Introduction: Crank Flash Light

About: Happily married, self employed, full wood shop, some metal work as well as electronics, antique collector.
I wanted a reliable hand crank light that would not wear your arm out in times of need
A retro look was desired too

Step 1: Find a Good Stepper Motor

I found several stepper motors but they were either too big, or did not produce enough voltage at a slow speed
This one is from a scanner off a copier.
What makes it suitable are three factors, one it has gear reduction (increase from our perspective) this saves a ton of time, second it has two armatures stacked, these can be connected in series to double voltage(almost)
Third it's small and makes a solid 6 volts AC
At a slow crank speed

Step 2: Where Is the Current

A very easy way to find the highest voltage is to measure the various wires through a swing meter, I have both digital and analog but watching the needle swing is much easier to see what coil is putting out
In this case the red line was about half so I clipped it off

Step 3: What Kind of Current

What your getting from this little motor is a alternating current I have seen people here using un-rectified current it works but you are working twice as hard using only half the signal
If you don't want to make a bridge just use an old style filament bulb (that's if you were going to be using LEDs )

Step 4: Full Wave Rectifier

This is a very common full wave rectifier made from scrounged diodes
If this does not make sense just google there are thousands of pages about them

Step 5: Add a Crank

I wanted a sturdy crank I thought this is where it would break so I took my time
The red washer is to smooth operation
A step bit is almost mandatory

Step 6: Stick It All Together

This flash light was from the 1960's there is lots of room I plan to add a super capacitor when I place my next electronics order
The bulb is an led upgrade from Walmart
It keeps the retro look the crank is from an old mechanical adding machine
All I can say is when you are testing your motor if you can't get your LEDs to light with a flip of the rotor you are not going to be happy with how hard you have to crank