Saturday, June 2, 2012

Reflective Optical Sensor with Transistor Output

Hacktronics sent us another goody package, containing a very cool LCD Shield, a couple protoshields, and these IR emitter/detector pairs. The TCRT5000 is a reflective sensor which includes an infrared emitter and phototransistor in a leaded package which blocks visible light. The "blue" LED is the IR emitter.

These units have been used for:

• Position sensor for shaft encoder
• Detection of reflective material such as paper, IBM cards,
magnetic tapes etc.
• Limit switch for mechanical motions in VCR
• General purpose - wherever the space is limited

Our goal is to make a tachometer for tools and testing rigs. One of our projects is a motor test jig. We are measuring volts and amps using our previous amp hour meter project, and now want to make sure the motor is turning the correct rpm.

We will connect these to the Arduino as such:

E (emitter) to GND
C (collector) to a digital input pin, and to +5v through a  10K resistor.

C (cathode) to GND
A (anode) to a 150 Ohm resistor, with the other end of resistor to +5V


 This project will entail the use of hardware interrupts, which the following video touches on. Code samples to follow soon.