Reverse Engineering a Wind Up Torch
In order to gain a better understanding of current crank chargers on the market, I decided to take apart a wind up torch. This torch did not have a phone charging plug but I remember previously owning ones that did (and them never being particularly successful at actually charging a phone…).
Having watched Youtube videos of such torches being adapted to phone chargers, I found exactly what I expected, quite a complex gearing system and a small motor. Building a gearing system was something that I toyed with in the last few weeks for my kit but gears are very hard to build (especially when there is quite a lot of torque involved).
For the circuitry, there was a voltage regulator, a battery, a capacitor, a button, LEDs… On the other side of the circuit were resistors and mysterious M7 chips.
I tested the voltage coming out of the motor and was surprised to see that it went up to almost 7 Volts when I wasn’t spinning it that fast!
I next tested it after the voltage regulator and was happy to see it limited to 5V. I could probably adapt this torch into a phone charger as they’ve done on Youtube then!
Finally, I tested the voltage just as it went into the LEDs, it was coming out at 2.6V steadily (with the LEDs turned on). I can presume this is because of the battery in the circuit and that that was how much charge it had.
The one thing I still don’t understand is the role of the capacitor, and why it is necessary with a battery in the circuit anyway.