servo jitters at very slow speed

[motoj550]

i have a spektrum S6100 high voltage servo that jitters at very slow speed on steep inclines, but as soon as i give just a little throttle it quits, other than that everything works fine. i just wired this servo direct to 2S lipo. before i had it wired with a bec direct to the servo and had no issues at all, this jittering started as soon as i wired direct to battery. just a thought though i also moved the sr200 receiver taped to the top of my cc micro sidewinder and i've seen a lot of guys mount receiver on esc with no problems but could this also cause whats going on, any help please, got a comp in 1 1/2 weeks.

[ik632]

I have a few Hitec that do that as well. Mine are searching for center (or position) and jitter. When you hit the throttle and go faster, there's not as much load on the servo because the wheels are rolling faster so you don't hear it struggling.

It's pretty common for digital servos to do that. I was thrown because I always had analog servos until recently.

[motoj550]

let me explain my version of a jitter, my tires move back and forth maybe an 1/4", it never did it with the bec, now that it's wired straight to the battery it started doing this. i've been running digital servos for a while now in most of my crawlers, digitals make a little buzzing noise and kind of vibrate a little, this is different.

[motoj550]

OK i wired in a ground wire from servo to receiver and that didn't do anything. Soooo i put the bec back in wired to the servo and now everything works fine again, whats up with wiring it straight to the servo not working?

[monkeymagic9]

Originally Posted by motoj550

OK i wired in a ground wire from servo to receiver and that didn't do anything. Soooo i put the bec back in wired to the servo and now everything works fine again, whats up with wiring it straight to the servo not working?

it's friday so i'm having trouble thinking while drinking but are you asking why you can't wire the servo straight to the +/- outputs of the bec? like with the servo +/- wires going to the bec and just the yellow wire going to the rx?

if yes, then in short it's because you end up with all sorts of floating ground glitches as power finds it's way down paths it's not intended to go. not a lot of power, but it's enough to skew a signal to isht.

[spillproof]

I just finally figured this out myself. You have to link all the ground (black) wires. I made a bypass and it was glitchy until i connected the ground lead to all 3 connectors, and the power line between bes and servo.

RX plug (male) - Signal and Ground
BEC plug (female) - Power and Ground.
Servo plug (female)- signal, power, and ground.

The three grounds are all soldered together. It works like a charm.

[Charlie-III]

Originally Posted by spillproof

I just finally figured this out myself. You have to link all the ground (black) wires. I made a bypass and it was glitchy until i connected the ground lead to all 3 connectors, and the power line between bes and servo.

RX plug (male) - Signal and Ground
BEC plug (female) - Power and Ground.
Servo plug (female)- signal, power, and ground.

The three grounds are all soldered together. It works like a charm.

What radio are you running?

motoj550, what radio are you running?

I'm just curious since it's a fairly common issue (with ground loops) on Spektrum radios.

Futaba & GT3B/C's don't seem to have the same issue. I'm not sure why, but ground glitching seems to happen more with some brands than others.

[spillproof]

GT3B, hacked. 3ch rx.

[motoj550]

Originally Posted by Charlie-III

What radio are you running?

motoj550, what radio are you running?

I'm just curious since it's a fairly common issue (with ground loops) on Spektrum radios.

Futaba & GT3B/C's don't seem to have the same issue. I'm not sure why, but ground glitching seems to happen more with some brands than others.

i'm running a DX3r with SR300 receiver

[Charlie-III]

Thanks for the replies.

I'm not surprised on the Spektrum issue, sorta surprised on the GT3B.

Thanks for the info though.

[motoj550]

so running the ground to all soures like the battery, servo, and receiver should fix the problem.

[Charlie-III]

Originally Posted by motoj550

so running the ground to all soures like the battery, servo, and receiver should fix the problem.

It won't hurt. At a minimum, make sure the servo is grounded to the RX.

[spillproof]

I think it is either the BEC, or the BEC in the ESC is causing the isolated ground between the electronics, causing the glitching. I think any RX will behave the same with different grounds between signal and power. Just glad that bridging the RX and BEC grounds fixes it...

[motoj550]

tried running the ground to all sources and still does it, put bec back in straight to the servo and no more problems, guess i'll just run the bec and be done. maybe the spektrum s6100 servo is just power hungry (it is pretty stout at 361 oz and .11 speed) 0n a small Gforce 2s lipo 350mah 20c battery, but with bec in no probs.