Failure of Robot Interface

[David Brinza]

Originally posted by Kojib
In order to keep this from happening in the future, could I simply either get some foam or rubber gromets to act as shock absorbers between the radio controller and the frame of the robot? If you respond to my question, please explain as much as you can, either what actually happened or what might fix it in the future. Thanks

Placing rubber grommets, foam or even balsa wood between the radio controller and the frame will certainly help reduce mechanical shock transmitted from an impact to the internal components of the radio controller. Severe mechanical shocks can break fuses, wires, capacitors, resistors or crack solder joints. The latter case (cracked solder joints) is often intermittent in nature - which can be really difficult to diagnose. Sometimes tapping on the controller may re-establish the contact, but it doesn't fix the problem. Tapping on it more may cause it to fail again.

If you observe this intermittent behavior, get a replacement controller and don't hard mount it to the frame. A thin piece of balsa wood or foam between the controller or frame can help reduce the mechanical shock experienced by the unit considerably.

Good luck, and see you in Houston!

[Kevin A]

our robot controller is strong enough to take some good drops in the build season. It lasted through the shorting of the ower wires to the GYRO. And as for the radio on the robot...it met the midfield barrier and lives to this day.


Kevin Antaki
Team 481

IM Me: xpalendocious

[Al Skierkiewicz]

There are a lot of questions above me here so let me try a few...
In St. Louis (I was just visiting) there was one player station that had a lot of failures. I think it was the right side Red. From Friday PM to Sat AM I think at least 5 or more teams went dead at that station. So I don't think anyone had hardware failures at that point.
When tethered there is a strict limit of 25 ft with known good serial cable, if you have that really thin stuff and/or have lights on your button box, the current draw through the cable is high enough to cause a brownout at the OI and it won't operate. (That is why local power brought it back in the one case above.)
Generally, the Innovation First stuff is pretty well put together and should survive any shocks we can give it. The RC has a few failure points, one being the connectors can't take side loads. If you don't tie down all cables entering the RC you are asking for trouble. Another is the Pico fuses are not tied down. Many teams put a piece of tape across the top to hold them in, but there usually isn't much of a problem. I have seen a few teams this year who mount the RC upside down, which gets gravity working to drop the fuses out.
Beyond that you should check for crimped or severely bent cables. (look for someone who get very aggressive with a tie wrap as the cable goes around a corner.) Sharp bends and crimps on the radio cable especially, spell disaster.

[KenWittlief]

if you cant use the tether cable, check the pins on the OI and the cable - you might have bent a pin - very easy to do.

[Adam Y.]

We tested the robot after the match and it was fine. Next match, our robot ran perfectly without any changes except changing a constant for amount of turn in autonomous. That weird and it did not seem at all our fault that nothing worked.

I'd hate to tell you but it probably was your programming that was at fault. I know our team had a problem when they downloaded the program into the robot it just stopped working flat out.

Although it is claimed that there is no interference when this would occur, I am not yet convinced that some interference might be possible. It might not be data but it might be RF intermod. We are still looking into this and will pursue it with Innovation First in two weeks

Innovation First would know if there was interference during a match. I saw the device they use to check for it at one regional.

[Al Skierkiewicz]

Innovation First does not carry all their test equipment to all competitions. Coming from an RF background, I begin to suspect anything from the presence of more than one transceiver pair. We are so sure of problems that there is a prediction software package to predict the interference caused by wireless mics on each other. The mixing of two frequencies coming out on a third frequency is quite common. Even the movement of conductive metals withing a few feet of the transmitter can cause interference on the received signal.

[mjt902]

HAVE WE EVER!!!

responding to the original post: our tether cable failed us in the finals, even though it appeared to have sustained no damage. i jumped up and down and the 'head ref' guy told me to calm down. it was sweet... well not realy cuz we lost.

[Specialagentjim]

Team 108 had a similiar problem at both UCF and the Chicago Midwest Regional.

We experienced problems on practice days in which the robot would not turn on when the match began. It was mostly seen on, I believe, the blue alliance station at Chicago, and not just by our team. FIRST insisted that it was something like a dead serial cable, and that they had "had a lot of those happen today"....Seems kinda odd...my cables don't generally up and die outta nowhere..

[mjt902]

well, it happened to us too. i got a funny side story to tell ya too- i tried to thank the head ref guy for his attempt to get to the bottom of the problem with us after we had DEFINATELY lost the finals. about a minute later i was like 'oh shoot, he prolly thought i was being sarcastic' and so i went and apologized for maybe appearing to be sarcastic. anywayzz, i don't see how any team could expect or even suspect a serial wire to go dead, so lets just look at it and say, 'its for the best' even when it happens in the finals, and most importantly 'it happened because the robot was tired of moving.'