Fun project idea: laser-guided robot

[elorc]

I know this has been done on a larger scale but I was thinking of playing around with something simpler. My idea was to try to build a simple little robot that follows the point of a laser. It doesn't have to be elaborate: even if it just follows the laser around a few inches in front of it, it'd be a neat little thing.

In doing some initial googling, I unfortunately only found a ton of hits on laser-guided military weapons which isn't what I'm looking for and is of no use to me.

Any ideas on a good starting point, resources, etc? I found some projects a while back that involved a robot that would walk in a path and change course if it contacted an obstacle. I'm not sure if I can relatively easily adapt something like that to work with lights/lasers.

Any guidance would be appreciated. :)

 

[schip666!]

You might be able t get a LegoBot line follower to do it, and let me _again_ plug
the Mark III robot which has some line following sensors included:
http://www.junun.org/MarkIII/Store.jsp
and a programmed PIC chip to run it.

The trouble is staying in front of the 'bot if you are thinking of shining the laser on the ground.

 

[K^2]

Actually, military laser-guidance system, when simplified to the basics, is not that complex, and you can build a robot that follows a laser dot without a use of MCU. Purely analogue design. All you need are a few parts you could even buy at radio shack and something to use for your bot.

First, consider a very simple light-following bot. Simplest design would use a platform with tracks, so that it's very easy to turn, but you can expand this design to a steering version. On the front of the bot place two photo-transistor "eyes". You want each one to have a slightly-overlapping FOV, but mostly to have one pick up light from one side, and the other from the other. Usually, with photo-transistors that have rounded caps, you can just point them at slightly different angles. Feed voltage from photo-transistors to a differential amplifier, and output of differential amplifier to the amplifiers driving the two motors. With the right bias on motor amps, it should be easy to make the bot turn towards the light.

Now the trouble with laser-guidance is that you can't make the laser dot so bright that it outshines all ambient light. But you can do another clever thing. You can modulate the light of the laser. Simply power the laser diode with AC at a fixed frequency. A simple low-high square wave should be sufficient. Now add an LC filter tunned to the same frequency after each photo-transistor. You might end up having to add a pre-amplifier before and/or after the filters to make it work, but ultimately, you do the same thing. Feed this to differential amplifier, and from there to motors.

With this setup, as long as the laser dot is in bot's field of view, and sufficient light intensity makes it to the bot's "eyes", it should be able to follow your laser's dot, and only your laser's dot.

The individual components you need here are fairly easy to find. If you look up LC filters, amplifiers, and differential amplifiers on-line, you should be able to find good schematics. All you'd have to do is put it all together.