Blown talon srx modules

[GregGarner]

During all the previous failures the Talon SRX modules were not warm at all. They were essentially at room temperature. We haven't noticed the Talon SRX modules getting warm even under fairly heavy loading. I attribute this to the extremely low on resistance of the H-Bridge inside the Talon, just not much power dissipation there. We also have the Talon's mounted to aluminum to keep them cool.

We are quite sure that the cables have no internal shorts or other faults, because we haven't replaced the cables and the replacement Talons connected to those cable are working properly.

I did hook up the scope last night, and I found that there is a large transient on the 3.3V wire at the Talon SRX. In particular, I do see large transients on the 3.3V line when running the motor, but I see no such transients when moving the motor manually. I think this is strong evidence that the 3.3V wire in our cable is coupling in noise from the motor wires. Again, we are possibly the only team making our own custom ribbon cables, so it is likely that most other teams aren't seeing this problem because they didn't run the 3.3V signal out to the end of a 8 foot cable in parallel with the motor wires.

I briefly looked at the 5V line and the transients seemed much lower, perhaps because there is a load on the 5V line in the form of the encoder.

Therefore we will now proceed to reworking the cables as previously described. I am hopeful that this will solve the problem. The breakout boards from CrossTheRoadElectronics just arrived (Thanks Mike!), so I should be able to get the team to make progress on this change tonight.

Thanks to everyone who is trying to help us solve this problem!

Here is the highest transient I saw on the 3.3V line at the Talon connector while running the motor. I think the peak voltage was probably around +-7V:


GregGarner
FRC GearHogs 3612