Spike Relays suddenly stop working

Hey all,

Quick troubleshooting question. We were using our demonstration time at a museum today. We launched a ball and suddenly four of our Spike relays went red non blinking. Because it was a demo and because we had to rebag we only did a cursory check. The bot still drives but those four no longer respond. Any ideas that we should check when we unbag at Bayou?

I would first check the digital side card and make sure it has all the voltage levels lights present. Then if that looks good check the ribbon / cable connection from the cRio to the digital side card.


The fact that they all did it at the same time makes me believe it’s an issue with one of the boards. I’d check the digital-sidecar to see if connections are bad, and potentially try a replacement if you can’t figure out. If not that, the digital card for your C-RIO, and if all else fails, your code or your C-RIO.

Things that rattle loose:

  • Check the three Digital sidecar (DSC) power lights are on and bright green.

  • Check the ribbon cable hasn’t loosened and is well and firmly seated at both ends.

  • Check that the Digital Module is well seated in the cRIO chassis.

  • Check that the DSC Relay lights come on when the code orders them to.
    *]Check the Spike end of the PWM cable with a multi-meter to see that you’re getting ~4.9v between the ground and the red wire (if the red DSC Relay led is lit), or the white wire (if the green led is lit).
    Digital sidecar could have metal shavings inside, but you’d have to remove to open, clean and inspect for internal damage.

This leads me to an interesting question. If you break something (electrical or otherwise), can you fix it during unbag time for a demo?

Is your RSL working? We had our RSL and compressor drop out during competition this past weekend. RSL was dead and compressor relay (only relay we use) was red/orange and non blinking. None of the lights along the relay outputs on the Sidecar were working. We swapped the sidecar after running one match with no air and everything was back online. All PWM outputs were functional with the defective sidecar, only relay and RSL light showed problems. We did have some funkiness going on with our limit switches but they were never directly linked to the sidecar. All issues did disappear after the swap though. One of the FTSs had mentioned that they had an issue where bad RSL lights were causing a certain chip on the sidecar to fail and consequently take out the relay outputs. This was not the case for us (blown C6 capacitor) but had cost one team 4 sidecars that competition.

No working on the robot.
If it’s broken in the bag, then your demo will have to be a static display.

What if you break something during the demo, that wasn’t broken in the bag.

No still means no.

My thought is that it’s a problem with the ribbon cable, the DSC, or the DSC power.

Not to derail the thread even more, but, IMO, testing, during a demo, a robot to see what breaks, then planning how to fix it is an advantage gained by giving demonstations. While I do agree what MysterE did was not against the rules at all, he still gained an advantage over a team that did not do a demonstration. Fining, diagnosing, then fixing this problem at competition would have been more difficult.

There is a small difference in color on the Spike so you need to be sure when you start your troubleshooting process. An orange LED means the Spike is not enabled or connected. A red LED means it is commanded to one state while a green indicates the other state. To be sure, just look at the DSC next to the connectors for the relays. If any LEDs are illuminated on the DSC, they mimic the command sent to the relay outputs. No LEDs on there means the relays are not commanded to switch. Often the cable linking the DSC to the cRio digital module came loose. I had two teams with that issue over the past weekend alone. Another issue is metallic debris working it’s way down into the DSC. This can manifest as a variety of issues most often damaging the DSC. Please ask your LRI at Bayou for assitance and he will help you check through the list. Don’t wait, early on practice day is a quiet time for him.

Hey all -

Thanks so much for your replies - I have forwarded your comments on to my build team for later.

Also - I do agree that the demo did provide one advantage. It broke there instead of at the competition field. But what I do have to say is that the advantages of that are only insomuch as giving us a ‘heads up’ for competition.

The biggest thing for me is that any team at any point has the ability to do a demonstration. The ‘advantages’ are muted by the fact that every team can do a demo during this period. TBH, I would love it if every team would. Can you imagine if thousands of FRC teams took one day between build and competition to show off their robot - regardless of if it revealed a flaw in their design?

Thanks again, everyone!

Not quite the one day thousands of robot demo but we just were part of a week long promotion/fundraising event.

McDonald’s Restaurants of Hawaii held a fundraising event for Hawaii FIRST teams. Across the state between Mar 17-23 local FRC teams held robotic demos at their local McDonald’s. Most of the demos were held on the weekend of the 23rd.


There were potentially 29 teams showing off their robots over that week. We were unable to show off our competition robot since it was already crated and on the boat to the HI regional. We did bring our practice robot as well as a few of our Vex bots. An excellent time was had by all. We had great interaction with the community handing out information as well as several different coloring books we make for the kids. And perhaps some possible recruitment of future technology leaders happening…

This very gracious donation resulted in over 40k dollars. Every local FIRST team receiving about $1300.

This really was a great fusion of local sponsorship and community spotlighting of educational robotics.

McDonald’s of Hawaii also announced an additional 1000 to each Hawaii team traveling to the world championships…

“I’m lovin’ it!”

Mahalos to McDonalds and Friends of Hawaii Robotics. Without your hard work and support there would be far fewer FIRST teams in Hawaii.


If it’s something small that doesn’t require special tools, more than a couple minutes, or any large replacement parts it should be fine.

Example 1: Wire becomes unplugged or broken and can be replaced in a minute or so. Yeah, I would think so.

Example 2: Mechanism breaks and falls off robot (pretty small), but a replacement is lying around on display and can be swapped out in a minute or so. Probably. On the border of no.

Example 3: Mechanism breaks and falls off robot (it’s like 10 pounds), but a replacement is lying around on display and can be swapped out in a minute or so. Nope. That robot is broken until you unbag it at an event.

Example 4: Wire and custom circuit becomes fried and requires a good hour of rewiring and soldering to a PCB. Nope. Prepare spare to bring, but can’t be fixed today.

*Just my opinion.

It would be the same as if you broke something without opening the bag. I know of at least one team who noticed after they sealed their bag that their tools were still in the robot. I seem to remember at least several wrenches and a multimeter.