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Unread 23-03-2015, 23:30
DougJensen DougJensen is offline
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Join Date: Jan 2010
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Location: Woodbury, MN
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Talon SRX limit switches - incorrect operation.

Background: Using SRXs with CAN. Updated with latest software (we have already been through (and won) one FRC competition, so yes they have been updated.)

Summary of problem:
Whenever the motor is traveling in 'direction A' and the 'direction B' limit is actuated the motor does not run at full power (it runs but at low power or with much 'stutter') - which is incorrect operation. Limit A should not affect operation in direction B and vice versa.

Using default Normally Open configuration (limit switch closes at limit.)
Using CTR cables and breakout boards.

More detail:
1.) The limit switches operate correctly in the 'appropriate' direction:
When the 'FWD' limit actuates, it stops the motor immediately when the motor is traveling in the forward direction AND the 'REV' limit stops the motor immediately when traveling in the REV direction.

BUT

2.) When 'coming off a limit', i.e. when the FWD limit is actuated but the motor is commanded at full power in the REV direction, the motor 'stutters' (it certainly does not drive with any appreciable power) until the FWD limit switch DE-actuates (the switch has some overtravel on it, so it remains actuated for some length of travel while the motor runs in the REV direction), but once the FWD switch is de-actuated the motor runs at full power in the REV direction as commanded. Likewise the opposite happens at the other end of travel. (The REV limit is actuated but the motor is commanded to full power in FWD direction - the motor does not run smoothly with any appreciable power until the REV limit de-actuates and the motor returns to full FWD power as commanded.)

As mentioned we are using normally open switches and have confirmed the operation manually (by shorting wires by hand.) Every time the motor is 'stopped' by either direction limit (by CLOSING) the corresponding limit switch (shorting the limit input to GND) the motor stops as it should, but the motor will not reverse gracefully when commanded - it stutters or runs at low power until the limit switch is OPENED.

Conclusion we reach: The limit switch for direction A is affecting operation of the motor in direction B, which it clearly should not.

Observations, suggestions welcome. Thanks!
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