Simple Robot Knows Its Bounds

The [Dallas Personal Robotics Group] recently put together a set of tutorials for their members, including the build process of a table-top robot, they call the Tiny Wanderer. The bot can be constructed pretty easily, and is meant as an introduction to robot building.

The small servo-driven bot uses simple edge sensors to ensure that it doesn’t fall off a raised surface. The sensors were built using a small IR LED and photo transistor, which is partially isolated from the LED by a piece of shrink tubing. An ATiny micro-controller takes two measurements of the amount of IR light entering the photo transistor – one with the LED on, the other with the LED off. The difference of these measurements is compared to determine if the edge sensors are hanging off the side of the table. The logic used here is pretty simple – the difference will be high if the sensors are hovering over a surface, due to reflected light, and low if the sensors are hanging over open space.

The writeup contains templates for building the bot’s structure, as well as source code and schematics for all of the electronic bits.

Be sure to stick around to see a video of the robot in action.

8 thoughts on “Simple Robot Knows Its Bounds”

1. jimbles says:

OK, this is taking a sledgehammer to a walnut!
Why would you use a microcontroller for something you can do with an opamp!?!?!

2. therian says:

line flowers originally was design to teach students about analog logic

3. zerobitjack says:

… back in my day we only had negative voltage and the electrons went the wrong way….

You carpers are pathetic.

4. Haydon Ryan says:

It is over-engineering, but what I’d like to see next is mapping the extents of the desk, and cleaning the top of it.

5. This is a neat little project.
To jimbles, if the end goal was this little robot, you might have a point. But, this is intended to be built upon and the way they did it makes it very easy to tinker with and learn.

To therian, this is not a line follower. It ambles around a table and backs off when it finds an edge.

6. rusty says:

what’s a carper?

7. PaulB says:

As Ralph says, this is an example project used to illustrate a broader range of maker/hacker techniques, categorized as “how to build stuff that uses mechanics, electronics, and firmware using cheap or free tools”. The DPRG tutorials section has the first of three tutorials along that theme posted: http://www.dprg.org/tutorials/2011-02a/index.html Keep an eye on that space for tutorials on how to design with the ATtiny family, and a quickstart for designing schematics and fab boards using KiCad. We’re a robot club, so we chose a robot as an easy example, but the source code and design are easily hacked to other purposes.

Have you built your first robot yet?

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