This Instructables shows how to reuse old USB battery pack power some tiny tools.

Step 1: Why?

I found many old USB battery pack when I tidy up my room. It mostly come from gift and souvenir. Their capacity often very low, and mostly only can output 500 mA, It is hard to treat it as a backup battery for the current mobile. But I think the old USB battery still can power a bunch of tools.

The first tool I would like to make is a tiny screw driver. When I repairing my gadgets, I need to screw in and out tens of screws, but I don't want the high torque of a normal electric screwdrivers hurt the tiny screws. So I want to make a tiny screwdriver to help me the screwing work.

Step 2: Prepration

USB Battery Pack

Don't buy a new one, just find some in your drawers.

Interchangeable screwdriver set

something like this: https://detail.tmall.com/item.htm?id=520149044454

USB Type A male break out board

For getting USB power.

N20 Micro Metal Geared motor

1:298 gear, 3mm or 4mm D shape Axle.

Axle Shaft Coupler

The size depends on your screwdriver set adapter and motor Axle.

6 feet 3 files ship switch

For switching motor rotation direction.

Screws

2 M3 x 6 mm screw for fixing USB breakout board; 6 M3 x 8 mm screw for assembling the case.

Step 3: 3D Print the Case

Just print both side, a and b, with your 3D printer default normal or low quality setting is good enough.

Step 4: Patch Screwdriver Adapter

Cut the screwdriver adapter and connect it to the axle shaft coupler.

Step 5: Connect Motor

Connect the other side of axle shaft coupler to the Motor.

Step 6: Soldering Work

Connect USB power to the ship switch middle feet
Cross connect left and right side feet of ship switch to make a motor direction control circuit
connect motor to the ship switch right side feet