Servo's go crazy when prowering up [SOLVED]

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shaun2029
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Servo's go crazy when prowering up [SOLVED]

by shaun2029 » Wed Aug 24, 2011 7:29 pm

Help needed.

My helicopter servos started twitching during flight.
These twitches were occurring at a rate of 1 every 2 minutes.
I am running 35Mhz so I installed a ferrite core.
I then managed to fly for about 4 minutes before my
gyro died (KDS 800), replaced it with an Assan GA250.

Now when I test on a turntable at 25% power all seems good.
When I go to 55% the servos all seem to twitch randomly.
The tail servo as well as the other three servos.
I tried without the gyro connected but it did not help.

Could this be the ESC?

Thank you,
Shaun
Last edited by shaun2029 on Fri Aug 26, 2011 12:53 pm, edited 1 time in total.
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paulsouthport
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by paulsouthport » Wed Aug 24, 2011 7:39 pm

Hi mate

What servos and ESC are you using?
Also, where is your antenna and RX in relation to the other electronics, including motor?

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madski
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by madski » Wed Aug 24, 2011 7:55 pm

Hi

I had a very similar experience with the servos having a mind of their own and found that it was being caused by my lipo charger being on causing interference.
Have a look at the following post http://www.heliguy.com/Forum/crazy-servo-t62347.html the explanation of what was happening is near the bottom, plus there is some very useful advice from others in the post.
Happy hunting

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shaun2029
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by shaun2029 » Wed Aug 24, 2011 8:00 pm

Thanks for the reply.

After the first twitches I moved the antenna further away from the ESC and power cables. I have also moved the ESC from the bottom of the helicopter to the front on the opposite side to where the antenna is mounted.

All this made no difference.
I am using Tower Pro servos for the cyclic and a EMAX ES9258 tail servo.
The ESC is a 40A Tornado.

The issues only start when the power goes from 25% to 55+%.

Thanks again,
Shaun
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shaun2029
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by shaun2029 » Wed Aug 24, 2011 8:19 pm

Thanks for the theory.
My charger happened to be on when I tested.
Turned it off but still same issue.
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paulsouthport
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by paulsouthport » Wed Aug 24, 2011 8:22 pm

It does sound like interference, possibly from the ESC or motor. Another possibility would be a problem with the ESC BEC, but I'd go with interference first.

I don't suppose you have spare ESC, RX and motor you could swap out one by one?

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by benjomeen » Wed Aug 24, 2011 8:22 pm

check crystals aint loose . check ant is not touching any metal . any metal to metal moving connections can cause interferance . servo link arms on nitro engines using metal push rods used to do that . check ur ant is tight in your transmitter . personallly i would take the heli and tx to a model shop and ask for some new crystals and try them before you but tell them you have interferance problems . thay should let you try some crystals if they are canny guys

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shaun2029
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by shaun2029 » Wed Aug 24, 2011 8:49 pm

Thanks for the advice people.

The receiver does not have a crystal. The antenna is not touching any metal.
I have ordered a ESC and will try it and report back.

Shaun
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shaun2029
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by shaun2029 » Fri Aug 26, 2011 12:58 pm

benjomeen you get 10/10.

The antenna was touching metal in the form of a carbon fiber tail-fin. The carbon cut through the antenna insulation.

When vibrating at a high head speed the antenna would short to the tail-fin and cause the symptoms I experienced.

I now know that I committed a rookie mistake when connecting the antenna.

Thank you very much,
Shaun
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benjomeen
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by benjomeen » Fri Aug 26, 2011 2:15 pm

Use a elastic band and make a loop in ant at the end then attach it to the tail fin so its not touching the fin directly . I can do a picture if you don't understand

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shaun2029
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by shaun2029 » Fri Aug 26, 2011 9:04 pm

Thanks, I have attached it using a cable tie but like the elastic band idea. It will allow for easy removal and insulates at the same time. I will use an elastic band tomorrow.

I think i understand how but a picture will be useful.
Thanks for the offer.
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benjomeen
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by benjomeen » Fri Aug 26, 2011 10:02 pm

Image

drawing skills not great but hope this helps

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shaun2029
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by shaun2029 » Sat Aug 27, 2011 5:49 am

Thank you, very helpful.
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