How do I use a 3 legged phototransistor? I have searched the Internet and found the following circuit to use with my phototransistor but it is not working, I can say so because all analog input i get is 1023 even if i have covered it totally, I have include the phototransistor and the diagram can anyone tell why is it not working!
I used this webpage to check my sensor and it works-I used this page

I have used 10kohm resistor.



This is my phototransistor
A reasonably generic data sheet is HERE
That is for an AT156 but yours may be an AT138/HT138 based on an ad some years ago from the same seller when they said they had 10,000 for sale.

Basic information here and more in the data sheet.