howdy everyone, I have been thinking about all the talk about people hacking apart remotes, putting infrared LEDs in series and the like. Our team has a simple remote control for our transmitter and is using the FIRST supplied ir receiver. I was wondering that if I were to hack a few more infrared LEDs into the remote, what wavelength LED would I need to use?
I know it would have to be considered infrared but within, but does the ir receiver only recognize certain wavelengths of infrared emission? Does it really matter? Ive been looking at a bunch of LEDs with 940nm and some with 850nm wave lengths. Any help would be greatly appreciated.
Remember to look at both the sending element and the receiving element characteristics. The receiving element on the KOP board is the Vishay TSOP34838. I found the Vishay datasheet and Figure 11. Relative Spectral Sensitivity vs. Wavelength shows sensitivity from the range of 750 to 1150 nm.
It is greater than 50% from 825 to 1075 nm and peaks around 950 nm. Therefore, your selection of sending element frequency will tend to have minimum impact on the system design because the receiving element has a wide range of sensitivity. I will attempt to attach some pdf’s for your reference.
Vishay_TSOP348.pdf (149 KB)
Vishay_IR_Guide.pdf (1.31 MB)
FIRST_IR_schematic.pdf (25.3 KB)
Vishay_TSOP348.pdf (149 KB)
Vishay_IR_Guide.pdf (1.31 MB)
FIRST_IR_schematic.pdf (25.3 KB)
I suspect more can be gained by moving the carrier frequency away from the usual 38KHz to 56KHz. This would, of course, mean that you’d have to find a remote that used a 56KHz carrier, or invent your own. If you’re really hard-core, you’d invent your own data protocol with a error detection (and possibly error correcting) wrapper to ensure you’re getting good data. You might get some ideas by studying my 2004 beacon code and transmitter circuit. A perfect transmitter waveform generator would be a EDU or Vex robot controller. Of course, if enough folks are interested, I’d be willing to help out.
-Kevin
Good idea!
We have actually switched our setup over to a 56KHz system. This year, we were lucky enough to have the help of two alumni who just got their degrees (Computer Science and Electrical Engineering), and without them we’d never have pulled it off. As I understand it, they switched the IR receiver on the IR board to a different model, and built a custom remote. I had nothing to do with it, so I don’t know the details, but apparently it wasn’t particularly hard. We never got it mounted before ship, but we should be able to see if such a change is actually useful next week.
I switched over all the IR boards for the Chief Delphi team to use the 56 kHz Vishay TSOP IR part. This is just a matter of desoldering and removing the existing 3 pin piece and replacing it with the Vishay TSOP 34856. The units still work with the limited number of IR remotes tested (2) and still have jamming when both units are pressed at the same time. 
There is also a Vishay TSOP 7000 IR component that works at 455 kHz. My searching revealed that this is an uncommon remote frequency and I couldn’t locate an inexpensive remote
that works at that frequency. I will post the Vishay TSOP 7000 IR pdf for reference.
Vishay_TSOP7000.pdf (129 KB)
Vishay_TSOP7000.pdf (129 KB)