ATOM Motion, if DC Motor is running- disturbance on Servo I2C Interface

HARRY_GO

Hi to everybody,
as a new user of ATOM Motion I have a problem when running a DC motor (on of the 2 DC Motor interfaces) and havin a servo at one of the servo interfaces (4x I2C Interfaces). As soon as i start the motor, the servo starts to tremble-moves quickly some degrees forward/backward. If i stop the motor, the servo stops trembling. (Even disturbance at the PC screen visible)
I tryed it with different motors, always the same.
I put some catacitor paralle to the motor power supply, servo stops trembling.

How can this be, i buy a board, designed to run 2x DC motors and 4x Servo and there is a disturbance between them????

Does anybody have the same experiance?

Thanks for the information

HARRY_GO

Seems to be EMC disturbance.
Whenever the DC motor is running, the Servo jumps back and forward , the IT remote control does not work...
Motor stop, everything is fine.

So i tried some things and found out:
Usually the DC Moto cable leaves the Atom Motion case in a 90 degree angle. If i bend the cable right after the plug, so that tha cable moves parallel away from the atom motion case, everything is fine.

Seems to be a disturbance due to the PWM which disturbes even the power supply. Thats why servo and IR sensor gets crazy.

As my teachers always said, EMC is magic.......

If you have similar experiance, please answer..

thanks
Harry

holofloh

It might be the PWM that makes problem but often its the brushes in the motor that causes the disturbance (sparks during operation). Test if you still have the problem with a resistor instead of the motor. If the problem is gone with resistor then it's the motor. And YES, this is a EMC issue.
Try some filtering on your DC motor by adding 100nF capacitors on it. That means from DC+ to motor case and from DC- to motor case (known as Y configuration). Very important: As close as possible to the motor with leads as short as possible! Solder them direct on the motor. If this not help add another 100nF between + and - (known as X configuration) and also a inductivity of a few µH in the DC+ and DC- wire (this can be a wire that goes a few times trough a small ferrite torroid).

Edit:
"As my teachers always said, EMC is magic......."
-> capacitors and inductors are the magic spells!