Trying to read current from the PDP

[Joe Ross]

Originally Posted by franktate

We're having a similar problem with three separate PDPs, all with firmware version 1.37. Even the RoboRIO web page Self Test for the PDP only shows all zeroes for all 16 channels. At firmware version 1.30, we were seeing values between 1 and 2 on all channels (even those with no breakers installed), but now it's just zeroes. Does anyone have any ideas?

How are you applying a load to the PDP channels?

[franktate]

We are running a motor at half speed through a Talon. And the motor runs fine.

[ozrien]

So just to be clear, the actual problem is that you're applying a load (robot is enabled and motor is spinning) and the reported current is zero. Is that true on all channels or just one? I mean if you move the load to another channel do you see the same problem.

The reason it was reading 1-2A before is because that is the raw output of the current-sense. It needs biasing (just like a gyro). The latest firmware zeroes it on boot (also like a gyro). But with either firmware, there should be a change in current, unless the current load is too small to measure. A free spinning motor with no load may draw 2A or less (which is in the noise floor). Remember this device is meant to handle/measure large loads (40A and up).

Are you using a Talon SR or SRX?

[Alan Anderson]

What kind of motor, and what is it driving?

[franktate]

It is a CIM motor driving nothing. So it could be that there's simply not enough draw to register, and I can believe that. I don't have access to it right now, but once I do, I'll put a load on the motor and also try moving the leads to a different channel.

Thanks a lot for the reply!

[franktate]

It does work now, mainly. Putting a load on the motor (with a finger) does get some different values returned. We just do still have some values coming from channels that aren't used. Oh well. This is just the test rig. Once we're on the robot, we'll be able to look at the data and throw out erroneous values (hopefully).

Thanks for your help.

Frank