Odd servo

Other Hardware Motors, Mechanics, Power and CNC
1

Hi, please forgive me if I post this in the wrong section as there isn't a section dedicated to servo.

I bought serval TowerPro MG 955 servos. It has this odd behavior, the the other servos I worked with, I can set the servo to a desired position, like this ServoN.write(90) for example, this set the servo to the 90 degrees fixed position. However, on the MG955, the servo will always go to 90 degrees than return itself to 0 as if there is loop go from 90 degrees to 0 degree even though in my loop() function I do not have anything looped. I am wonder if this is some kind of special purpose servo and how in the world do I make it to set to a fixed position? TIA.

2

Post your code, pictures and schematics - it will help us, help you.

3

rich1812:
the servo will always go to 90 degrees than return itself to 0

I don't understand your description.

As @crOsh has said, post your code.

...R

4

Most common servo behavior issues develop when trying to power the servo from the arduino. How is your servo powered?

5

TowerPro MG 955 servos

Most servos absolutely require an external 5v supply.

Those cheap TowerPro servos are are absolute rubbish!

I had to disassemble mine, resolder and reroute the wires to prevent shorting.
I Googled several user reports that the position pot used in the servo is very unreliable.

The MG 955 draws huge amounts of current sending huge positive and negative spikes through the position wire causing the Arduino to hang. (As seen on my oscilloscope)

I installed a 5.1v zener to crowbar the position wire.
To be safe I also added a 5.1v zener and a silicone diode in series to crowbar the external 5V supply to 5.7v

It is then reliable but untrustworthy.