Jan 23, 2011

Feeling my way

During the Christmas vacation I built a mobile robot using the Boe-Bot structural base and adding the Arduino 'brain' on top. This permitted me to rapidly get to the collision avoidance systems. I wanted to build my own range sensors since I started using with Lego MindStorm RCX 2.0 in 2000. I was always impressed by those guys on the web who were building custom sensors and accessories for their MindStorm projects.

The plan was to build an infrared range sensor that would be contained in a 2x4 standard Lego brick. I started by gutting out the Lego brick and drilled two holes into it for the LED and the detector. When positioning the light, I made sure it was set further back than the IR detector to prevent the LED light to shine directly into the detector.

I used the same parts than the ones I used on the Boe-Bot but I modified the circuit to make it more compact. Then it was the origami process of fitting all the components inside the brick and welding everything (including two resistors).

Wire wise, both the light and the detector needed a ground (black), the detector needed a 5v feed (red) and both were connected to separate control pins on the Arduino (yellow for the LED and grey for the detector). I then glued a 2x4 Lego plate to close the sensor.

Here is the final product attached to a servo. In this configuration I was able to sweep left and right, covering a wider range with one sensor.