how to route a DC motor power supply

[flote21]

Hello guys!

I need to supply a noise DC motor using +5v of my sensor board PCB. I am using GND plane and +5v plane to in the PCB and I am afraid that the noise effect of this motor affect to these power planes or other components of the sensor board.

My question is of anybody knows about pcb layout technique to isolated the signals of the motor and its power supply? Maybe should I use some kind of AO to isolate or any other idea?

Find attach a picture of the PCB.

 

[KlausST]

Hi,

i think the most prolem is the wiring, not the PCB.
All the current caused by motor and logic runs through one GND wire. It has an impedance, so every current cuses a voltage drop. Additionally every puls causes an even higher voltage drop.

So either use two seperate GND wires and two seperate 5V wires for Power and Logic respectively.
Or use differential signalling instead of single ended TTL wiring.

A relatively large ceramics capacitor next to motor connections may avoid high frequency components in motor current on PCB and wiring.

It depends on wire length, wire gauge, current value, current frequency....

Klaus

 

[flote21]

Do you mean a big ceramics cap between the power +5v and GND...

Anyway I would say that the only place where I can make improvements respecting noise removing is in the PCB sensorboard. There is not any possibility to do it close to the motor and also in the wires...

On the other hand i have been thinking to use optocoupler in power supply and TTL signal but I don't have the knowlodge to do it. Anyone has experience on this? Or maybe there is an application note where I can check this solution...

thanks,

Hi,

i think the most prolem is the wiring, not the PCB.
All the current caused by motor and logic runs through one GND wire. It has an impedance, so every current cuses a voltage drop. Additionally every puls causes an even higher voltage drop.

So either use two seperate GND wires and two seperate 5V wires for Power and Logic respectively.
Or use differential signalling instead of single ended TTL wiring.

A relatively large ceramics capacitor next to motor connections may avoid high frequency components in motor current on PCB and wiring.

It depends on wire length, wire gauge, current value, current frequency....

Klaus

 

[KlausST]

Hi,

ceramics capacitor next to motor connections

maybe dont go directely from the power planes to capacitor and motor connector, but use seperate wires from supply connector to motor. Then the motor current should not travel the power GND planes.
So you get a more clean GND plane.

I can´t see how an optocoupler could bring any improvement. This is often misunderstood. As long as motor current and logic signals share the same GND there is no benifit.
An optocoupler is good when you use two seperate power supplies and you need to send data from one power system to the other.

Is a serial data communication possible via RS485 or LVDS?

Klaus

 

[flote21]

No all the signals are single ended signals. There is not differencial signaling or RS comm....

mmm I see then I will try with the coupling caps....

Thanks!

Hi,

Is a serial data communication possible via RS485 or LVDS?

Klaus