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deadtetra
11-13-2012, 01:51 PM
Hello, I am a student building a robot for a project and I am having difficulty finding a continuous rotation servo.

I estimate that I need (2) 10 kg./cm. servos for the drive system (we are going to control steering via drive servo, i.e left servo operates clockwise while right servo operates counter clockwise to turn left (or right depending on orientation)).

We ordered (2) 1501MG servos from Polulu.com, and attempted to modify them for continuous rotation (we did this because we were on a budget). But apparently these servos did not like the modifications much because one burned out. We ordered another of these servos and attempted the same modification to the new one and it burned out as well.

Due to lack of time remaining for our project, rather then trying to figure out where we went wrong with our mods, I have decided to simply order continuous rotation servos online, but I cannot seem to find any 10 kg./cm. servos for the price range I'm restricted by (which is <=$20.00 ea.).

Can anyone point me in the right direction? And is there a reason why continuous rotation servos seem to be so difficult to find? Or am I just looking in the wrong places?

Any help is greatly appreciated!

-jay

CasperH
01-07-2013, 10:04 AM
Hi,

For my quadropod robot I have 4 of these at the end of each leg:

http://www.parallax.com/tabid/768/productid/102/default.aspx

Note that they are actually from Futuba, I connected the boebot wheels to them. They have a screw that you can use to "tune" them for their 0 turning velocity at 1500 msec. With the boebot wheels (~3 inch) you can reach a max velocity of ~0.17 m/s.

http://www.parallax.com/tabid/768/ProductID/412/Default.aspx

Another option would be to have a look at servocity.com and add the continuous rotation option (click next to "rotation") but this can get costly (+20 dollar per servo).

http://www.servocity.com/html/hs-422_super_sport_.html

jwatte
01-07-2013, 11:15 AM
I cannot seem to find any 10 kg./cm. servos for the price range I'm restricted by (which is <=$20.00 ea.).

My suggestion is to raise the budget. You already spent more than that on failed servos.
A Dynamixel AX-12 in rotation mode might work, although it (like most hobby servos) will have a "dead zone" where it can't see the wiper from the feedback.
A Herculex DRS-0101 might be another option.
The AX-12 is $45. The Herculex is $36. Compared to the $20 hobby servos, they probably won't burn out, though :-)