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Unread 08-02-2011, 11:21
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Re: Why are Limit Switches outlawed with PWM, but not CAN?

Al,

That doesn't seem right.

When using PWM, the only action of the N/C limit switch is to STOP the currently commanded PWM action if the limit circuit goes open. If the limit circuit is closed, the normal PWM command is in effect. This PWM is still fully under cRIO and FMS control. All the normal watchdog, comms, FMS safety protocols are still in full effect.

We know this because the two Jag jumpers that are normally installed just act as limit switches that never go open.

How can connecting N/C switches to these (which can only STOP the motors) create safety issues?

Phil.

Quote:
Originally Posted by Al Skierkiewicz View Post
Phil,
Under CAN the state of the limit switch must be read by the Crio and then a motor command is issued if the FMS is still allowing active motion. The limit switch in PWM mode controls the Jaguar directly, independent of the the Crio, and therefore, will continue to run the motor without interaction with FMS. Motion must stop under control of the FMS for either match play or safety disablement.
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