IR Sensors- will they attack hot Chiaphuas?

[Anthony Kesich]

ahh, good point. I'm used to constant signals, but who knows? I think some experimenting is in order. Maybe some interrupts to collect the strength for 2 ms... hrmmmm

-Kesich

[Curtis Williams]

Wouldn't these things be as realiable as the sensors from last year we used to detect the reflective tape? I think they worked the same way.

[Anthony Kesich]

Didnt those use the visible light spectrum? And the light sensors projected, whereas the IR sensors just pickup, so there really isnt the chance of seeing reflection when there isn't one. I went straight dead reckoning, though. Getting to the top of the ramp and hitting boxes in 5 flat seemed better to me. Anyways, in the line vs IR arguement, i'd say IR because you can see the IR from anywhere. The line, on the other hand, can get smugged up, lost, and once you are done with it, the sensors are useless. Ir can triangulate though.... hehehe

-Kesich

[Adam Y.]

The signal from the beacons and receivers probably resemble the signals from a television remote. I have never encountered any interfernce from body heat on those things.

[Anthony Kesich]

Wouldn't that be funny. Walk by the TV with a candle and the tv turns on, mutes, unmutes, cranks the volume, then hacks the cable box and gets you free PPV for life. Heheheh :-D

-Kesich

[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.

[Witte1]

Originally Posted by Peciv

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)?

The IR Sensor is set to only detect the frequency emitted from the beacon. Similar to way your TV remote works, you won't get out side interference.

[Al Skierkiewicz]

OK,
Before you guys get too crazy, the IR emitters generate energy in the same area as heat but have one distinct difference. The emission will occur as 40kHz pulses for varying lengths of time. That is, bursts of 40kHz modulated IR energy. The night illuminators on cameras are just that, steady state, non modulated sources the same as hot bodies. The IR camera range finders and remote controls use modulated IR emitters at different frequencies so there should be no real problems if you keep in mind that you are looking for a 40kHz modulated source. The bandwidth of the IR is not 40kHz but likely is much wider than that since the bandwidth you are measuring is near visible light.

[Kevin Watson]

Originally Posted by Al Skierkiewicz

OK, Before you guys get too crazy...

Too late .

Originally Posted by Al Skierkiewicz

That is, bursts of 40kHz modulated IR energy. The night illuminators on cameras are just that, steady state, non modulated sources the same as hot bodies.

Yes, as Al correctly (again) points out, the Vishay TSOP4840 sensors that are included in the kit and also used for the kick-off demo specifically discriminate against these type of energy sources. They also discriminate against non-modulated 40KHz sources. I've put a link to the data sheet here: http://kevin.org/frc. The modulation scheme is discussed in this thread.

-Kevin

[Joe Beynon]

this is something that i asked about at the main kickoff because of the fll problem. the guy told me that he tested the ir sensors with 5 cameras that were said to have problems with the fll bots and none of them caused interference. he also mentioned that these ir sensors are the type used in high-end stereo equipment and the only thing to possibly worry about would be a flickering flourescent bulb.

[Al Skierkiewicz]

Kevin,
Thanks for the pdf, I am forwarding it to our electrical guys right now. Good info in the data sheet, too!

[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.