If you want to connect a GP2D12 Sharp IR sensor to an NXT cable, you'll need something to increase the signal, otherwise you will continually get the value "900" or something around there. (Where you should actually be receiving a value 0-1023 scaling to this distance).

You can solve this problem with a transistor or resistor. I got this working using a "2N 3906 PNP General Purpose Amplifier".

To wire this connect as follows.


Sharp sensor yellow wire <---> Middle transistor pin (Base)
NXT white wire <---> Left transistor pin with the flat side facing you (Emitter)
Sharp sensor black wire <---> Right transistor pin with the flat side facing you (Collector)
NXT green wire <---> Sharp sensor red wire
NXT black wire <---> Right transistor pin with the flat side facing you (Collector)

Don't use the other NXT wires.

With these 5 solder points, your GP2D12 should now give you values between 0-1023. Happy Soldering!

Thanks for that! If you have some pictures, that would be great

- Xander