12C508 IR Obstruction Detector

This project is inspired by the DPRG IRPROX project. They have a pretty good PCB layout and idea. I would like to thank them for posting their project for all of us to see and learn from, I wouldn’t have started PIC programming without them, or at least not nearly as quickly come up to speed! The pinout on my board allows either a five-wire or a four-wire connection to be made the former uses a disable line if desired. You can also put in a resistor or use a trimpot to adjust range. The trimpot locations are very generic, most pots will fit. Be careful not to adjust pot to 0 ohms!

The IR proximity detector works very well, even in a brightly lit “noisy” environment. Instead of modulating the IR LED for 600us and then looking for a detection, I now look for a detection after every on/off cycle of an IR LED and count the number of hits that I get. I also look during the ‘off’ cycle when none of the IR LEDs are on and count the number of false hits that I get there. If I get more good hits than false hits then I say its a true detection. I then increment a counter as a sort of timer, when it passes a certain threshold, I notify a hit. At this time I check to make sure that a minimum number of good hits has been attained. At the same time I keep track via another time-out counter of noise hits. When this counter passes a certain threshold it then removes any detection that has been set. I fiddled a lot with the various threshold values for minimum number of good hits, time-out values and divisors for updating the false hit counts, and finally settled on the ones that currently used. I’m calling it a success and moving on to other projects! The source code for the, uhm, DLC IR proximity detector can be downloaded below as well as the PDF documentation for this kit.

I am now selling the complete kit, it was brought up to me that the exorbitant shipping costs from some distributors makes a full kit a real value added. So, here it is. The board, PIC, LEDs IR components and resistors as well as instructions are for sale. . I will make this in either 38KHz or 56.7KHz models. [url=mailto:dlc@verinet.com]Contact me[/url] if you areinterested. Bulk buys of 10 or more or robotics clubs get discounts!

Copyright 2006 [url=http://users.frii.com/dlc/robotics/botlinks.htm]DLC[/url]Parts:This kit uses either the Panasonic 4612 or 4614 IR demodulator.

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