Drive a Sub-Micro Servo 3.7g (Generic) with 5V?

Robotics and electronics discussion Mechanical design and actuators
1

I note that the Sub-Micro Servo 3.7g (Generic) required a 4.8V power supply. I want to drive one from an Arduino, whicgh uses 5V. Will this be ok? If not, what sort of current draw can I expect? I would use a resister to drop the voltage from 5V to 4.8V.

2

Hello.

Well-regulated 5V is fine for a 4.8V servo, but the “well-regulated” part is not necessarily easy. Since these tiny servos don’t use much power, you should probably be fine with the Arduino’s 5V line.

By the way, a resistor is a terribly bad way to attempt changing the voltage from 5 to 4.8.

- Jan

3

Jan, I got the servo and tested with my Arduino. I wrote a small pgm to enter the angle from the serial monitor and use that to set the servo angle using servo.write (and echo’d it to make sure it was received correctly). 0-149 degrees works fine, but anything 150-180 degrees causes the servo to just spin around continuously. Any ideas what’s wrong?

thanks, Craig.

4

It sounds like you’re making a bunch of assumptions that aren’t necessarily valid. There’s nothing in the servo control protocol about “degrees”, and you shouldn’t expect servos to do more than about 150 degrees, either. Trying to command a servo past its mechanical limits is a good way to destroy a servo, so you should be very careful when you try to move past about 120 degrees of range, especially if you are not sure what is actually getting sent to the servo.

- Jan

5

I’m not sure what to make of this.
The Arduino Servo library says “Standard servos allow the shaft to be positioned at various angles, usually between 0 and 180 degrees”. The write() fn says “On a standard servo, this will set the angle of the shaft (in degrees), moving the shaft to that orientation”.
I guess i will just need to confirm everything by experimentation and not make any assumptions in future - thanks for the advice.

6

A lot of stuff out there for the Arduino is not very well done. I just started doing a series of articles on servos on my blog, but it might be a few weeks before the kind of info you need will be there. The list of servo limitations in the introductory post might be good to keep in mind.

- Jan