Don't fear the 50/60 Hz noise - Use it

I am sad to say that I do not get much time to build any robots these days.. However, every now & then I get a few moments in my workshop.

Thanks to OddBot I got myself some phototransistors a while back, and now I had some time to play. I was thinking of making 2 robots send little signals to each other via a light beam.

Unfortunatly it's winter time in Denmark, and so I had to work under indoor light bulbs. And as you may know; Working with pulsating light under a such can be a pain!

So I thought.. hey - if these 50 Hz are so over all dominant, and the darn phototransistor, hooked up to a Picaxe spinning 16 MhZ is so happy to pick up this "noise".. well then, why not make use of it?

So I just used a phototransistor, and wrote a few lines of code that I thought would be really "bad" for what used to be a problem.. and ended up getting myself a new sensor with an amazing thin beam, working at up to 40 CM's - as long as the target is hit by a light from an indoor lamp :)

I haven't done much testing on it, have little time, and want to do something else.. however, thought it was a quite funny thought; Let the "lightbulbs" work as a "sub-carrier" instead of trying to avoid them :)Perhaps one of you out there have more time, and wants to pick this up?


Readadc10 (read analouge in with high resolution), have a light bulb on, and read the numbers that you are getting. They are extremely steady, so the rest should give itself - the sensor could be programmed any way you'd like..


Very cool. You misspelled
Very cool. You misspelled analog though… Could be interesting as a sensor to detect movement. When it sees movement it wakes up for a few minutes then goes to sleep mode until someone else moves in front of it. Like a pet… when you coem home its happy. When you aren’t around it gets sad and sleeps.

Dan, TheCowGod, have you
Dan, TheCowGod, have you read jklug’s comment? sounds like a project for you :wink:

Fasten your Helmet?

I think it means do up your zip



One way or another





Hmm, good point, I’ll

Hmm, good point, I’ll definitely have to take a look at it, might be just what I need.


This was on my list of stuff
This was on my list of stuff to do when I get time. I also wanted to make a recharing station. My thought was to have it send out an IR signal when it needed power. The IR signal would be received at the charging station and turn on a red laser beam that the robot would detect using a photoresistor mounted at the same height. It would then drive toward the laser and line itself up to charge. When the charger got the batteries to full it would pull away from the robot and the robot would resupply power to the brains and it would reboot ready to start all over. Of course I would need to learn recharing circuits so I didn’t burn batteries… :slight_smile: