# Hand Crank LED 'flashlight'

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## Introduction: Hand Crank LED 'flashlight'

This is an old school LED 'flashlight' that is powered solely on the mechanical input, which in this particular case is cranking the gearhead to turn on an LED. This is a perfect device when there is a brownout and you you're flashlights have ran out of their battery.

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## Step 1: BoM

• Unipolar Stepper motor
• 2 LEDs
• 2 Capacitors
• Popsicle stick

Tools:

• Glue gun

## Step 2: How It Works?

A motor converts electrical energy into mechanical energy, which is the motion we see when we supply it with some voltage. But a motor can also go in the reversed direction where it functions much like an alternator. It converts mechanical energy, by moving the gear head, to electrical energy. We then use this electrical energy to charge a capacitor and turn on an LED.

## Step 3: Connecting the LED

Connect the positive pin of the first LED to pin 1 and the second LED to pin 4.

Connect the negative pin of the first LED to pin 2 and the second LED to pin 3.

Note that the colour choice of the LED is important. The lower visible colour spectrum requires less voltage to power it, therefore, I chose red and yellow since have a longer wavelength. The visible colour spectrum is also known as the rainbow, ROYGBV.

## Step 4: Connecting the Capacitor

Connect the positive pin of the first capacitor to pin 1 and the second capacitor to pin 4.

Connect the negative pin of the first capacitor to pin 2 and the second capacitor to pin 3.

The capacitors will retain the charge and discharge it to the LED when it is not powered. Thus, as you crank, all the excess energy goes into charging the capacitor.

## Step 5: Making the Crankshaft

1. Glue the triangular popsicle notches to the shaft of the stepper motor with a hot glue gun
2. Glue to popsicle sticks perpendicular to the ones glued onto the shaft, one on top, the other on the bottom with a hot glue gun
3. Glue another pair of popsicle sticks perpendicular to the ones glued in 2nd step for the z-axis to make the crank handle

Crank away and power the LED!

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