Servo glitching question?

[BrawnFG]

all my servos are analog and buzz away even if I take off the horns if I let 7 volts hit them. Ok, so the servos are rated at 6v, and I was giving them 7v, but still I wouldn't have thourght that would make them glitch (fry yes, glitch no).

as I said, the UBEC seems to sort it out, I just now have the problem that the three servos together seem to pull too many amps foy the UBEC or battery to cope with (don't know which is the limiter). possible solution could be a better UBEC, or a big b*stard capacitor downstream of the UBEC

 

[Trip]

hhmmm I wish I could help, but electrical is not one of my strengths.. I hope you get it sorted.

Did you ever get the servos wet? I know snow made a few of my old analogs twitch back and forth all the time.

 

[Bigger the Better]

How are you getting 7v to the servos? If you are running a BEC then that will not allow them to get 7v.
Your radio or reciever may also have settings for anolog vs digital servos.
NEVER put 7v to a 6v servo or you run the risk of burning them up. The board or motor will melt down. If you have been runnin them at 7v that may have messed with them?

 

[sperera]

my receiver battery is usually over the 7volt mark, only a 5 cell but when full charger will be over, but all my servo's are digital and ive never had an issue, hope this helps.

 

[Sharkey]

i direct power all my servos as well, they get whatever is in the battery, and fully charged its near 7 volts. many receivers don't have a voltage regulator built in for the servos so even if your not direct powering you can have that high a voltage. i don't hear any stories from people burning up servos from over voltage with a 5 cell pack, and 5 cell packs have been the standard for 15 years so its gotta be alright.

 

[Bigger the Better]

Load voltage will be lower.

 

[Trip]

BTB Brawn has his servos wired direct to the battery. I think he is running a 7.4 lipo.

 

[sperera]

ok that changes everything, coz a 7.4 lipo will charge over 8volts.

top end servo's are designed to work on 2 cells, i would be running analogue servo's off a lipo. not without something to bring down the volts and keep it stable anyway.

 

[pipeous]

what is the ubec. might not be supplying enough amps. I run 10 and 15 amp bec's myself at 6v. a servo can easily pull 1-2 amps of power

 

[Killer RC]

What radio are you using? Is this a new issue or has it happened since you've had the LiPo setup?

I've had issues with these LiPo and BEC setups, which is why we started doing the 6.6v LiFe stuff without regulators.

 

[pipeous]

older ubecs used a slower freq shift that would cause noise in the rx. the castle you just stuff shoe goo in the end where the power wires to battery go and they don't pull off the board plugging and unplugging things causing a short inside. the hercules from western robotics is a proven workhorse in the heli community running all them digital servos and a gyro. I've been using bec's in helis a long time and quite a long time in the 5th scales

 

[BrawnFG]

wow a whole thread dedicated to my off topic post has sprung up whilst I was away!!

to recap.......

I have a 5cell NiMh battery. when charged fully the battery kicks out 7v (according to the telemetry on the Spektrum DX3s radio)

if I wire everything into the battery directly, the servos glitch a little, constantly. This may be OKas it is only a few degrees movement, but I just feel a little uncomfy with twitching servos on a 40mph largescale

if I put a BEC (set at 6v) between the battery and all other radio gear, the glitch disappears. Therefore I run with a BEC (the one I have is from fleabay and calls itself a UBEC, I guess U is for Universal as the chinglish instructions yabbered on about taking upto 3s lipo or any other battery you could think of)

The problem I have is that when I run 2x brake servos and a steering servo off the BEC, I see the voltage on the telemetry dropping to 4.5v even with a fully charged battery.
I have not investigated that far yet, but I was wondering if it is most likely to be the BEC that is under rated or if I am being limited by the battery being NiMh instead of LiPo and therefore unable to supply enough current?

 

[Trip]

I swore you said in another post you had a lipo..

I gotta stop smokin the crack.

 

[BrawnFG]

I swore you said in another post you had a lipo..

I gotta stop smokin the crack.

I probably drooled over a LiPo in some other post... (n.b. I wouldn't recommend it to others, LiPos can pack a punch when the drool hits teh connector)

 

[Killer RC]

Once you start using the servos the voltage should drop a little bit and the chattering should stop. I would run it without the BEC. If you have a kill switch there's nothing to worry about, if the servos do act up.

 

[Bigger the Better]

Spectrum units let full power to the electronics, you should not need to run power direct since it already is. I would not use the UBEC at all.