Servo jitter
 

ok, my servo sometimes jitter when the transmitter is off and receiver is on, if both the transmitter and receiver are on, the jitter stops. Is that normal?

RE: Servo jitter
 

This is normal. HOWEVER you are not supposed to have the RX on and The TX off you could damage the gear trains on the servos.

The correct Sequence for Turning on is Check the Freq Board Get reserve the Freq Turn on TX and Then RX
To turn off its RX first then the TX then reqlinsh the Freq (PIN)

One of the first lessons my Instructor taugt me;):D:D

RE: Servo jitter
 

It is normal, but as Crashem said you shouldn't let it happen. What is happening is that your receiver is picking up stray radio signals and translating them to movement, hence the jitters. When you turn you transmitter on the receiver locks on that signal and the jitters stop. The reason you want to turn on the tx first is because the rx can pick up a stray signal and command the servos to move to the point that it can damage the servo.

Hope this helps.

RE: Servo jitter
 

That's what I thought, I had forgotten about the order!! Thanks!

Now heres another weird event that happened yesterday night. I installed a aileron servo on the wing of my Spad Debut and when I started testing the aileron movement my servo would move, not jitter but really move fast from one side to the other by itself... and then center itself and stop after 1-2 seconds. Of course, I freaked out and was almost sure my servo had damage done to it or something... and I didn't want to go out and buy another radio or wait a couple of weeks for a servo from JR to by shipped to me or something.

So I took the servo out and placed another one and it worked fine, so I know that the problem is the servo and not the transmitter or receiver.

Before going to bed I decided to take another look at the servo, this is what I did to it. I took a hammer and smashed it... ;) ok I'm just kidding of course.. While the tx and rx were off, I moved the servo motor by hand all the way clockwise. Turn everything on, could not move anything, looked like the servo was now really broken. Being the type of person who doesn't give up easily, I turned the rx and tx off and move counterclockwise... Turn everything on and now I could move and the servo is working perfectly fine (No turning around a few times and centering itself)

Now, can someone explain to me what happened? :)

RE: Servo jitter
 

Sound like you moved the servos pot (I believe thats the correct term) On my Airtronics servos if you remove the gears and turn the top of the spindle you can get them to only work in one direction or reduce the overal movement travel. Its been many years since I purposely messed with a servo so I could be mistaken.

RE: Servo jitter
 

It's called a "feedback potentiometer". It tells the amplifier the position of the output shaft(electrically). The amplifier then determines what command to give the motor to get to the desired position. Sometimes they(the pots) get dirty or worn and this may cause jitters as the servo "hunts" for the proper position to obtain a "null" condition.

RE: Servo jitter
 

Are your receiver batteries fully charged? I've has jitter servos before when the battery vltage is low. Try charging them up completely and you may find the problem goes away.

RE: Servo jitter
 

I have a question, If there was a radio on 95.1 or whatever megahurts(SP), Would the radio station signals interfere? I have always wondered this.

RE: Servo jitter
 

Newb,
Not in the US. The FCC manages frequencys and the radio station won't interfere with your radio. The most likely culprit for interference for us would probably be from pagers.

RE: Servo jitter
 

Hamm radio is suspicious. I think especially here in Alabama. FCC does not look to hard in houses in Alabama, USA. I know Hamm has FCC regs too, but I know several at a club have crashed in unison and there is a tower; near to the field; next to a trailer that worries everyone. I have lost one that was PCM...hovering...failsafe no good for that one. Intresting...sad....impressive death.
Oddly enough trains too. At least where I am and my frequency....whatever... I hear it coming and land. A signal will precede it that will throw my PCM's into failsafe. Give me a real workout with the FMs. Took me a few times to figure that out.
Place where I fly by myself mostly. 100 yards from a track on the backside. Could be the harmonics of the trains main or wheel motors, transmission signal, its a mystery that I can nip in the bud...land and wait.
I have had one servo do the extension thing too, flying...then loop, loop, loop..then level, no stick input. Never saw a problem in that new Futaba servo for the elevator. Never would do it on the table. I changed frequncies over that before I figured out the problem. My first plane. Be thankful it did it on the ground. I still fly that first trainer plane with Hitec 635's.

RE: Servo jitter
 

Trains send out radio signals that turn on the crossing guards. This might be a source of your interferrence?

RE: Servo jitter
 

Trains also send out (un-intensionally) a broad spectum of RF interference caused by their metal-on-metal vibrations. Those heavy wheels pounding the tracks produce some pretty good RF.

RE: Servo jitter
 

I think I would have to take that servo apart (with a screwdriver!) and have a good look at the gears. It's possible one or more is stripped.

Andy

RE: Servo jitter
 

Found a interesting article for people who are interested! Theres a couple of paragraph on how servo works.

http://www.hvwtech.com/appnotes/servos_allabout.asp

RE: Servo jitter
 

The AMA did A check on pagers and cell phones and found no problems at all. I think if you go to there site you can look up the results.

RE: Servo jitter
 

To clarify some things....pagers ARE liscensed to operate in the 72 MHz frequency band. Our R/C channels are spaced between the commercial-band channels that are used by pagers, fleet operators, radio-controlled cranes, highway patrol, emergency vehicles, and so on. We've had several pagers over the years that have caused some R/C channels to be unusable.

As far as cel phones are concerned, or other types of radio ransmitters, while their actual channels won't get R/C models, if the transmitter is close and powerful, then harmonics can get into our stuff. Some high-frequency signals can even get in to other parts of a transmitter or receiver and disrupt them.

TV channel 4 is just below the 72 MHz band. If you have a TV channel 4 transmitter near, then it can affect a lot of the 72 MHz band.

One problem with all this is that R/C use is secondary to any other use. If there are frequency problelms, the R/C'er can't complain. Just go somewhere else or use a different channel that's cleaner.

Bill Baxter, Manager
Hobby Services/Futaba Service
3002 N. Apollo Dr. Ste. 1
Champaign, IL 61822
USA
Service Phone: 217 398-0007
Email: hobbyservices (at) hobbico.com