Thread: 1 Encoder, 2 Jaguars
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Unread 02-28-2011, 10:56 AM
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Hugh Meyer Hugh Meyer is offline
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FRC #1741 (Red Alert Robotics)
Team Role: Mentor
  
Join Date: Feb 2009
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Location: Greenwood Indiana
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Re: 1 Encoder, 2 Jaguars
It seems noise into the Jaguars is causing the reset issue mentioned here and in another thread. When one connects an encoder or other circuit to the encoder input it works as an antenna to pick up noise.

So far I have found a 25 uf cap across the + 5 volt pin and the gnd pin on the encoder connector fixes it.

This may not work if all ground loop issues are not resolved. The opto isolators are needed to remove the ground loops and the filter cap is needed to filter the spikes created by the back emf when the motors stop or change direction.

We are using shielded wire with the shield grounded at the Jaguar and open at the custom circuit board where the opto isolators are located.

The only connections back to the Jaguars are from the output transistor in the opto isolator. I have seen some high frequency roll off and trouble with phase shift causing direction changes. I am still working this issue. If the noise is really fixed I might try to add another pull-up on the opto board to the +5 volts from the Jaguar.

Has anyone else seen these issues?

-Hugh
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