Help on ground management on a micro servo conrolled system

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- Sink0
  
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posted
12 years ago

Mon, Mar 12, 2012 11:29 AM

Hi, i am building a small board to controll a micro servo using CAN. In order to make the sThe servo and the control system will have differnt power cables (sourced by the same battery). In order to make the system more organized, the board will have 2 connectors, one for the CAN incluiding the the control power rails, and anoter one for the servo powering. So at the board i wil have a third connector with the regulated servo VCC/GNS and the control signal. As i know the servo demands high peak current, i want to hava totally separated grounds at that board, with the connection between both at the battery. However my question regarding teh control signal. The battery will be about

1.5m from the control board + servo system, so there might be a ground potential difference, leading to a wrong servo signal reception. How can i solve that problem? Have a nice control signal , and do not inject power noise at my control board? Connect both grounds with a ferrite bead? Choke?

Thank you!

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- Tim Wescott
  
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posted
12 years ago

Mon, Mar 12, 2012 4:51 PM

If by "micro servo" you mean RC-style servos that run off of logic-level pulse widths, then they work OK in airplanes with wires that long.

If you mean you're going to cook up something on your own, or even for the micro-servos, why not bring the CAN cable all the way up to the mechanism? If you use the usual automotive CAN physical layer, it should be pretty resistant to common-mode noise, which means it'll work just fine.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

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