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Continuous rotating/normal servo - all in one

Rotates continuous or moves to desired position

This is a short tutorial how you get a servo for continuous running AND normal servo mode for a few bucks. You can switch between the modes in setting an additional pin high or low.

1) Open the servo and desolder the PCB. Remember the connections for motor and potentiometer

2) Remove the mechanical stop on the gear

3) Remove the potentiometer and modify it according to picture below. At least Hitec servos have this kind of potentiometer. Assemble the potentiometer and put it back on its original place

4) Prepare the servo as following

5) Make a small additional perfboard according to this circuit diagram and connect everything accordingly

I am using a TAKAMISAWA A5W-K PCB relay. They are very tiny, just like a 10 pin DIL chip and they are DIL socket compatible:

This is how my first prototype looked like:

6) You are done. Using a Sharp IR or ping on your servo, your robot can now not only look to the front, left and right, it can also look to the back!

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Anton has already done this;


Yes I know. And Anton has done this very nicely. But I want to expend as less effort as possible. My idea is to have a 4 wire servo. 3 wires as usual (GND/VCC/signal) and one wire to set the mode (continuous running/normal servo mode).

Best of luck :)

Well done =)

I want to preface my statement with the fact that I have as yet to produce any thing, at all.

arbarnhart mentioned in the shoutbox that it would be even better if the position the servo stopped in when switching from continuous rotation to standard servo. I suggested that if one would read the pot you could in fact do just that. I realize there is a lot more in the background that would have to occur as the pot adjusts from 0 to 5 or 10k, but, it should still be feasible. I also suggested that rather than utilize another pin the output pin that changes the direction could be used. It would need to be an analog pin though to read the pot position.

I do not mean to demean what Markus has done. There are lots of applications, most notably pistons and other eccentric mechanisms, where a position relative to the way the motor is mounted is always correct. But if it is driving a wheel on the ground, if I stop I really want to stop exactly where I am and be able to make adjustments relative to where I am.

It was suggested that I put my opinion, for what it is worth, in the comments and I decided to mention from where my opinion came.

I often come across as an old crank because I always want more features and it seems like nothing is ever good enough. What Markus did is quite good. When it was first posted, I had hopes it might do what I wanted, so I asked hoping there might be a good answer (I know there are ways to do it with the optics and marks on wheels or with the position sensor). I do appreciate the usefulness of what he did for a lot of applications.

I have seen these relatively new servos that have magnetic inductance sensors instead of the potentiometers. Supposedly when the servo is off it spins 360 degrees, so I was wondering, would it be hard to modd it (or it works this way out of the box?) to be controlable for complete 360 degrees position?

A great idea would be to have the servo with position control for 360 degrees working with pulses from say 1ms up to 2ms and rotate continuously one direction for a pulse less off 1ms and the other way for a pulse greater of 2ms, with adjustable speed for pulses between the position control and min and max pulse ranges (0.1 ms for min and 3 ms for max). 

Oh yeah, the links:



I don't think if the servo is off it spins 360 degrees. Otherwise this servo could not be used for air planes etc. Imagine the servo starting to rotate if you lose contact with the model.

Saw these servos: http://www.robotshop.com/world/specialty-servo-en.html

They have position, temperature, load, input voltage feedback, but the price...