Does the cRio cut motors at 5.5Vdc on CAN?

[Mike9966]

Hi all,
I was just watching Al S's video on electrical design from 2009 and he mentioned that the cRio cuts the PWM outputs when the system voltage drops below 5.5Vdc.
Does anyone know if it will do this with the CAN control system too???

This seems like a handy feature.

Thanks much

Mike

[apalrd]

If the system voltage drops below 5.5v, the Jaguars might reset anyway. They won't be happy at least. I have no idea if the cRio does anything with the PWM's at this point. Unless the low voltage is resetting the cRio, this low voltage shutoff would not have an effect on the team-controlled Serial port of Ethernet port.

[Al Skierkiewicz]

Mike,
I was told that the Crio disables all outputs at 5.5 volts. That discussion took place at a time when CAN was not allowed. The reason for this is that the Crio power supply falls out of regulation at about 4.5 volts. This 5.5 volt trip is designed (as I understand it) to disable the robot before the Crio should/could reboot. Erik van Wyk I hope is watching and would have a more accurate answer.

[Mike9966]

Thanks for your thoughts Al.
I was showing the video to the kids last night as a refresher on things we want to plan in wiring.
The only way I can think of to discern this would be to put it on a variable power supply and decrease the voltage and see what happens......

We are a 2nd year team and are using 4 drive motors and so I'm more concerned about system voltage drop this year than last.

Well, if I get a chance to try it, I'll let you know.

Mike

[EricVanWyk]

The 5.5V number is only true for things controlled by the digital sidecar. I wasn't involved much in the development of CAN this year, so I am not sure of the behavior of CAN controlled Jaguars with Voltage dips. Hopefully Joe or TI will answer.

[dyanoshak]

Both Gray and Black Jaguars will indicate a Power Supply Under Voltage fault (slow blink red on the LED) when the power supply drops below 6V. The Jaguar is still on at this point, it just shuts off the motor outputs.

The Gray Jaguar will shut down completely after the voltage drops close to and below ~3.3V. The Black Jaguar will shut down completely after the voltage drops below 5.5V.

The time between a voltage fault and total shutdown can be quite fast, especially under sudden heavy loads.

If a Jaguar resets, all parameters will reset (control mode, trusted enabled, etc.). If the CRIO somehow managed to stay on while a Jaguar reset, it would have to reestablish a trusted link to the Jaguar and reset all the parameters. Joe might be able to chime in with a suggestion on how to deal with this particular situation.

-David