How to modify a servo motor for continuous rotation ( One motor walker robot )

This instructable is part of the one motor walker.
http://www.instructables.com/id/How-to-build-the-one-motor-walker/

There are trillions of tutorial like this, I know :-)

They where taking at school during lunch break with a Sony Mavica camera ( floppy disk )!
5 febuary 2001, 12:18:50

Step 1 How to modify a servo motor for continuous rotation ( One motor walker robot )

The recommended tools for this project:
1 x safety glasses!!
1 x soldering iron
1 x desoldering pump
1 x wire strippers
1 x side cutter
1 x scissors, knife, x-acto, etc

You will need a set of screw driver to remove the four screws on the back of the servo.

Comments

[toywizard]

I have used a wood burner / solder iron and melted these off before.

[Gelfling6]

I've done that too, and would rather stick to the clipper/file method.. You don't have to make a massive deep cut to remove the entire stop from the drive gear, I think the person breaking the gear in this mod, might've been cutting down too deep (below the gear side), or the gear itself was a fairly brittle plastic. A sharp pair of diagonal cutters, just about at the gear side surface, then careful filing (or even sandpaper, though I would wash all grease off the gear afterwards, to remove sand or plastic grit)(then again, you should even after filing to remove the plastic grit that could fall between the gear teeth.) to bring the old stop point level to the side of the gear. (no need to cut it deeper, nothing is going into the recess between the side & the shaft.) Melting, as I'm sure you've seen, leaves a blob on the sides of the place it melted, and unless you carefully remove them (screw driver tip, or clippers (yes, clippers) you run the risk of widening the stop point, instead of removing it. Careful scraping with a hobby knife (X-acto, or even a single-edge razor blade used with care) you could whittle the stop down too.

[a480641]

or one could use a dremel. thats what i did

[toywizard]

I know this is a little off topic but................Besides modifying servos, I have modified antenna rotor motors so I could rotate them 360° non stop so I could mount a spot light on my roof and rotate it from inside via rotor controller.

Took out the stop key. Like cutting off the stop horn on a servo. Gotta love our toys.

These motors have some real b@lls too. I used one to open and close driveway gates.

Sorry to be off topic. Have a great Thanks giving!

[aurbindnair]

why do you have to modify it. wouldn't it work with out one you know the fore legged 'walker' robot?

[Gelfling6]

Most servos are only 180-degree rotation. (0-180, 90 being centered.) These servos also make for a simple single-wire controllable (using Pulse-Width Modulation (PWM) output from a microcontroller.) drive motor that could be stopped, ramped from stop to forward, or ramped from stop to reverse, by changing the pulses to the signal wire. The gearbox also pre-made, so you already have a high torque drive, you simply connect the output to a wheel, or gear, and you're ready to move. Not everyone is making a walker robot. Wheeled robots are a little simpler, and don't require (a) multiple joints to move, (b) extensive code to move those joints in a logical pattern.

[creatorroboto]

I would just use a continuous rotation servo...much easier

[Gelfling6]

I think this is what the modder is trying to do.. There are other mods for converting 180-rotation servos to continuous rotation, simply removing the stop tab as this way shows, but replacing the potentiometer with a pair of 2.2K resistors wired in a "W" (or "M") to simulate the 5K potentiometer centered.

[scottsbots]

I've created a video of how to hack a servo on my site. Hopefully you find it useful.

http://www.scottsbots.com/videos.php

[bertus52x11]

I found an old comparable servo hack here on Instructables before seeing yours (sorry!). However, it is really old and the person does not seem to be very active anymore, hence my question to you.
Just not to flood this site with the same questions over again, here is the link: 

http://www.instructables.com/id/HiTec-Servo-Hack/?comments=all#C0MB712GJ289SX1

In brief, I'm looking for a servo that can be rotated more than 360 degrees, while maintaining it's accuracy. 

[azega]

I think what you want is a stepper motor.

[bertus52x11]

Can you control a stepper motor accurately? I mean, could I have it turn 425 degrees for example?

[azega]

Yes. Though you tell it to turn a specific number of steps which aren't exactly equal to degrees. For example a stepper I was using has 200 steps in one revolution, so 425 degrees would be 236.1 steps, but you can only move in whole steps so you would round it to 236 steps.

Here is a guide I did a while back that has a little more information.

Controlling a stepper motor with an arduino

[bertus52x11]

Thanks! That's great. I'll have to study it in more detail though. Can I contact you if I have more questions?
How is the size and the prize of a stepper motor compared to a servo?

[speeddemon974]

 thanks, it worked great!

[murugan]

hi i need one clarification from u  now i am converting servo motor into continuous  running motor futaba s3003 but i seen some sites they are removing the pot and inserting a 2.2 resisters i need why they  remove what is the function of pot in that circuit and tell me about the usage of 2.2 resestors also..

[azega]

Probably to trick the circuit into thinking it's never there. A servo uses the pot to know what angle it's pointing but by replacing it with a fixed resistor it would think it's always pointing in the same direction.

The reason I would think they would do this is so they could still use the circuit board to control the servo. You could could give it a signal to start rotating in either direction and it would just keep going until you told it to stop or reverse. You would tell it to stop by sending the signal that corresponds to the 2.2k? resistor (90 degrees?).

[tokomikon]

Nice info. That's help us to learn about motor servo.

Regards,
Dave T.
ATmega8535 | ATmega16 | ATmega32 | AVR USB ISP | Motor Servo Seller

[sdtacoma]

Thanks man! Worked like a charm. You got me worried about breaking the gear when I removed the plastic tab so I used a file.

[sirfag]

thanks for your help mate all i did was just cut the other wires and put the same wirs back on to it

[waSimon]

So easy and fast....
Thank you so much!!!!

[Mudbud]

 Thank you sooo much for this ible you made!!!!!!!!!! Its the answer to my problem! I am working on a robotic arm and I need it to be battery power and not those 1,2,3 ms pulses!  Thanks again!

[mrgreencool]

continuous rotation? is the rheostat in the servo can rotate 360 deg? i don't think soo..

[Nuno]

When what one really wants is just a motor with a gearbox, this modification is ok.

But you want a motor+gearbox+speed-control, then I prefer the modification below:

http://www.kronosrobotics.com/an116/GAN116_3003.htm

It's easier to do: no soldering iron and you only open one side. You don't waste the electronics. And you get electronic speed control. There's this video here that shows a minimal modification (no calibration after the servo is closed) but it's in a language most of you won't understand; nevertheless, it may help to understand the modification:

http://www.youtube.com/watch?v=VmLm1gl8glM

[mattbesquare]

Can I ask why you are removing the control board? Cant you take off the top cover and just cut the arm? I actually removed all the gears and just used the output shafts to power my model boats many years back (small scale).

[evildude321]

im gonna try this i want to make a winch for my t maxx truck

[kanamin]

a functional winch? like you really wanna pull your T-Maxx out of a bind with it? If so, then you should probably do this to one of those bigger 1/4 scale servos. Then again, if you remove the board you won't be able to control it normally by just plugging it in to the receiver, you'd probably need a separate ESC. if you just want it to be more "scale" and not be able to pull the T-Maxx you could probably just use a normal servo.

[dunnos]

ah i get it, is this doable with every servo? for example the cheapest one i can get through school (mom wont allow me to buy myself...sigh...)
servo ES-30 JR warning, dutch website youll get it anyway

Anyway, the basic idea is remove the tab that blocks it and the Circuit board? so then you just have a motor with a gearbox... genious

[amando96]

exactly... why buy a 15$+ servo when you can buy a normal DC motor with a gearbox... still the robot with this is awsome...

[robomaniac]

The answer is very simple, when I made that robot back in 2000, cheap plastic gear motors like Solarbotics GM2/GM8 did not exist!

[godfreyandthandi]

also to interface with robot controller boards you will need a motor controller board. a servo has a built in motor controller!

[monkeywithawrench]

yes, but he removed it

[emuman4evr]

couldn't you just put it back?

[amando96]

yes true, forgive me, i didnt know much back then... :)

[emuman4evr]

Is this servo good for modding to continuous rotation?
http://www.hobbypartz.com/kahaoubrmo14.html

[stevie1]

what exactly is the point of this anyways?

[robomaniac]

This instructable is part of the one motor walker.
http://www.instructables.com/id/How-to-build-the-one-motor-walker/

The point is to have a powerful motor to build all sort of project!

[mrthumbtack]

But isn't this motor not rated for continuous rotation? It seems like it would burn out much quicker now.

[viacin]

Doesn't someone sell a 360 degree servo? There's gotta be a ton of uses for one. If not, I think we found a new business :D

[Honus]

Here you go:
http://www.servocity.com/html/hsr-1425cr__continuous_rotatio.html