Interesting IR sensor test results

[Mr. Freeman]

Originally Posted by SpartenSoldier

When the remotes were jamming each other did the frequencies of the remote matter or did any frequency jam any other frequency?

I didn't change the frequencies on the 5 remotes I picked up. One was for something made by JVC, one was for a receiver/tuner, one was for a different tuner, one for a DVD player, and I forgot what the other one was.
So I guess any frequency will jam any other frequency.

[Bongle]

Originally Posted by Mr. Freeman

I didn't change the frequencies on the 5 remotes I picked up. One was for something made by JVC, one was for a receiver/tuner, one was for a different tuner, one for a DVD player, and I forgot what the other one was.
So I guess any frequency will jam any other frequency.

This would make sense. IIRC from 2004 when we had those IR receivers in the KoP, it only outputted a 1 when there was IR, and a 0 when there wasn't. So it would see no distinction between different frequencies, and therefore the IR board wouldn't be able to either.

Are you sure that flesh is transparent to IR light? I'd think a more probable explanation is that it reflected off your hand to surrounding walls, and then got picked up by the sensor. You could test this with an IR night-vision video camera and see if the room gets lit up when you fire the tv remote.

[mneary]

Most IR remotes use one of three frequencies; 36, 38, and 40 KHz. But their light outputs are all the same IR; the sensor will see them all.

IR remotes and their receivers use different codes, not different frequencies. If you're sending one code while someone else is sending another, the chances of either one getting through without errors is very small.

Try this at home: Hold the button on one remote (VCR?) and then try to use another (TV?). Very seldom will it work. There will be up to six robocoaches operating signaling devices during the Hybrid period.

[abeD]

I know for one of my college classes we had to make an IR receiver transmitter for a robot we were using and we could control the frequency at which we broadcasted the signal and would just make a good enough filter so that the phototransistors would only see close to this frequency. If you are allowed to do something like this you would get no interference from anyone else (as long as there not on the same frequency but you can ask them and can change your's accordingly if your setup allows it)

I haven't read the specifics of what your allowed to use but this consists of a simple IR LED's and some phototransistors which I don't think are against the rules.

I am also not on a team anymore so I haven't seen the receiver board or any spec sheets for it.

[JHSmentor]

Originally Posted by abeD

I know for one of my college classes we had to make an IR receiver transmitter for a robot we were using and we could control the frequency at which we broadcasted the signal and would just make a good enough filter so that the phototransistors would only see close to this frequency. If you are allowed to do something like this you would get no interference from anyone else (as long as there not on the same frequency but you can ask them and can change your's accordingly if your setup allows it)

I haven't read the specifics of what your allowed to use but this consists of a simple IR LED's and some phototransistors which I don't think are against the rules.

I am also not on a team anymore so I haven't seen the receiver board or any spec sheets for it.

Do you think this would something you could/would build around the exisiting IR board and receiver that where given to us? kind of like a filtering shield that only lets in the frequency that you will be transmitting?

[k4r3n2]

Did you press the same button on the remote that you were jamming it with (i.e. play and play)? We haven't started playing with our IR board, but I was curious as to whether the selection of the buttons would affect the effectiveness of the board, i.e. if we picked obscure buttons, our signal would work better. Thanks for posting your testing results! I find it very interesting that it works for 360 degrees, most receivers apparently aren't good for over a 100 degree span.

[abeD]

Originally Posted by JHSmentor

Do you think this would something you could/would build around the exisiting IR board and receiver that where given to us? kind of like a filtering shield that only lets in the frequency that you will be transmitting?

Yea that's what I was trying to say although i have no idea if that is possible with the given board. Someone else that's actually working with this thing will have to say.

[Lions for First]

i dont know all that much about IR but what kind of "filter" would you use that blocks all other frequencies but one?

[abeD]

You don't block all frequencies but one (if you could do that simply then you would be making alot of money) but with some combination of low pass and high pass filters you can get a nice bandpass of filters centered around where you are transmitting. Do a wikipedia search on filters and try to get through it. All of the stuff I've learned about is college level engineering so it might not be the easiest thing to understand.

There are also several types of active filters as well that have a sharper "edge" to them on their bode plot. (a magnitude vs. frequency plot).

[JHSmentor]

Originally Posted by abeD

You don't block all frequencies but one (if you could do that simply then you would be making alot of money) but with some combination of low pass and high pass filters you can get a nice bandpass of filters centered around where you are transmitting. Do a wikipedia search on filters and try to get through it. All of the stuff I've learned about is college level engineering so it might not be the easiest thing to understand.

There are also several types of active filters as well that have a sharper "edge" to them on their bode plot. (a magnitude vs. frequency plot).

I like the idea of it but don't know how either. I read some patents and some college papers and it's a bit confusing (particularly because I could not view any of the images).