I just looked at the 2014 FRC Inspection List and under Robot Radio it says, “Radio must be mounted so that its LEDs are visible to field personnel” and referencing R62 The Wireless Bridge must be mounted on the ROBOT such that the diagnostic lights are visible to ARENA personnel.
Well, our electronics board is installed with drawer sliders and is located under the robot deck. My thinking is that the “radio” router is not going to be allowed underneath there. We were only worried about inspection where we could roll the board out on the drawer slides.
I think if you are at the right angle, you might be able to see the lights, but without being next to the robot until tomorrow, I won’t know.
So I guess we’ll have to mount it up on the deck somewhere or am I misunderstanding it?
Thanks for any input. If I don’t respond it’s because the internet at the school won’t allow me to post here, but I can read everything. Weird but that’s the way it is.
Couple of things. For the Arena personnel being able to see your router makes it easier to diagnose why your robot won’t connect to the field. Also, we in the past have made the mistake of mounting our router low down in our robot…Invariably this made it so that our robot would not connect to the field, or would connect, only to lose connection mid match. The robot itself provides interference making it difficult to maintain a connection, especially in a noisy environment. As a result we decided to always mount the radio higher up on the robot and out in the open if at all possible.
Visibility of the router can only be for your benefit - the field personnel use it to help diagnose issues with your robot and team.
Additionally, it’s a good idea to mount your router high up, away from metal and away from RF-generating sources (like the motors). Having a router buried inside a robot makes it much more likely that you’ll lose connection during a match!
Is there any reason why you wouldn’t be able to mount the router close to any other electronics, such as Crio and Digital Sidecar? Just double checking because we normally do this, and we have a track record of having more connection problems than other teams…
Keep the router away from electrically noisy components. That includes the Power Distribution Board, the cRIO, the Digital Sidecar, the 12v-to-5v converter, motor speed controllers, and ethernet-to-can gateways.
If you regularly mount the D-Link near other electronics, and you regularly have connection issues, take it as an indication that you should stop doing it.
I wondered earlier if there could be a problem with the router and the network cable near motor controllers. I know if it was a big A/C freq drive like I work with, it could be a problem, but didn’t really consider it much with these small DC drives.
Well, being that our router will now have to come out of the basement it will be away from most things. I’ll have to tell them to not put it near a motor.
I also hadn’t thought about connection issues. That’s a good point.
From having spent many hours in an EMC test lab, I definitely recommend you take Alan’s advice. I sometimes view the AC motor drives I do R&D on (88-2000 hp) as noise generators that are their own worst enemy.
I made my feelings known today, and to no avail, so if there is a problem, I’ll stand back and say, “Told ya so” and go from there.
The lead mentor believes that as long as the field person can come out to the robot and see the router lights without too much trouble, we’ll be OK. I’m going to have the kids mount the router at an angle so that it can be seen looking down into the front, just above the bumpers. If inspection says something about that, then again I can say, “Told ya so.”
I am fighting the shop right now because they wanted the electonics on a drawer, and both times it was test fit, it didn’t. The first time they forgot to take into account the height of the cRIO. This time new items they mounted on it blocked the drawer from even starting to slide in, so they rotated the drawer 180° and although it still didn’t fit, they want that. So now all the electronics have to be removed and installed differently, and where I was told we could run wires from side to side, is now not available for wires. All this and they expected a running robot today. Very frustrating for me being a rookie mentor.
I just told the kid in my electronics team that I will be there when they try and blame us for any problem or being late, and I will remember that the shop changed everything for us twice (so far). The mentor in charge of the build (also a rookie) complains about a lack of communication between teams. I guess he feels that being in charge of the build means he doesn’t have to communicate with anyone.
After 27 years of being in a union shop, I’m used to getting blamed, so its no big deal to me at all. I’m just going to go to bat for my students because they’ve done everything they’ve been asked to do.
Sorry to hear about your trouble with “office politics”. Your students are getting an early look at what they are likely to have to face in the future. Hopefully, your students will understand why you are telling them to do certain things like “communicate frequently and clearly with the other departments”.
If it were me, I’d be sure to print up a few cards that say “I told you so!”, so when it happens at inspection (and it will), you can hand them out.
To help your kids manage the stress when they fail inspection, have them think of exactly how they are going to fix it, and make up all (or many of) the wires, brackets, and things they’ll need to do it in the pits.
Try to have it visible. It makes it easy to debug what is going on. Also, make sure you can tether to the bot easily. It’s very annoying to lift the robot and worry about the wire getting stuck in the wheels to just tether to it!
Also, KEEP IT AWAY FROM THE CONVERTER!!!
That tiny box is actually a tiny box with a big potential of interference!
Please let the lead mentor know that many people with years of experience as FRC technical advisors say to put the wireless bridge out in the open. Not just because it keeps the lights visible, but because it is a radio transceiver. If it’s surrounded by enough metal and electrical components to make it hard for a person to see, it’ll very likely be hard for the field’s wireless access point to “see” it too.
I said to him, “So we to are ignore those that posted that they’ve had problems?” His response was that it’s hardly metal 'cause it’s aluminum. I believe he has expertise in networking, but I honestly don’t know how much.
I’ve had an offer for me to take a pic tonight and it be shown to a chief inspector and at least I’ll know if its ok to be almost hidden.
I’m also having the kids leave enough power wire, held by a tie wrap, so that it can quickly be mounted on the deck. I asked for a hole thru the wooden deck in case, but I know that will be ignore.
I don’t push my knowledge and electronic degree on the other mentors if they decide that things are to be done a certain way. I figure they should know more about building the robot and the rules than me. I think new blood is not always appreciated.
I know the following is likely to be lost in the bowels of CD:
While we are on this subject, try to mount your Radio “Pancake Style” to maximize the use of the two antenna’s in the router with the field access point. Ideally mount it about at least 18" off of the ground.
You will maintain a higher quality connection if you do this. You do not have to do this, it is a best practice.
As for making the router easy to find, my colleagues around the field will thank you. We will further thank you if you make it easy to observe the status lights on the CRIO, although we do realize you can just follow the ethernet cable out of the back of the router. Making our life easier is like giving us cookies.
Drawer Slides: Did your team realize that if you use drawer slides, you can’t use the “slide” feature after it is all wired? I learned that my rookie year the hard way. Back in the IFI days when we used drill motors as the kit drive.
When trying to impart the wisdom of others, one thing to point to is the signature of guys like Don and I. I am a broadcast engineer and Extra Class Ham Radio operator. Don is a Ham with significant digital experience. Alan is a trusted network and software specialist with a lot of wireless experience.
Aluminum at 5 GHz might as well be lead.
For everyone, the DAP-1522 has two antennas mounted on the board. They are verticaly polarized with respect to the bottom of the AP/Router. That means they are most sensitive to radiation out to the sides, front and back of the radio. The circuit board is a ground plane effectively blocking all reception in that direction (out the bottom of the radio). The nature of 802.11N is that both antennas are required for max bandwidth to be achieved. Both are used for receive and transmit. In addition to the shielding effect provided by metallic objects, the metal serves to de-tune the antennas making them less effective. This effect, of course, is distance dependent. As Alan has pointed out, there is some significant noise generators on the robot. Of those that are the worst for interference is open frame motors (those that you can actually see sparks through the openings in the sides of the motors), the five volt convertor power supply, and the supplies in both the PD and the DSC. These noise sources not only interfere with radio reception, they also impart noise directly to the electronics on the board.
Having the radio mounted in the robot such that is “visible” to the antennas on the field, it is not mounted near a noise source and it is not surrounded by metal of any kind is the best of all worlds.
One word on “visibility”, inspectors want to be able to help you and insure that you will play all matches at every event. If your mounting is questionable it may pass, but if you want help when you fail on the field, you have to meet us halfway. If we can’t see the lights from several feet away when you are dead in the middle of the field, we have to rely on the field logs only, to try and figure out what went wrong. After repeated connection issues or a string of bad packet events we will ask you to move the radio to help you improve.
Thanks Al! This is extremely informative. I learned my lesson when we have had radio problems in the past, and ended up fixing the issues by simply moving it. I try to stress this to my current students, I will definitely pass this on to them! It’s a good explanation. … and since your a HAM, I’ll say 73 AL! Thanks!
Thanks to Don, Al and Alan for your wisdom here. In your experience, does the signal light impart any interference with the radio signals? We are currently planning to mount them near each other so that the field crew can find them easier.