I have a pretty good supply of electronics I keep in stock… I have an array of microcontrollers, an FPGA dev board, all of the transistors, resistors, diodes you can shake a stick at. Common ICs that you’d use for the normal run-of-the-mill circuits. Hell, even non-run-of-the-mill stuff too like a collection of high bandwidth transimpedance amplifiers (TIA).

But I go down to the shop to find either a photodiode or a phototransistor and I come up empty. :-(

Why am I looking for a relatively fast photodetector? To reverse engineer a really cool headlamp from Petzl: the Reactik+. It adjusts to what you’re looking at almost like magic. But I think I’ve determined the magic completely: it runs kind of like an over-simplified lock-in amplifier. But I need to be able to examine the light in high speed to get a handle on it.

Alas…

At least the TIA will come in handy for the photodiode. Wire that puppy up and probe it with the scope… good times.

Now to think what other stuff I need in the storeroom when I put together an order tonight.