in model electronics but I've seen it work hands down no doubt about it in electronics at work.
Great post here,I still use some of my old twisted lead's, I wonder if ferrite rings would help??
what do you think?,,,the long power leads worry me more that the RF jumble, but with big sil, wire it may carry it,bsrchas has a cool plane ,I can't wait to see this puppy fly bubsteve
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Old 04-13-2011, 06:16 PM
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Originally Posted by bsrchas View Post
Motors in the nacelles on each wing with the battery in the nose of the fuselage. ESC's directly behind the motors. ...but might be 18" total from battery case to esc case which includes the pigtails on the battery and the ESC's One battery in nose to feed two motors with a Y harness....
You might want to reconsider this arrangement.
Recommend keeping the ESC-Battery leads as short as possible; 12 inches or less to avoid overwhelming the filter capacitors and blowing the power FETs in the ESCs. Long leads to the motors are the preferred arrangement; use thicker gauge wire to reduce resistance losses.
Detailed discussion in following thread.
http://www.rcgroups.com/forums/showthread.php?t=952523

Last edited by gyrocptr; 04-13-2011 at 06:31 PM.
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Old 04-13-2011, 08:30 PM
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Bub Steve
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good post, here's a Jumble of wire'in on my foam glider twin's,,bubsteve
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Old 04-14-2011, 03:12 AM
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bsrchas
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Just had a chance to take some photos of my situation. The photo below shows the dimensions for the routing of the wires. The only wiring access is through the tops of the nacelles because the retract system takes up all the space underneath. There is only a small space inside the nacelle and above the wing sheeting to avoid cutting a hole in the main wing spar. I had planned to put the ESC just behind the motor in a plywood spacer I made (not shown) to position the motor forward enough for the right propeller position. [media]http://img691.imageshack.us/img691/3527/c47wing.jpg[/media]This photo shows the distance needed to get the power leads from the battery to the access space in the middle of the wing.
[media]http://img703.imageshack.us/img703/6866/c47fuselage.jpg[/media]I just read the post about placing the ESC's closer to the battery, perhaps in the center space between the wings, and just extending the three motor leads from the ESC. That might work by reducing the interference potential and decreasing the extensions for the battery power but now I have to get cooling air into and out of that space. That's doable. It appears that I will still have to extend the power leads from the battery to the ESC's a little but much less than if the ESC's were in the front of the nacelles.

This is a great forum. Thanks all for your help.
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Old 04-19-2011, 03:55 AM
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OK. I followed the advice from an earlier post to not length the leads from the battery to the ESC's but instead move the ESC's closer to the battery and extend the 3 leads from the ESC's to the motor.

I've done that and now placed the two ESC's in the center section of the wing (see photo in previous post in this thread). Now I'll extend the 3 power leads from the center section to the two motors on each wing.

Now for another possible interference question. Those 3 leads from the ESC's to the motors will be running tight alongside the aileron servo leads for approx. 5 inches. Any concerns over interference there???

First electric conversion for me. Am I worrying too much about this??
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Old 04-19-2011, 05:06 AM
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kyleservicetech
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Originally Posted by bsrchas View Post
OK. I followed the advice from an earlier post to not length the leads from the battery to the ESC's but instead move the ESC's closer to the battery and extend the 3 leads from the ESC's to the motor.

I've done that and now placed the two ESC's in the center section of the wing (see photo in previous post in this thread). Now I'll extend the 3 power leads from the center section to the two motors on each wing.

Now for another possible interference question. Those 3 leads from the ESC's to the motors will be running tight alongside the aileron servo leads for approx. 5 inches. Any concerns over interference there???

First electric conversion for me. Am I worrying too much about this??
Are you running 2.4 Ghz, or 72 Mhz? It's pretty hard to get interference problems with 2.4 Ghz. And the signal levels that lead from the receiver to the servos are several volts in magnitude, so it would be difficult to cause problems with the servos them selves.

But the receiver is another matter. These brushless motors and their brushless ESC's are a lot quieter than the old brush type motors. I had a LOT of problems with those brush type motors and 72 Mhz receivers some 10-20 years ago. Something I ran into with 72 Mhz is the high current noise on the motor power leads got into the servo leads, and back tracked into the 72 Mhz receiver, causing reduction in range. One of my 1200 watt brush type motors running on 38 Nicad cells had a range of about 20 feet with the 72 Mhz transmitter fully extended. Took a lot of work with big ferrite chokes to get rid of that. I'd found that brush type motors running over about 15 Volts DC or so were the ones that really caused problems.

The worst of it was, for some reason the range check would be perhaps 80% of normal with the motor running, but the full range with the 72 Mhz antenna fully extended was only about 500 feet or so. Never did understand that.

But again with 2.4 Ghz, those problems pretty much go away. But 2.4 Ghz does have other issues, namely the receiver voltage and how good your receiver DC supply is. People have tried to use "AA" sized nih batteries in giant scale models to run those servos. The resulting voltage sag on the nih batteries can lead to very serious problems.

Best to use one of those Castle Creations 10 Amp BEC's for receiver power. And, these BEC's weigh less than a good receiver battery.
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Old 04-19-2011, 05:46 AM
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Originally Posted by kyleservicetech View Post
Are you running 2.4 Ghz, or 72 Mhz? It's pretty hard to get interference problems with 2.4 Ghz. And the signal levels that lead from the receiver to the servos are several volts in magnitude, so it would be difficult to cause problems with the servos them selves.

But the receiver is another matter. These brushless motors and their brushless ESC's are a lot quieter than the old brush type motors. I had a LOT of problems with those brush type motors and 72 Mhz receivers some 10-20 years ago. Something I ran into with 72 Mhz is the high current noise on the motor power leads got into the servo leads, and back tracked into the 72 Mhz receiver, causing reduction in range. One of my 1200 watt brush type motors running on 38 Nicad cells had a range of about 20 feet with the 72 Mhz transmitter fully extended. Took a lot of work with big ferrite chokes to get rid of that. I'd found that brush type motors running over about 15 Volts DC or so were the ones that really caused problems.

The worst of it was, for some reason the range check would be perhaps 80% of normal with the motor running, but the full range with the 72 Mhz antenna fully extended was only about 500 feet or so. Never did understand that.

But again with 2.4 Ghz, those problems pretty much go away. But 2.4 Ghz does have other issues, namely the receiver voltage and how good your receiver DC supply is. People have tried to use "AA" sized nih batteries in giant scale models to run those servos. The resulting voltage sag on the nih batteries can lead to very serious problems.

Best to use one of those Castle Creations 10 Amp BEC's for receiver power. And, these BEC's weigh less than a good receiver battery.
I'm using a 2.4 system but what I'm concerned about is the lead from the rcvr. to the aileron servo. Would the 3 power leads to the engine running alongside the aileron servo leads for 4 - 5 inches in each wing mess up the aileron signal?? I was thinking that the signal going through the servo leads would be the same for 2.4Ghz vs. 72Mhz systems.
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Old 04-19-2011, 05:56 PM
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Originally Posted by bsrchas View Post
I'm using a 2.4 system but what I'm concerned about is the lead from the rcvr. to the aileron servo. Would the 3 power leads to the engine running alongside the aileron servo leads for 4 - 5 inches in each wing mess up the aileron signal?? I was thinking that the signal going through the servo leads would be the same for 2.4Ghz vs. 72Mhz systems.
You are correct, the signal going through the servo leads is identical for both 2.4 Ghz, and 72 Mhz. This signal is a voltage pulse of three or four volts (depending on brand of receiver) in magnitude, and from one to two milliseconds wide, depending on the position of the related transmitter stick. It repeats about every 25 milliseconds or so.

Cross coupling between wires can be an issue IF one of the wires is carrying very low voltage signals, such as audio from a microphone or something similar. With this type of stuff, a millivolt of electrical noise can be a real problem. That's one reason the various audio cables between your stereo, CD players, VCRs, and Television use much higher audio voltages on the order of several volts. Really gets rid of hum problems and so on.

But with the several volts involved with servo signals, a millivolt or three of noise from your power cables will not even show up.

FYI, those guys who fly high powered electric sailplanes with their very narrow fuselages probably have their wires crammed in a lot more than you do . And some of them are really running a LOT of power.

Hope this helps.
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