Optical Detector / Phototransistor

kenwtn

Hi All,

···· I was given a couple of Optical Detector / Phototransistors and I understand they can be used to detect changes between a white and black surface. What I was hoping was to use 1 to detect wheel movement on my robot, but I can not find any examples of using them. There is 2 leads to the E and 2 lead to S. Does anyone have a example of connecting them to a BS2 and code to read them?

Mike Green

The Parallax Wheel Encoder is pretty much what you have, more nicely put together. Have a look at the documentation and sample code that comes with it. Parallax's device uses a modulated IR emitter and tuned detector, but the same principle applies. Your LED needs a series resistor that provides for a 15-20mA current. With a +5V supply, a 220 Ohm resistor should do (cathode to ground, anode to the 220 Ohm resistor). The phototransistor should have its emitter grounded (to Vss) and the collector should be connected through a 10K resistor to +5V and through another 220 Ohm resistor to a Stamp I/O pin.

www.parallax.com/Store/Microcontrollers/BASICStampModules/tabid/134/List/1/ProductID/80/Default.aspx?txtSearch=wheel+encoder&SortField=ProductName%2cProductName

Post Edited (Mike Green) : 6/18/2008 3:19:55 PM GMT

kenwtn

Thanks for the quick reply