Robot Controller Interference?
 

We are having problems with "No Data" cutouts with the O/I while in our lab. This problem does not occur when outside the room, only inside. It happens with all the O/I and the Robot Controllers we have, including our new EDU robot controller.

We have an Apple Computer "Airport" in the room, but the problems exist when all computers and the "BaseStation" are off and unplugged. Besides, I think the Airport is in the 2.5 GHz range. I don't know what else could cause this interference.

The interference seems pretty consistant, resulting in a "No Data" cutout every second or two.

HELP??

-Mr. Van
Coach, Team 599
CSUN/Granada Hills High School

The radios are 900Mhz. Cordless phones, pehaps? Large motors nearby? High-voltage power?

Does the distance between the OI and RC radios matter? If you put them mere inches apart, do you get a signal?

Mere inches... still get "No Data" drops.

No cordless phones in use nearby as far as I know.

-Mr. Van

What kind of materials are the walls and ceiling made of?

Try changing the channel on you OI ... that's what we have to do.

Is anyone using a cell phone or two-way radio? That screws us up sometimes.

I know this is common sense, but make sure your robot battery is charged! If you're using a battery to power your controls, make sure that is fully charged :)

- Katie

fully charged battery. Walls made of wood/stucco. It is possible that we have 2-way radio in opperation here - the campus security people use them, but the problem doesn't seem to happen outdoors.

-Mr. Van

I made a quick search and I found out that stucco walls can prevent radio transmissions from reaching the source. Along with the campus 2 way radios, I think that could be your problem...

Are you using the external power supply that came with the OI? Or by any chance have you swapped it out, and are now using a <1200mA power supply?

In a prior year, we lost one of our power supplies and replaced it with one that we picked up somewhere along the line. We didn't bother to check to see if it had the same rating as the ones that come in the kit (1500mA). The replacement was just a 1 Amp supply, and when we plugged it in and turned everything on we experienced the same symptoms you are seeing. The OI powered up, seemed to run perfectly, but the signal to the RC kept dropping out.

Replacing the replacement power supply with one that really provided 1.5 Amps solved the problem. I forget the exact part number, but you can pick them up for about $21 from Radio Shack. If you do a search on the forum, the answer is in another thread somewhere (this problem was discussed earlier in the summer).

-dave

We had similar problems when the battery chargers were plugged in on the same circuit as the transformer for the operator interface.

We had a similiar problem the night before shipping this year. Four hours including one on the phone with Innovation First did not resolve it. I could not repeat the problem when I took the OI and RC system home.

Thinking back, we did have the chargers and the OI power supply on the same power circuit.

It is usually the simple things that get you.

From this, I'd guess any electrically noisy equipment might be causing your problem. Any motors, vacuum cleaners, hairdryers, battery chargers, heat-shrink guns, old light fixtures, etc plugged in with the OI?

i hate this problem...

we had it for a while, and we couldn't figure it out. we tried swapping RC Radios, serial cables, everything (or so we thought). then, one day last week, i picked up the OI Radio, and pushed the cable in as far as it would go (i thought it was in all the way already, but i'm like that), and our problems disappeared. it turns out that our radio connector is loose, or it's picky, and needs to be placed exactly right. not a huge problem now for us, but still a pain.

Haha, yeah we had that happen to us at a demo once!

It was our 2001 'bot that we were demoing and the arm just would not move. It took us almost the entire demo to solve, because we were testing everything electrical that we could think of!!

Turns out it was the radio not being plugged in all the way :rolleyes: Grrr. I hate that.

- Katie

lol we actually had the problem during a demo, and didn't fix it till later. that demo sucked...a lot. nataku can testify to the suckiness of that demo :).

Think about all the good experience you're getting finding glitchy little problems. This will stand you in good stead come competition time.

One of the things that hasn't been mentioned (though I'm sure this is not your problem) is to make sure you're not running two OIs and RCs at once.

In our second year, we were testing the new OI/RC in one room and driving the previous year's robot in a nearby room. The robot kept acting as if it were being controlled by some "higher power." Turned out, it was getting commands from both OIs. It was also experiencing cut out problems, etc.

We also had problems this year with Robot Reset Cut Out problems. We're now pretty sure that, because our robot drew buckets of current to operate the various devices, the battery was getting pulled down below the RC operational threshhold or the modem was not putting out enough signal for the OI to continue "hand-shaking." We only use fresh robot batteries now. On another thread, it was posted that the 2002 batteries couldn't pump out as much juice as earlier year batteries. Perhaps that's part of the problem.

It's really hard to figure out these problems when they only occur in competition. Now that we are really beating on our robots in demo season, we're starting to pick up more clues as to some of the weird behavior we saw during competition.

The other spooky problem that we experienced at 2002 Nationals turned out to be our tether cord (although this same problem could occur with the radio modem cord). Someone probably stepped on the cord and broke one of the connections. During competition, all was well. In the pits on tehter, the commands from the OI seemed to be randomly turning on some of our devices. We thought it was a programming error and spent countless frantic hours trying to debug it. One of our engineering students got the bright idea to scope the cable. Viola! No continuity on one of the pins. The cable made it into the trash can in record time.

Andrew, Team 356

Yes, that happens because without the competition port adapter, the OI's are defaulted to channel 40 and the other channel's are not avalible, to fix that you can either run one on a tether, or make an adapter for the competetion port, info on that is found on IF's site :
http://www.innovationfirst.com/FIRST...Operator_..._Guide.pdf

This problem pops up occasionally and everyone has pointed to their experience.
The cable between the interface (Robot side or operator side) and the modem can go bad after months of banging around especially if kinked. The modems operate at just above 900 MHz, in a band licensed for public use. (i.e. walkie talkies, home wireless phones, remote data links, security cameras.) Rough handling has occasionally caused some internal damage on either radio modems typically the antenna. If the cutout is occuring at regular intervals, check for things like a new weather radar installation nearby, aquarium heaters or wireless lighting controls in a nearby conference room or classroom. As a last ditch attempt, see if you can borrow a spectrum analyzer to monitor the band and see if there is anything present at the frequency of the radios. It will tell you if there is an interferring signal or if your radios are not generating signal.
Good Luck

It seems that many people are having trouble with the modems. Just be glad that we still aren't using the RNets (pre-2000) ;-)

We know it isn't rough handling, as Al suggested because it happens with all thier robots, including the EDUbot. I would think it is some type of interference, as other people suggested. The only way to find out for sure is to get a spectum analyzer as Al suggested.

2.4 Ghz
 

Perhaps it's time to move to 2.4Ghz, maybe even run the robots over WiFi or 802.11b. Instead of serial cables, use network cables.

Now thats the future... lets put all our robots on wi-fi. So anyone with a wireless card/laptop could mess with the robots. ( I'm sure someone could manage to do that with a Linux Laptop with Wireless card ) Of course only if it's standard wi-fi and using tcp/ip to talk to the robotics... Which I'm sure could be done with Java ran robots...

You think you have connection problems? Try testing you're bot in an Army research building. I have no clue what they were playing with, but it will probably give me cancer some day. Even worse, caused all kinds of trouble for the 'bot.

Thank god we got out of there!

-Andy A.