Maaaan...RC s*cks. No stability at all.

[rabi_tagore]

Honestly....I am very upset with the way my RC robot behaves. I have been building my robot for over two months now, and when I plug in individual servos(standard servos that were modified for 360 rotation....they were modified the way this website told me to) into the receiver, the servo works properly(i.e., after carefully messing around with the pot to bring the servo to equilibrium). So after messing around with the pot for I while, I find the eq. position and I place the servos in their respective positions on the robot. And guess what my first test brings out...a jerk, another jerk, automatic movement of one wheel, misplacement of the center of mass, and a crash into the ground.

eq. = equilibrium position, i.e. the servo does not move when I do not press anything on my remote control.
Yes, I am upset after trying to bring the servos into eq. position, and since I glued the pots, it is even tougher for me to bring the servos back to eq. And I desperately want an alternative solution. Please guys, give me some solution to the "jerking" problem. And quickly pleeeaasseeeee, 'cause the contest is on this Saturday itself(Regional Science Olympiad)!!!

And by the way...I am using 6 channels, and 8 servos(2 Y-harness's), which makes my job even more frustrating.

Thanks a lot...to everyone who replies to this message.
________
Tagore.

[ed1380]

if you're really desperate for time then maybe new servos's.

[rabi_tagore]

ohh...new servos? how will that help? They all behave the same...don't they. And I suppose HS-311 is pretty good

[Admin]

Hmmmm so jerking isnt a problem from being off equilibrium, its from interference.

If its off equilibrium, it will move consistantly in one direction.

Interference can be caused by rogue signals, or from inter-servo interference.

Ideas to fix the problem:
dont turn on your robot until your remote is turned on first (when remote is on, reciever ignores more noise)
extend the remote antenna fully (to boost the signal)
twist the servo wires together (i hear this works, although it hasnt for me)
wrap tin foil around your servo wires (insulates against interference)
buy a servo booster http://www.servocity.com/html/boosted_servo_extensions.html

I had a similar experience as you for a competition I entered. The day before the competition, we tested our robot on the testing area. Strangely, we got tons of unexplained jitters in our servos, undoubtably caused by interference. All our competitors complained of the same problem (we were all in a big hotel). Luckily, the noise stopped the next day . . .

from my servo page:
"Noise is often a major source of servo inefficiency and therefore should be avoided. Ever notice your servo jitter or vibrate? This is because your servo is rapidly jumping between two different angles due to interference. What causes this interference? Well the signal wire is no different than a long antennae, capable of accepting unwanted foreign signals and sending them straight to your servo as a command. A common interference source is usually from other nearby servos and/or servo wiring. How to prevent this problem? Keep your signal wire short, meaning do not add say 3+ feet of extension cables to your servo. If you have many servo wires going through one area, and it isnt feasible to keep them apart, then twist them together. Supposedly this reduces cross interference and I've heard it works, although I cannot really tell for sure myself. You can also buy something called a servo booster extension which buffers and amplifies the signal."

[rabi_tagore]

hey...sorry admin. I think u misunderstood my question. The problem for me wasn't "jerking" in the sense that it stays at one place and "jerks." I was talking about something different, 'cause I would not have been frustrated about something as minor as that...lol. U know when u modify a servo for 360 rotation, the pots have to be zeroed PERFECTLY. Otherwise, the servo rotates by istelf w/o any controlling from the remote controller? This was the "jerking" I was talking about, 'cause whenever I turn my robot and my transmitter on, almost all servos start by themselves, and the ROBOT "jerks" up and down without control. (I guess I shd call it "automatic revolution" or something instead of "jerking") Ofcourse, I can zero the pots, but even the slightest disturbance will get the servos starting by themselves.
So...any advice regarding this issue.

Thanks a LOT for typing that much regarding "jerking." It sure helps because I was having the "jerking" problem too, but neglected it in the face of something even more disastrous...lol.

 Please Reply!!
_____
Tagore

[Admin]

i know what you mean, some servos are just really really sensitive, which is why i recommend the glueing.

hmmm does your remote have trimmers on it (im guessing no)? all good remotes have these dials that you can adjust until your servos stop moving, a really useful function to solve just the problem you are having (i have this problem too).

i own two remotes, one has mechanical trim (which i hate), and the other has a really nice digital trim. any chance you can buy a new remote?

[rabi_tagore]

Well, I have a hitec 6-channel transmitter, which has mechanical dialers(i think mechanical -- basically I have to move them up and down to control the servo auto revolution). Yes, I can still buy a new remote...don't really care abt the money. But, u know what, I think the dialers on my remote might turn out to be pretty useful. I guess if I use them better after carefully zeroing the pots with glue, there will be minimal servo auto revolution.

Well, thanks mate...I will glue 'em up, and if there are easier methods(lol...always looking out for 'easy') do mention them...like digital dialers. Can they be bought seperately and installed on to my hitec transmitter, instead of buying a new remote altogether??

Once again, thanks for letting me know quickly!!

____
Tagore

[Admin]

Can they be bought seperately and installed on to my hitec transmitter, instead of buying a new remote altogether??

nope . . . but if you wanted to overcomplicate things, you could probably hack it to be digital . . .

and for those who dont yet own a remote, get the digital ones! they are worth the extra cost.

[Eco19R]

Depending on the servo you can remove the pot and solder in two resistors.

note - if your using a RC controller all the hobbyclass ones have adjustments on the handels to set center positions.