Let's Make Robots!

Adventures in Robotics, Numbers count

Today I was busy trying to interface an infrared detector to a PICAXE 28X1 on a project board.  My goal is to integrate this into my first robot, Ajax, so he can receive commands from an TV remote control.

The PICAXE documentation shows the 3 pins on the dectector wired to a a couple of resistors and a single capacitor, how hard could it be?

Two hours, later I am getting nothing on input pin0 at all.  Zero, Zilch, Nada.  Nothing.

The irin command never seems to return even though I give it a timeout value and a label to goto on an error.

After a while I realized that the IRIN command was ...never coming back... which seemed very odd.

Doing a bit of googling I found an article saying it could be caused by a noisy signal.  At that point I disconnected my IR sensor entirely and just tried to apply 5 volts to the input pin.  Concerned about shorting my board/chip I pushed this through the 4k7 resistor I had been using and got ...nothing.

It was bad enough I couldn't get the IR detector working but now it looked like I couldn't even read a button press on an input pin???

I finally used a short block to short the pin to 5 volts and SURPRISE it worked fine.

I was confused and then looked more closely at my resistor.  It turns out I was using a 47,000 ohm resistor not a 4,700 ohm resistor.

It appears that "numbers count" ...LOL.

The battle resumes tomorrow, one mistake down, more to go....LOL.



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My soldering techniques need much work, but tonight I got the components onto a PCB and working.  All I have to do now is drill a few holes in poor Ajax and Robot #1 will be ...remote ...control.... <add evil laughter here>....

OK, I went down to the store and picked up some 4k7 resistors today.  When you use the RIGHT resistor (as opposed to the 47,000 ohm resistor), the IR detector works on the PIXAXE 28X1 just fine.  Joy, joy ...happy dance.

I can now solder the pieces onto a small PCB, screw this onto Ajax and the IR remote control commanding can begin.

Sometimes you lose ... sometimes you win!



Thanks for sharing. :)

Good idea to write this down. I am sure that everybody already had such an experience but did not come out with it. Numbers are important, especially in electronics. Milli, micro, nano, kilo or mega...huge differences and huge impact on the result.