IR LED Emitter and Detector sensor array
|IR sensor array Fritzing file: ir_sensor.zip||21.04 KB|
This is an on-the-cheap (at least cheap by Radioshack price standards) IR sensor array that could be used for a line-following robot. Although there's nothing particularly revolutionary about this component, I figured I'd post it on LMR with my Fritzing file in case anyone wanted to be able to print out the PCB pattern to etch their own.
- 3 Radioshack infrared emitter and detector pairs (part #276-142)
- 3 150 ohm resistors
- 3 10k ohm resistors
- header pins/connectors (optional)
The general princple behind the sensor array is fairly simplistic. Radioshack's IR sets are essentially an infrared LED paired with an infrared photodiode. The 150 ohm resistor simply limits the current that goes through the LED, whereas the 10k ohm resistor limits the current released through the photodiode.
Note that in the diagram above, the photodiodes are represented as LEDs. That is simply because Fritzing does not have the exact part, and as such I've simply represented it as an LED.
You can print out the circuit using the enclosed Fritzing file for the PCB layout. There are a wide variety of tutorials on the internet about methods for printing your own circuit board, but I found this tutorial about PCB etching to be most useful. If for whatever reason that link ever becomes broken, or if you'd like to find other methods an tips, Google for "etch a pcb" and you'll get lots of info.
If you use the attached Fritzing file, you will end up with something like this:
And as a real-life thing:
A few tips from the school of hard knocks:
- The Radioshack IR pairs are somewhat confusing, in that the IR LED and the detector kind of have "backwards" pins. On the IR LED the long pin is the positive side, whereas on the detector the short pin is the positive side (it was labeled as the "collector" on the diagram on the back of the package I got.)
- I used little pieces of wire shrink tubing around the IR pairs in order to attempt to isolate the light from each sensor. This did seem to have a noticable albeit small effect on the accuracy of the readings.