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Splitting encoder signal

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Some times it is necessary to feed encoder signal of motor to two devices: to drive and the motion controller (such as Mesa card in LinuxCNC installation). In such case, the safest way is to use optoisolators to provide second encoder output that is galvanically isolated from the original signal.

Encodersplitter.png

Splitting encoder signals with isolation. 5V-ISOLATED should be connected to motion controller's 5V supply (powering the optoisolators). Note: if long cables used (>3m), then termination of encoder differential pairs (A+ to A- etc) may be necessary with 120 ohm resistors at the drive/controller end.

Suggested part types for isolation are:

  • Optoisolators: H11L1 (support frequency up to 500 kHz)
  • Resistors: 1 kOhm
  • Capacitor (for opto 5V supply): 100nF 25V ceramic. Optionally also 10-100uF electrolytic in parallel.
Encodersplitternoniso.png

Splitting encoder signals without isolation. Note: if long cables used (>3m), then termination of encoder differential pairs (A+ to A- etc) may be necessary with 120 ohm resistors at the drive/controller end.


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