Wednesday's circuit ...

We'll add a little amplifier to our photodiode to boost the signal. If everything works out, we should be able to pick out the blinking LED from a meter away or better without any additional cleverness. Increased cleverness can boost the range to several meters, which we'll worry about next week.

Here's the circuit. Basically, the voltage applied to the photodiode will lead to a current when light is incident. This current is converted into a voltage and amplified by the little triangle in the diagram :-) Explanations will be in order ... and it might take more than one class period to get it going (both on the board and in your head), but it will make sense shortly.


Other details: the voltage "Vcc" will need to be about 12V, so you will need an additional power supply.

(If you have taken a real circuits class, you'll see some problems with this thing ... but it does work, and we want to start reasonably simple!)