View Full Version : Parallax Servo to handle bigger motor.

09-04-2006, 07:23 PM
Hi all.

I'am doing some experiment with robotic. I need some bigger servo for precise movement.
I·have Parallax Servo with me and try to modified the Servo by changing the motor(6 Volt)

It's work but the problem is one of the IC on the circuit become hot in just less than two minutes.
I worried this will damage the circuit.

Anybody know how to solve this?

Please Help!!!!

09-04-2006, 07:59 PM
Your new motor is drawing to much current. The Parallax Servo can work off 4.8-6 volt as it is, there is not need to modify it.


Russ Ferguson
09-04-2006, 09:03 PM
I think that the motor you are using is drawing to much current. I would look for a motor that draws 0.5amp or less. Use a meter to measure the current (though I would hope that you had a pretty good guess as to what the current was going to be to begin with - else you might blow a fuse in your meter).

Gearmotors like this one from BGMicro do not draw much more current than the motor that is in a regular servo. And they·provide alot more power and/or speed.


I have a board that I pulled from inside a Parallax Continueous servo and connected to it. It seems to handle it OK without getting hot.

BGMicro carries three or four different gear ratios of the GM pictured. Pick the gear ratio that meets your needs.

One of the·Solarbotics GM products should work good with a salvaged servo controller also.


Post Edited (Russ Ferguson) : 9/4/2006 2:12:13 PM GMT

09-05-2006, 08:42 AM
Thanks to crgwbr (http://forums.parallax.com/member.php?u=46269)·& Russ Ferguson (http://forums.parallax.com/member.php?u=40662)·for your reply.

What I'm trying to do is to modified my toy robot. I want to take out the controller

and replace it with my BOE without taking replacing the motor. Is there anythig esle

I can do to cut the drawback current from the motor?

Russ Ferguson
09-05-2006, 09:41 AM
Seems to me that you need a circuit that amplifies the current from the salvaged servo controller board. I have not seen a cheap module or kit version of this kind of thing.

Perhaps you will need to get a servo controller board that is rated for higher currents. You might as well spend your money on something that is designed for higher currents rather than trying to beef up a servo controller board that is salvaged out of a $7 servo.

The Motor Mind B may do the job for you if·have a·small toy RC car. http://www.parallax.com/detail.asp?product_id=27961

The SOLARBOTICS H-Bridge kit could be used if you had enough electronics back ground to implement some logic between the salvaged servo controller motor output and this H-Bridge. http://www.solarbotics.com/products/index.php?scdfa-250100084-viewDetail-productzq3965zq4categoryzq31=true

It may be possible for you to use the H-Bridge that was on the toy car's circuit board. If you can figure this out then you·may·also be able to figure out how to biuld the necessary logic to go from the servo controller motor outputs to drive this higher current H-Bridge.

If·you have a·large RC car with a BIG·hobby store·motor in it, then you will·probably need·to start saving your money for a pair of the HB-25 controllers. http://www.parallax.com/detail.asp?product_id=29144

The "Electronic Speed Controller" is also a possibility. See the thread - "Electronic speed control + BS2". http://forums.parallax.com/showthread.php?p=600278

Post Edited (Russ Ferguson) : 9/5/2006 2:55:57 AM GMT