IR Sensors- will they attack hot Chiaphuas?

[Wayne C.]

Scenario- it has been a long hard day and your Chiaphuas are too hot to touch- its the elimination rounds

what will an IR sensor home in on? A light bulb 20 feet away or your neighbors drive system 5 feet away.

Now that might be a real Frenzy- when robots attack!!

Just a thought......he he


WC

[Pierson]

I had a similar question: What about all of the other IR interference that comes from the cameras and camcorders in the stands. What about the Media who bring cameras and video cameras into the area right around the outside of the field? What about the cameras that feed the big screen?

For those of you who don't know, the auto-focus on your camera relies on an IR signal being bounced from the camera to the object and back. This tells the camera the focal point.

Will we see robots attempting to leave the field to attack the media? Or, has FIRST put the IR on a different frequency or spectrum (I don't know if this is possible)?

[Pteryxx]

Originally Posted by Peciv

....
Will we see robots attempting to leave the field to attack the media? Or, has FIRST put the IR on a different frequency or spectrum (I don't know if this is possible)?

From TheArena, 3.2.5: "Each beacon emits at the same IR frequency, but sends pulse trains of different widths.... FIRST has supplied appropriate code that allows teams to program their robot's controller to make decisions based on a received signal and discriminate between the two Tee locations."

The beacons are not just a flashlight IR source, they send a modulated signal on a particular frequency. Robots using the code should be able to ignore most IR interference - though IMHO, testing with interference would be a good idea. I notice the humans were careful to stand far far away from the demonstration 'bot ; ) -Piece, Pteryx

[Mike AA]

These IR sensors detect light not heat so there isn't a possibility about them being attracted to another robot or something hot

[Wayne C.]

Originally Posted by Mike AA

These IR sensors detect light not heat so there isn't a possibility about them being attracted to another robot or something hot

IR is a form of light beyond the range of human vision but it is a form of radiant heat. My question is- does a heat source emit a specific wavelength or a broader spectrum of wavelengths including the ones sensed by the sensors?

Second scenario- the processors of the sideline computer control station emit a heat source or maybe have IR networking.

It would be fun to see all the IR sensors in the arena make a beeline for the control team. A real frenzy- who can hit who first- the robots take out the controls or the operators hit the stop buttons.

I'm sitting way up in the stands this season...
WC

[Mike AA]

Originally Posted by Wayne C.

IR is a form of light beyond the range of human visionbut it is a form or radiant heat. My question is- does a heat source emit a specific wavelength or a broader spectrum of wavelengths including the one sensed by the sensors?

Second scenario- the processors of the sideline computer control station emit a heat source or maybe have IR networking.

It would be fun to see all the IR sensors in the arena make a beeline for the control team. A real frenzy- who can hit who first- the robots take out the controls or the operators hit the stop buttons.

I'm sitting way up in the stands this season...
WC

Ok, you should experiment with infrared sensors and a detection card to see what it does. These infrared emmitters and detectors OPERATE AT A SPECIFIC FREQUENCY. Thus the emmiter (on the sideline above the balls in the center) does bursts of light, on and off repetidly at a certain speed. simmilar to your TV remote. you cant take any remote and make it work with your TV it MUST be on the correct frequency.

Just believe me, the robots WILL NOT go for heat.

by the way. it would NOT be fun for a robot to take off after a control table. note the words CONTROL TABLE. if this happened it would take time to fix everything.

[Rich Kressly]

Originally Posted by Wayne C.

I'm sitting way up in the stands this season...
WC

Don't you every year Wayne?
Get some sleep, you are getting goofy already
Have that 9 ft arm built yet?

[Anthony Kesich]

40khz is the wavelength at which the beacons will be transmitting (I'll find the quote in the manual later). If I ma not completely mistaken, that is on the high end of the infared spectrum, just below the visible spectrum, so for someting to emit infared light from being hot, it would need to be REALLY hot, and i think most CIMs will die before getting that hot.

[briholton]

Originally Posted by Anthony Kesich

40khz is the wavelength at which the beacons will be transmitting (I'll find the quote in the manual later). If I ma not completely mistaken, that is on the high end of the infared spectrum, just below the visible spectrum, so for someting to emit infared light from being hot, it would need to be REALLY hot, and i think most CIMs will die before getting that hot.

yikes! 40 khz is not a wavelength - it's a frequency - and I don't think it is the frequency of the electromagnetic radiation coming from the source either. If that were the frequency, the wavelength would be about 10,000 meters. That's a real long radio wave, not infrared. So, yes, you ARE completely mistaken. Perhaps the infrared source is being pulsed at 40khz, but that's a whole difference animal.

[Gary Bonner]

How many pulses must the sensor receive in order confirm which beacon it is seeing, and therefore, how fast can the sensors sweep the field and still detect the beacons?

And a less important issue, will the beacons appear as bright lights on videos of the matches since many camcorders are sensitive to IR light?

[Rickertsen2]

Originally Posted by Gary Bonner

How many pulses must the sensor receive in order confirm which beacon it is seeing, and therefore, how fast can the sensors sweep the field and still detect the beacons?

You don't really have to worry about how many pulses they need to see. at 40khz, this will not even be an issue. You can basically assume the response is instantaneous.

Originally Posted by Gary Bonner

And a less important issue, will the beacons appear as bright lights on videos of the matches since many camcorders are sensitive to IR light?

yes. Some cameras more than others. It will show up as bluish white. Point a TV remote into your camera to get an idea of what i mean. You can prolly find IR filters if things are really bad.

[ahecht]

Just to make it clear, these sensors use near-IR, which means the light they use has a wavelength somewhere between 0.75 and 1.25 microns. Thermal IR, on the other hand, has wavelengths of between 3 and 30 microns. Heat will not be a problem.

Also, interference will probably not be a problem. The beacons (like most IR devices) emit bursts of light of varying length, which they use to send a coded message, similar to the way morse code can be used to send a text message (I am not certain what coding scheme is being used, but there are many commonly used including NEC, Sony, Toshiba Mincom, RC2000, RC5, RC6, IrDA, etc.). The Robot Controller can be programmed to look for this message, and if it isn't what it is expecting, ignore the signal.

Furthermore, each burst is not actually a solid burst of light, but is chopped up so that when the beacon is bursting, it is actually flashing 40,000 times a second. Inside each detector, a circuit called a bandpass filter removes all signals coming from light that isn't flashing near 40,000 times a second. Since most IR devices don't operate at 40kHz, most signals will never even make it to the Robot Controller.

[ErikJ]

Al pretty much nails it. The whole modulation thing can be tricky for anyone who hasn't seen it before, so that's probably the big cause of confusion (ie, IR frequency != 40KHz).

However, it should be noted that nearly all (I think it's all) TV/Stereo remotes operate at 40KHz (it's actually just a shade off). Most off the shelf commercial IR sensors (ie, the kind you buy at Radio Shak) only look for this 40KHz signal, and filter everything else out. The way your TV, and your FIRST robot, know the difference between the signals is in the coding scheme used on top of that 40KHz carrier. So... if you go off and write your own code, yes, TV remotes could be a source of interference. Or, perhaps cooler, you could probably allow (for demo/debug purposes) the FIRST controller to use a TV remote as an input, provided you knew the coding scheme of the controller (you can find many of these online).

Something I haven't seen made mention of yet is multipath interference*. I worked on an IR project a few years ago and would get strong multipath interefence when I was transmitting near large metal objects (in this case, lockers at the HS we were working with at the time). I'm interested to see if this becomes an issue, especially as one or more robots approaches the beacon. I'm not sure if this will be a major issue (I suspect not, but it could be depending on robot geometry), but the fix should be simple enough if it is.

* multipath interference - in short, when you recieve a signal that has been reflected off a few objects before you receive it. for example, in a car radio you have a direct path (radio tower to you), and a ground bounce path (tower, ground, you) - mutliple paths, hence multipath interference. In our example, this means that robot reflecting IR waves from the beacon appears to be a source, potentially causing problems for your location algorithm.

[Wayne C.]

Originally Posted by Rich Kressly

Don't you every year Wayne?
Get some sleep, you are getting goofy already
Have that 9 ft arm built yet?

20 ft.....

[Curtis Williams]

What I meant about last year's sensors is that they sent a specific pulse pattern to prevent picking up sources other than itself. Although my team didn't use them, I played with the sensors and found them pretty reliable. I dont think we have to worry about someone accidentally confusing the robots with a camera or furby.