Intermittent Loss of Communications During Play

[Mike Betts]

Symptom:
Robot loses communication momentarily after impact with another robot or with field element.

Disclaimer:
As with any real life, non-trivial issue, this is likely a multi-problem problem and the solution described may not mitigate all instances.

Discussion:
I was a robot inspector at the Florida Regional last weekend. There were numerous complaints of momentary loss of communications but no single clearing house to vet all problems… I helped quite a few teams and came to the conclusion that no robot which used the power supply cable which came with the DAP-1522 radio had this issue. In fact, while working with one team, we succeeded in getting the DAP to be completely unpowered even though it appeared securely plugged in. We were able to restore power to the DAP by touching the power connector ever so slightly (virtually a feather’s touch).

All of the teams that I assisted which were experiencing problems were using the power connector from last year’s robot or a connector that “seemed like it fit” from Radio Shack.

It is my (largely subjective) conclusion/theory/assumption that the barrel accepting the male pin in the connector is a few mils smaller on the DAP’s BOM connector than on the connectors giving is trouble. Also, the momentary loss of power to the DAP is just enough to corrupt its driver and/or firmware circuitry but not enough to force its CPU into a reboot condition.

Solution:

• Find the AC power supply cord that came with the DAP-1522 and cut it in half.
• Note that the wire has two conductors. The positive conductor is identified by a white stripe printed on the black insulation.
• Install .250 spade disconnects on both ends so that you can revert to using the cable as an AC source in the future.
• Now store the half connected to the AC power supply away for future use and wire the other half into your robot. Note that the white stripe conductor gets connected to the yellow lead of the 360-CPR.

Identification:
The power connector which came with the DAP is a molded plastic, right angle connector whereas last year’s connector was an axial leaded barrel connector.

Epilogue:
I strongly suggest that you at least pack the DAP-1522 power supply cable with your spares before departing to your competition. In that way it will be available if you encounter this problem.

Regards,

Mike