infrared ranging using custom solution?


Thread Starter

john d

Ok, I have been reading about designing this sensor, there will be 2, 1 for front and 1 in rear of bot. Each sensor will have TX for each 'corner' (IR led) and share a common RX (photo transistor). I want to be able to put as much of the required functions into a small pincount PIC, so figure it can be used for modulating the TXs based on the PIC's internal RC OSC, perhaps prescaler also. That part should be easy enough, and each TX LED gets fired at the determined freq in switched intervals.

The RX is a harder egg to crack tho--the resulting captured pulse needs to be treated to filter out noise, ambient conditions and most importantly other competitors! Although I also want to try and utilize other bots' IR to my advantage, that is beyond the scope of this posting... As I've understood the signal from the RX gets amplified, demodulated and then compared to generate a digital value for the main processor to use.

I figure I can use part of the PIC for the comparator but am still going to need a design the amp and demod circuit, and this is not easy as I have little analog design skills. So, anyone know of a better method which can utilize the PIC only to accomplish the same results? Or else any tips with designing the needed analog filter portions of the design? The rest I can likely manage with...

One thing I should point out: it's that I know nothing of my parts specs--they are salvaged components with no ID marks (photo trans and IR LEDs) but I still have their original PCB so can gather some info related... Any help appreciated!