Let's Make Robots!

Dead-reckoning on the cheap

Evening all.

Im thinking about adding some dead reckoing to my Differential drive bot, currently named "Cyclops", but to soon to be changed to "Minotaur" for reasons im sure you can work out!?

I did have an old mouse, from which i scavanged some IR thingys, but due to not checking what they were or how they worked first, ive burnt (at least) one of them out.

Also, example code looks unecesserily complicated to me!

Here is the bot, naked: 

The wheels already have some little stripes cast into them, but i was hoping to do it with what i have already.

therefore, at the cost of resolution in the movement sensing, i was thinking i might use YET MORE Photo resistors. (every last sensor on the damn thing is a PR at the moment, doing all sorts of things).

I was thinking i would either drill some holes through the existing sensor track, or just mount the PRs just on the inside of the spokes of the wheel.

Then, assuming there is reasonable ambient light, and the PRs are situated close enough to the wheel, the PR can then be used to "count" the rising , falling, or even both, edges of the wheels as the spokes pass in the way. (5 spokes, 10 edges)

if there is not sufficient ambient light, i could always mount some LEDs just above the wheels to provide the light!

considering PRs are pennies, and proper encoders are around $10, has anyone else done this.

does it have legs, or is there a reason this wouldnt work i havent thought of?


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Photoresistors are slow. It might take as much as a tenth of a second for it to adjust from low to high scale.
That doesn't mean you couldn't do it but you would have to have a slower rate of turn on your wheels to compensate.
Robots that move too slow can be boring.