74*245 Motor Driver

H-Bridge Driver

Simple PWM Gen.

Handy Method Measuring RPM

Measuring RPM via Photo reflector

Introduction to Robotic

DC, Stepper,and Servo Motor

Microcontroller Tutorial

Computer Interface
Tutorial
.............more links

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And a parts list...
2 X Panasonic 1381J 2.6V-2.9V Voltage detectors (digikey part # = MN1381-J-ND)
These voltage detectors come in many different voltage ratings. If your motor is spinning too hard, losing traction with the ground, you may want to use a 1381G (2.4V-2.6V) or 1381E (2.2V-2.4V). If you want more power per step you can use the 1381L (3.0V-3.3V) although it will take longer to charge up.

2 X Photodiodes (digikey part # = LT1032-ND)
I'm not positive on this part number. I got a big box of photodiodes for free so I haven't ordered these specific ones.

2 X .22uF capacitors (digikey part # = P4958-ND)

2 X 2N3904 NPN transistors (digikey part # = 2N3904-ND)

2 x 2N3906 PNP transistors (digikey part # = 2N3906-ND)

2 x 2.2K ohm resistors (digikey part # = 2.2KQTR-ND)

1 X 4700uF eletrolytic capacitor (digikey part # = P5118-ND)

1 X 100K ohm potentiometer (digikey part # = 3386H-104-ND)

2 X Pager motors or small tape recorder motors. They have to be efficient. I suggest the Solarbotics pager motors. The Namiki 1701.

2 X Fuse clips. Or any thing you can use as motor mounts. (digikey part # = FO52-ND)

1 X Solarcell. Any solarcell that can output atleast 3.5V will do. Solarbotics has the best high-current solarcells around.

Next I suggest you breadboard the circuit just so you know all your parts are good and my schematic is right! ;)

Test the circuit by approximately centering the potentiometer and throwing the circuit under a light. One of the motors should be spinning (popping). Cover one photodiode then the other with your finger. Do both motors spin? If alls good then you can build your photovore.

There are many ways you can build the photovore circuit. My favorite is free-forming.

First off, glue the two 1381's face to face. Then glue the two 3906's together and the two 3904's together and glue them all into one block. This block arrangement is ripped off from Paul Beckingham ;-) .

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