Servo moves on powerup?

Hi, I am using the 8 servo controller. When I power it up, the servo moves ~20 degrees relative to the original position, always in the same direction. It is not moving to the neutral position… Why does it do this? Could it be a power problem? I am using a 5volt supply with the Vcc=Vs jumper.

Another weird thing, in 8bit mode, commanding 140 and 160 move to the same position…
0x80 0x1 0x3 0x7 0x1 0xc
0x80 0x1 0x3 0x7 0x1 0x20
go to the same angle, but other positions around 160 are continuous. If I command 158, 159,160, 161 it will jump down to 140 and then back up to 161.
This is probably just a bug in my code.



Your problem most likely stems from power trouble due to your using the Vcc=Vs jumper. Are you sure your power supply can deliver the current the servos need while staying in spec? What happens when you don’t use that jumper and use separate power supplies?

- Jan

sorry, I guess this is just a servo question, its not an issue with the board. Is it normal that the servo moves when I connect power to it? I have it powered independently of the board and it always rotates 20 degrees on power-up. This is just annoying if you want the position to stay the same through a power cycle.



Most servos will twitch when you apply power to them. 20 degrees seems like quite a bit to me; I suspect that different servos will move different amounts.

- Jan