Servo motor driver

Hello Guys

For my stepper motors I use the A3967 easy driver and I m very happy. But now I have to control a servo motor with 7.4V voltage.

Are there drivers for servo motor and arduino ? Any suggestions please ?

Usually the driver is built into the servo (if you are talking about a hobby servo). All you need is to connect the control wire from the servo to an output and the servo and servo power supply grounds to Arduino ground. 7.4V may be too much for a servo. You can use a series diode or 2 to drop the voltage to where the servo likes. The Servo library makes control pretty easy.

yeap but what if the servo is of 7.4V fro max torque ?

If the servo is rated for 7.4V no problem. Hobby servos are usually 4.8 to 6V. Since I have no idea what servo you are using I wanted to cover the bases.

You have given us very little information about your servo. The term servo can refer to a wide range of motorized actuators. Help us out. Give us the data sheet, a link to the model of servo you have, or even just a picture.

For example lets say you have to drive this servo which max output is at 7.4V. Arduino output is 5V (and don't know about current of arduino output). How you will drive this servo for max power (7.4V) ?

You connect the servo POWER wire (usually red) to the 7.4V battery and you connect the servo SIGNAL wire (usually white or orange) to the Arduino output pin. Connect both grounds together.

The servo is controlled by a 5V signal and the current required is very low. The full servo current comes direct from the battery NOT through the Arduino.


So I just have to connect the servo power pins directly to the external power source and the data cable to arduino output without any intermediate componet (driver) right ?

Yes and connect all the grounds.

I would caution you to use some type of over current protection. I am in the middle of a project using the PowerHD HD-1235MG 7.4V servos. I had the power connected directly to a 7.4V Lipoly battery. A loose connector on a sensor caused the servos to jump back and forth just a couple of times while under a heavy load and 2 relatively expensive servos burned up. They are no longer responsive and upon opening one up, it had a strong burned electronics smell.

I'm not sure of the best way to protect the replacements. I now have an inline fuse on the supply line. I'm wondering if I need some other type of power regulation. Do normal RC servo controllers have some other type of power regulation? I know that the 7.4V lipoly battery really charges up to 8.4V. 7.4V is just the nominal voltage in the middle of the range. Is it a problem to run the 7.4V servo with a 8.4V supply? Do I need a step down UBEC or something to really regulate it to 7.4V or should the fuse be sufficient?

It may be simply that the load was TOO heavy. That's what burns out servos not just the availability of power.

Servo voltages have conventionally been given as the nominal voltage of a suitable battery, so 6V servos easily tolerate the 7.0+V of a fully charged 6V battery. So I'd expect a 7.4V servo to have no problem with a fully charged 2S lipo.