Continuous Rotation Servo

[Cutch]

I have just modified a Tower Pro MG945 servo for continuous rotation. Removed the gearing stop and pulled the pot out of the geartrain so that it can't feedback.
I found that the pot adjustment to get it to stop when the stick is in neutral, is very touchy. I get it set, run the servo in both directions just fine, but it sits jumping in one direction or other. If I flick the stick a couple times, the servo stops jumping for a few seconds and slowly starts to move. Is this a Tx/Rx problem? Does anyone know a fix? The only way I can guarantee that it stays stopped is to cut the power from the receiver. (Skysport 4 Tx/Rx) Thanks.

[Rottenbelly]

I had the same problem when I did one and I was using futaba radio. I ended up ordering a nice hitec from servo city. They have it as a option on some servos and a few for that actual application.

[lsone]

Here you go guys. We use this in the crawler world for a tough, no drift(what you are fighting currently) operation of a winch servo. The member is great, I run his no drift controller along with many other guys. This is the only way to link to him.

http://www.crawlcanada.com/forum/showthread.php?t=9072&highlight=winch+controller

[properchopper]

Glad you brought this up. I'm experiencing the same problem using various [ EXI & Turnigy] digital coreless servos only with my Futaba 3 PM radio; twitching on-center. I read about some of these servos not being compatible with Fut systems in the description section of some Hobby King servos. I'm hoping to find a solution !

[Cutch]

Thanks for the help Rottenbelly. What Hitech did you get?

[Cutch]

Thanks for the help Izone. This guy has a lot of neat stuff.

[Cutch]

Does anyone know of a switch that could run on a spare output to cut power to a servo when not in use?

[CornelP]

When you modify a servo for continuous rotation, there are a couple of things you should do to avoid what you are experiencing. Easiest solution is to remove the pot completely and replace it with a couple of fixed resistors, but these have to be very good quality... I got about 5-10 of them and measured a pair to very close values.
The original pots are quite low quality, the carbon layer is very narrow, hence very sensitive. So another solution is to change it with a larger one or, as I did on a scale boat, replace with two good quality trimmers.

[Rottenbelly]

Thanks for the help Rottenbelly. What Hitech did you get?

I ended up getting a 645 in continuous rotation. It was 20 more bucks but was worth it. I used it as a winch on a crawler i had. was nice and strong.

[Rottenbelly]

Does anyone know of a switch that could run on a spare output to cut power to a servo when not in use?

I am not sure how it would work with cutting off a servo, but i use these to turn my lights on and off with a spare channel.

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=8833

[Cutch]

Thanks ComeIP
I didn't know if you could get resistors identical enough. Do you connect both to where the centre of the pot used to be? Saw one guy using 2.4k. Sound right?

[CornelP]

Correct, you are just cheating the electronics, simulating 50% travel. The 2.4 is what most people recommend. I used different values because I had them on stock :p
See this article:

http://www.acroname.com/robotics/info/ideas/continuous/continuous.html

[Cutch]

Sure looks like it would work. Using a continuous rotation servo to run a fishing reel. I'd like to shut it off to guarantee that I don't accidentally run it when I'm doing other things.
Thanks

[Cutch]

Has anyone used the Turnigy switch to control the power lead on a servo?

[Cutch]

FYI guys. I got a Turnigy switch, hooked it in the power (red) to the servo and it works great.
Thanks Rottenbelly