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Author Topic: Motor interference  (Read 2998 times)

rp6705

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Motor interference
« on: April 04, 2007, 01:31:28 pm »

Hi all, fairly new to the forum so please bear with me, i have installed two mfa geared motors in my D.U.K.W and all receiver/servo cables, i have kept the motor cables away from any receiver cables but as  soon as the vehicle gets up to speed the motors tend to stop and start i think through some kind of interference, as anybody got any idea what this could be????
Many thanks

Russ
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DickyD

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Re: Motor interference
« Reply #1 on: April 04, 2007, 03:14:43 pm »

Hi Russ
Are your motors suppressed ?
If not try this site and click on "Articles"

http://homepage.ntlworld.com/fast.electrics/caps.pdf

Richard ;)
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barriew

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Re: Motor interference
« Reply #2 on: April 04, 2007, 05:42:03 pm »

Do you have a separate Rx battery or are you using a BEC ( taking power off the drive battery)?

Barrie
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6705russell

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Re: Motor interference
« Reply #3 on: April 04, 2007, 08:01:06 pm »

Thanks guys, yes i have suppressed the motors and i am taking the power off the drive battery, do i need to go the BEC way?
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dougal99

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Re: Motor interference
« Reply #4 on: April 04, 2007, 08:07:02 pm »

If your RX power is coming from your drive battery you are probably already using a BEC. How is it wired up?

Doug
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6705russell

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Re: Motor interference
« Reply #5 on: April 04, 2007, 08:14:01 pm »

Apologies Doug, i have a 4.8 volt battery pack powering the receiver, one speed controller doing both motors ( drive wheels)  and a seperate speed controller powering the motor/prop.
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dougal99

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Re: Motor interference
« Reply #6 on: April 04, 2007, 08:31:58 pm »

Using a BEC shouldn't make a difference however, you should check that your speed controller is not expecting (ie wired up for) a BEC as using a BEC and a separate battery can cause odd problems. Also if you do go the BEC route only one speed controller needs to be wired in.

If that isn't a problem then you may have an intermittent connection that only breaks when the motors are at speed. This may be caused by the motor mounts moving a little when the speed gets up. Just a thought.

HTH

Doug
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Stavros

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Re: Motor interference
« Reply #7 on: April 04, 2007, 11:24:16 pm »

Just a valid point but are your speed controller man enough for the job it sounds to me that it is them that are breaking down more than motor interferance Stavros
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rp6705

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Re: Motor interference
« Reply #8 on: April 05, 2007, 07:13:02 am »

Thanks for the info Stavros, according to manafacturers the motors only pull just under 1 amp each so i have linked both of them to a viper 15 amp speed controller, do you think this is the problem?
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roycv

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Re: Motor interference
« Reply #9 on: April 05, 2007, 11:14:37 am »

Hi just a thought but you might be having interference from the mechanical part of the drive to the wheels.
Does the DUKW work OK in the water with prop only?  If so this may point to driving the wheels.
If it is in the drive from the motor to the wheels you may be able to get over that with earthing across all mechanical joints with an earth bonded wire.  Don't forget the wheel steering mechanism.
good luck
Roy
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Doc

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Re: Motor interference
« Reply #10 on: April 05, 2007, 12:27:10 pm »

Since you are using a separate battery for the receiver you do not need, and shouldn't be using the ESC's BEC.  UNless you disconnect the power lead in the ESC's cable to the receiver, you will still have the BEC trying to furnish power to the receiver, which is not good.
It appears that you have two choices, remove the separate receiver's battery and use the BEC (only one of them), or, disconnect the BECs and use the receiver battery.  Give one of those a try.  If it works, then which ever you didn't select ought to work too.  Use which ever you prefer.
For some further guessing, since the problem only shows up when trying to run at full power, I'd have to guess that the 'main' (motor) battery is a higher voltage than the receiver's 4.8 volts.  Am I right??
 - 'Doc
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Telstar

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Re: Motor interference
« Reply #11 on: April 05, 2007, 01:54:44 pm »

Hi Russ
Just a silly suggestion. but since the start stop interference is only while traveling on the ground at speed, could there be a loose or bad connection in the battery to motor circuit? (my thinking is maybe jolting is causing the problem).
I would try Roy's suggestion, try it on water, this will at least test that ESC/ motor, and also measure the actual current taken by the motors ( not easy without a rolling road) the current taken by a motor is not always what the maker states, I am lead to believe on land vehicles (buggies) the current varies widely with changes in terrain acceleration etc. much more than in boats (you don't get many hills on lakes).
Recently a fellow modeler had problems blowing fuses on his new twin screw lifeboat, he had got the usual help, using BEC on both ESC's , use BEC on one ESC only ( the correct way I think), using separate Rx battery and no BEC. When we measured the current in his 8A motors we found on full power they peaked just over 12A enough to blow his 12A fuse. Uprating the fuse to 15A then checking the motor temp after a sprint on full power they showed no excessive heat any where.

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