Jerky Motors

Today I built a 4wd robot that was basically the tumbler.When i started driving it i noticed that when i tried to turn right the robot would turn right for a second then it would jerk left and start turning that way, Sometimes it would jerk back right or it would continue turning left. It never did this when i was trying to turn left though. Ive never had a robot do this before so i was wondering what you guys think the issue is.

I’m going to guess programming. Our bot had that problem when we were trying some new driving concepts. Make sure you don’t have typos in your code e.g. motor 3 instead of 4 or using the same motor more than once.

I believe there is a problem with the settings in my transmitter because i tried hooking a motor up to the micro controller with the default code and it randomly reversed directions to.

EDIT: I reset the settings in the transmitter and the problem still exists but ive noticed that it only switches directions when i am almost at full turning speed. Also the problem is ONLY on channel 1.

Is the antenna on your transmitter fully extended? How is the antenna mounted on your robot? I’ve seen antenna problems cause random control problems. Good luck.

I lost my antenna tube :mad: so i just have a plastic tie going around the holes of the receiver and holding down the antenna.

I really hope my transmitter isn’t fried!

Ive narrowed the problem down to the transmitter because ive tried it on different motor ports and i also tried it on tether and it did the same thing.My transmitter wasn’t doing this originally so i don’t know what happened. I haven’t dropped it or any thing.

When i built my tumbler, i folded the antenna across the chassis, instead of using a tube/stand set-up, because i wanted nothing to prevent movement while being flipped upside-down.

After experimenting with this antenna set up, i noticed that as soon as i got any type of interference, physical or not, it tended to carry out the current command I gave it on the controller longer than i was pushing the joystick (longer than i wanted it to)

What i think i learned from these experiments is that any type of interference between the transmitter (controller) and antenna greatly affects the performance of the robot.

The best set up I found for mounting the antenna is using the tube/stand set-up on a section of the robot that was not surrounded or touching metal at any point, was more than an inch from any wiring, and was sticking straight up. (I concluded straight up because when i tilted my robot, or flipped it, the connection suffered still)

My conclusions aren’t exactly scientificly accurate, but these things did happen to me.
I hope my conclusions help.

I don’t have a picture handy, but – like a lot of teams – we have more receivers than hollow tubes to hold up the antennas. We use the long Vex wire ties sticking straight up in the air with the antennas attached with small wire ties. Try it – it works amazingly well.

ill try those techniques but i know the problem isn’t in the wireless connection because ive tried it on tether and it did the same thing.

EDIT: today i opened up my transmitter and tested the pot im having trouble with. its basically jumping to 1k whenever the pot reaches 4k

Odd. I’ve actually woven the entire length of my antenna through the holes of a beam on several of my robots, and have experienced no problems whatsoever, except when I failed to secure it and it got caught in my gearbox (oops.) I just figured the frame of the robot would effectively act as an antenna extension if it did anything. never used the sleeve more than once or twice.

so any ideas on how to fix my transmitter because i dont want to spend a 100 dollars for a new transmitter when i could geta new pot for a few bucks

I hate to take a sale away from IFI, but if money is a problem (when isn’t it) I would suggest looking on ebay or I believe I have seen brand new Transmitter Kits for sale on the internet for really cheap prices - around $29 I think. These were the Transmitter Kits sold at RadioShack so that you could have 2 Transmitters to control your robot with.

Anyway, try looking on the internet and see what you can find.