High-power switch LM324
Electronic

In this project, you're going to use two keys to measure your kinetic energy and indicate it on LEDs. The LEDs will work in a manner similar to a bicycle headlight, which shines brighter you pedal faster.

When you finish wiring, turn power ON. Press the keys S1 and S2 alternately with your finger tips. (You can repeat simultaneous pressing of the keys if you wish.)

As you speed up the pressing action, you'll see LED 3 light up, then LED 2, and finally LED 1. You may be sweating when all LEDs have lit. Try hard!

S1 and S2 are connected to the same CR differentiating circuit, which produces a differential wave with each pressing of a key. This wave passes through a diode to charge C3. Because C3 is designed to discharge through R5, raising the voltage in C3 requires you to press S1 and S2 frequently to add electrical energy to C3.

U1 A, U1B, and U1C are comparators with their own thresholds. As the voltage in C3 goes higher, the comparators turn ON one after another to illuminate LED 1, LED 2, and then LED 3.