Let's Make Robots!

Why am I an idiot and IR transistors...

Here's the encoder part http://www.sparkfun.com/datasheets/Sensors/QRB1114.pdf


This should be simple... resistor pulls the input pin high, transistor clicks and pulls it to ground.

What am I missing?!?!?



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Thanks man,

Naw, the idiot thing was the fact that I have wired basically this same configuration many times before and was just stumped why this time is was not working. --You know, a  "man, I gotta be missing something simple here..." moment. At any rate, all the encoders similar to this on in the past all just sorta "worked" with a "standard" 330r on the led and a 10k for a pull-up. Thus the "WHY ISN'T THIS WORKING!!??"  When I got to this one. Oh, and all my diagrams are just sharpie on typing paper, that and I still have to keep all my programming notes on paper (with a pencil) or I get confused. --We spend $6mil on a ball-point pen that would write in space, the Russians used a pencil.

In terms of processors and encoders for that matter, I am a picaxe guy (because the BASIC doesn't scare me and seems to work the best in my brain). With this encoder, and the final solution, I just needed to get the "low" low enough to break the picaxe's threashold of recognizing it as a 0. You nailed the idea of getting that LED brighter by the way, and thanks for the math lesson -it went straight to my notebook. I don't think I will need any amplification though, I did all my testing with the unit pointing straight up at a flo. light from the breadboard. When it is tucked in under the chassis 1/4" from the stripes on the wheels, I should have no problems at all. Not to mention, the tests were with typing paper and the stripes on the wheels wil be nice, high gloss paint and flat, dull black tire.

One more quick one (I don't want to eat up any of that 12gig of bandwith a month restriction you Aussies have) --That momentary idiot thing you speak of, well, it's a "brain-fart"... I don't know how universal that is.

Thanks for the help, as always...

Hi Chris,

 just call me Cliff,

A little point to note is looking at the datasheet (fig 5) you will get the best performance at around 1/8", at that distance the IR LED will be painting a disk 0.2" diameter so the size of the stripes on the encoder will need to be > 0.17" apart or they will start to interferr with each other.