HP 50G - Any way to increase the IR TX/RX range?

[Dave Shaffer]

As Martin Hepperle commented, it should be practically trivial to build a pass-through transceiver. I have some IR-sensitive phototransistors that should work as a detector, which would operate a transistor switch that turns on/off an IR emitting LED of almost whatever power level you want. A quick check on Ebay shows 3 watt and 10 watt (!) IR LEDs. The switch on/off times of these are at the few microsecond level. Parts cost would be a buck or two, not counting battery and packaging.

Does anybody know what the wavelength of the HP50 led is? And what is the signalling rate? If it is 100 kilobits per second or more, fast detectors and emitters will be needed!

I don't have a '50 or any other HP LED-equipped calculator, but I will try to play with one of my TV or CD player remotes to see if I can make a simple transceiver. I don't have any of those high-power LEDs either, but I should be able to make a red LED blink to show that I am receiving signals.