limit switch

[wedellm]

Are we able to wire a limit switch between the 884 and the motor?

[tbmantia]

I would assume that you are doing this to affect the power on the motor, in this case the answer would be no you cannot do this. See rule R62 & R63.

[Alan Anderson]

Meddling with the motor power directly is against the rules. You'll have to connect the switch to a digital input on the Robot Controller and use software to turn off the pwm output to the Victor when the switch is activated.

[purduephotog]

Originally Posted by Alan Anderson

Meddling with the motor power directly is against the rules. You'll have to connect the switch to a digital input on the Robot Controller and use software to turn off the pwm output to the Victor when the switch is activated.

It's a pity, really. I wouldn't mind having a 'hard' emergency switch that would disengage the motor should our arm extend past the end. My fear, perhaps ungrounded, is that a failure in software will allow a failure in hardware. I've seen too many test stands destroy themselves because the motors were instructed to go when the hardware was maxed out.

Test, test, test again

[Al Skierkiewicz]

From the Robot Rules Rev F In part...
<R61> ...
Custom circuit outputs can not connect to speed controllers, relay modules, or pneumatic valves....

<R62> Inputs to custom circuits can be connected to the following sources:
• Speed controller or relay module outputs
• PWM, relay or digital outputs on Robot Controller...

<R63> Custom Circuits can not:
• Directly alter the power pathways between the battery, fuse blocks, speed controllers, relays, or motors. Custom high impedance voltage monitoring or low impedance current monitoring circuitry connected to the ROBOT’S electrical system is acceptable, because the effect on the ROBOT outputs should be inconsequential.
• Directly affect any output devices on the ROBOT, such as by providing power directly to a motor, supplying a PWM signal to a speed controller or supplying a control signal to a relay module.

In effect, the answer is No you can't connect the switch to the output of a speed controller. If you are using this to limit the motion of an actuator, it is easily handled in software. You may wire two switches to a single input if you have a need for two limit conditions. i.e. full up or full down on an elevator.