0-15V DC Power Supply

For $15 each student gets a kit, project box and binding posts to make his/her own 0-15V variable power supply. It uses a center tap tranformer with just two diodes. A voltage regulator maintains the desired voltage under various loads. The potentiometer provides a voltage divider action to vary the output. Electrolytic capacitors help take out the ripple. Each student has their own soldering station as show below.

The students become competent at soldering, circuit board assembly and even drilling the holes in their project boxes, but still have to sit back and think about what they're going to use this "black box" for! In our classroom, we've mounted our pencil sharpener which once required AA batteries to the top of the box. We can vary the speed with which the sharpener turns!

The power supply will run lego motors, toys and walkmen, although you can't walk too far with the cord plugged in!
The students have to mark their boxes around the knob with 3V, 6V, 9V, 12V and 15V. Even then, Jeff burnt out his old Gameboy by
accidentally using the
15V setting!

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