Robots at Home

Summers are all about projects – like robot building! While I understand the theory of electronics, I’ve done very little hands on, and I have a mediocre intuition for it, so this is a good learning experience for me. Nothing too ambitious going on here, we’re just following along with the instructions for building a line-following robot from Cook’s

Robot Building for Beginners
. Here are some photos of the prototyping process to date:

breadboard with power switchTo start, we have just a simple switch on the breadboard to connect the battery to the buses and light an LED when the power is on (to left). No luck finding a breadboard-compatable switch for this, as you’ll observe. Just getting this to work was surprisingly satisfying – it’s a cute little switch that makes a cute little light go on!

breadboard with photoresistorsNext up, some photoresistors and a variable resistor to vary the voltage in the two paths through the circuit based on the amount of light on each side’s pair of photoresistors (to right). At this point, the circuit really isn’t doing anything; it is just set up for the next steps.

It all gets more exciting when a comparator and some LEDs get hooked up to the photoresistors to show which side is currently getting more light (below). It also allows one to use the variable resistor to balance the two paths through the circuit so that when both banks of photoresistors get the same amount of light, the same amount of voltage goes through both paths.
breadboard with circuit

Finally, transistors and larger banks of LEDs are added. Check out a movie of the circuit in action (link is to avi file)! The banks of LEDs are to the right – three yellow LEDs and three green LEDs. The two banks of photosensors are flanking the two “headlight” white LEDs at the far left. As the finger moves back and forth across the photosensors, blocking their light, the banks of LEDs alternate being lit up.

The next step will be to add two motors, one to each “side”. When actually mounted on a robot frame, the photoresistors will point towards the floor and indicate whether the robot has veered off of the line it is following to the differently-colored floor, and fire the correct motor to correct the direction.

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