Re: COMM lost way to many times
 

hot glue where?

Re: COMM lost way to many times
 

ya but the robot is in the bag

Re: COMM lost way to many times
 

we have all kinds of batteries but we lost comms some times when we were just going under the low bar. No big current draws, no big bumps.

Re: COMM lost way to many times
 

We had some issues with our radio and/or FMS at the Tech Valley Regional this weekend.

One of them was on us (tug test failed on our radio power connector), the other was indeterminate. (CSA/FTA was blaming robot power, as a whole, but we have video showing no power loss on the RoboRio.)

Regardless of what the problem is, even as a rookie team, the instrumentation provided by the RoboRIO/PDU/FMS/DS completely fails during problem events.

During the aftermath of our issues, we attempted to use the DS logs to trace voltage, power draw, comms, and log messages from the RoboRIO. The problem is, you can make "guesses" about your voltage state in the fraction of a second leading up to the event, but once it happens, you're blind.

We're already redoing our robot code library for next year to address some of these shortcomings. We'll be logging voltage and PDU stats, as well as bridge/radio and FMS connectivity via ethernet directly on the RoboRIO. In addition we'll be using a cached-logger, such that if DS communication is lost we can back-fill in our logs.

We are attempting to address the issue of the complete lack of FMS logging, and the logging dropout during any communication loss event. We're also pushing the logging closer to the source of the data. Our goal is to be able to document the voltages, RoboRIO, PDU, and Radio/FMS/DS status in an effort to diagnose issues.

Re: COMM lost way to many times
 

Do a pull test on all wiring connections. That means where a wire goes into a Weidmuller or Wago connector, where a wire goes into a crimp lug, where a wire goes into an Anderson connector and where the wires go into the plug for the RoboRio power. If wire slips out, re-do the connection.

Check all screw/lug connections such as the battery cables on the battery and on your main breaker. The wire and lug should not be able to rotate relative to the battery or breaker. Tighten the screws if they move.

Use a flashlight and examine closely where the wires go into the small Weidmuller connectors (i.e. RoboRio power on your PDP). Look for stray strands on any wire that is not in the connector. These stray strands can touch adjacent wires which is always the opposite polarity on the PDP, VRM and PCM. If necessary, cut off the "crinkly" stripped ends, strip to the length shown in the Users Manual for the PDP, VRM and PCM, twist the exposed strands so they lay neatly together then re-insert the wire in the Wiedmuller connector carefully and ensuring that ALL the strands go in.

Re: COMM lost way to many times
 

What in the video establishes that there was no power loss on the RoboRIO? If you're just looking at the Robot Signal Light, it's possible that your RoboRIO browned out due to power loss, but didn't completely shut off.

Re: COMM lost way to many times
 

We solder and heat shrink where we can, and hot glue everywhere else. So the connections to the Voltage Regulator are all hot glued. We were seeing all sorts of radio drops out just as you've described on both our comp and practice bots. Since hot gluing the radio wires into the voltage regulator we haven't lost comms. (~19 matches).

We use hot glue on nearly every connection, including our encoder cables, limit switches, arduino plugs, etc.

If you want something less permanent electrical tape tends to work well enough, but I haven't seen anything better than hot glue this year.

Re: COMM lost way to many times
 

So everyone knows, the DS logs are able to tell you if the roboRIO rebooted.

When a connection is established between the roboRIO and the DS the roboRIO will send a message saying how many seconds have passed since it last booted up, the DS then stores this information in the log. Look at the messages when communication is reestablished to find this information.

Re: COMM lost way to many times
 

Why is everyone missing the obvious solution? Use passive Power Over Ethernet (POE) on the port that supports it. The Ethernet connector snaps firmly into place. I've never seen one come loose due to bounces or vibration this year.


On the other hand, more than half the robots I checked had loose terminals either on the battery or the main circuit breaker. All of the "lost communication" events I followed up on at both of the events I worked at were associated with a faulty power connection. All.

(I'm counting only ones where there was actually a loss of communication, not the few the drivers called "lost comm" but where the problem was that robot code crashed or a joystick came disconnected or the Driver Station was being interfered with by a software update process.)

Re: COMM lost way to many times
 

I'm not familiar enough with PoE to be comfortable without some details. I sure don't want to fry a radio. With a quick search I haven't found out the best way to wire a PoE for this this radio. I assume you can use the 12 v port on the VRM into a spliced ethernet cable but what pins are used and which port does it go into in the router. I apologize if this has already been discussed. I didn't see it in my searching, but might have been looking for the wrong things.

Re: COMM lost way to many times
 

FIRST should consider allowing the use of a small secondary battery to power the radio should it lose connection with the VRM/PDP. The battery would be used exclusively for the radio and prevent any reboots due to power loss or brownouts elsewhere on the bot.
Consider that batteries and the PDP are generally well-hidden on the bot (the battery to lower CG and the PDP to shorten total wire lengths. However the radio needs good clearance from metal and motors to ensure a solid RF connection, leading to longer wires and generally less secure mounting (subject to more vibrations potentially). This all introduces risk of wire/connector failure. Allowing a small battery placed alongside the radio as a parallel backup would be beneficial.

Re: COMM lost way to many times
 

All the information I needed I found through the OpenMesh web site and a simple search for "passive POE". I summarized it here.

Re: COMM lost way to many times
 

Hot glue at the connection between the power plug and the radio.

I was the mentor from 379 that was trying to help. At the time we probably couldn't wait for a hot glue gun to heat up We reset all wires at the VRM. Checked other connections, inspected contacts, and zip tied the battery connection. Not knowing the robot, it was hard to inspect.

I do feel that it's something dealing with an electrical connection. Try replacing the Anderson battery/PDB connection, wire and all, from the robot. I wish we could have figured it out, you guys have a great design, good luck this season.

Re: COMM lost way to many times
 

Which port on the radio supports POE?

Re: COMM lost way to many times
 

I highly recommend against hot gluing the plug into the radio (and I also advocate against hot gluing or taping ethernet cables and power cables pretty much anywhere). It makes replacing those wires later more difficult.

The radio's plug is particularly problematic with hot glue. You can no longer easily detach the radio from your robot to program it at events, and swapping out radios should yours need to be replaced for any reason suddenly becomes much more difficult.

Furthermore, the issues I have seen are generally not that this plug comes loose. The problems are generally that the wires going into the Weidmuller connections on the VRM have too much copper showing and are shorting out, or that there are loose wires elsewhere in the chain.

I had a team that had mummified their Ethernet ports on both the radio and roborRIO along with the USB cables going into the roboRIO and the power plug on the radio with electrical tape drop out during a match. Seriously, there was a large mound of the stuff over everything. They asked me if I thought they should add more electrical tape since they were still dropping out. At that point I demonstrated that the wires going to their radio were just falling out of the VRM with very little effort on my part.

Understand the problem before trying to apply bandaids. You might not even be putting the bandaids in the right spot.