Servo Issue - Working with Some and Not Others

Hi there!

I am using the arduino example "sweep" servo program to control a Tower Pro Micro Servo - SG90 (9g), and it works fine. However, I have recently purchased two Tower Pro MG995s and when I plug in the same three wires into the tower pro header, the servo is all over the place, with no recognisable pattern. The same happens with both the MG995s, but then when I return the pins to the SG90, it works fine again.

I am using Arduino Uno Rev 3 and the arduino servo library and an external 5v power supply if any of that has any relevance!

Any help on what the problem could be would be much appreciated. Thanks in advance! :D ;D

Let's see a schematic. Got the grounds hooked together? (I guess so or nothing would work, but let's see the circuit.)

If you have an external power supply separate from the arduino, then make sure you have a good ground between the external power ground and the arduino ground.

Yes the grounds are solid, and if they weren't, then why would it work with my smaller servo? ;)

benstobbs: Yes the grounds are solid, and if they weren't, then why would it work with my smaller servo? ;)

It might not be 100% and be ok for low current?

Post a schematic else we're all pissing in the dark, here.

benstobbs: Yes the grounds are solid, and if they weren't, then why would it work with my smaller servo? ;)

If your wiring is correct, then your 5v power supply may be adequate for the small 9g servo, but is probably inadequate for the big MG995 servo.

The bigger servo need several amps to work at all - I'd estimate about 2.5A min from the specs. Your supply is failing with the high power servo but not the lower power one.

Approx 90% of servo problems on these forums are inadequate powering.