Let's Make Robots!

ok i think i have a phototransitor... over 500 of them or diode

right i have recently found out that i have about 500 photodiodes or phototransistors. 
however i have never used these before and i dont really know what they do or how they work, could someone please explain what i can do with them and what use they are to me.






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.. to be brief. It's just like an NPN transistor but instead of providing current to the base to turn it on it uses light. It has a pretty wide range of detection but it looks to be more specifically for IR and near-IR wavelengths.

A very quick search for phototransistor circuit turned up a simple schematic and a decent explanation.

ok turns out they are photodiodes ....what could i use these for ? 
any ideas
sensors or anything 

mentions both phototransistors and photodiodes. If they are indeed photodiodes they will likely require an amplifier to be more readily used.

500 may be a bit of a stockpile for an individual, but, if you were part of a group, you could share.

Your linked datasheet at least, calls them a phototransistor.

Either way, that's a lot of them.

They are good for general light sensors to determine ambient lighting conditions. You can make a robot that responds to changes in light conditions.

Two phototransistors/diodes at the front of your robots pointing slightly outward in opposite directions can make a nice light follower.

You can pair one or more with a light emitting source to create a obstacle sensor. In this case you may need to match the sensitivity range (should be found in the datasheet) with the wavelength of of your emitting LED or other light source. It may help to shield the photodiode/transistor from other light sources.