The design uses a 4mm diameter motor. They are commonly available, but without part numbers. The one I use has 13 ohm resistance and is 10mm long. A shorter one is available but has 36 ohm resistance and doesn’t seem to work as well with the given circuit parameters.
The motor is a press fit into the hole in the top of the cube. You might want to glue it in.
For suspension, I use a short piece of wire insulation as a collar, press fitted to the axle with a piece of nylon thread underneath it.
You don’t want a rigid connection from the motor to the earring hook, you want a flexible connection such as nylon or chain. The starting torque of the motor is low, you want the motor to wind up the thread easily, which then unwinds and turns the dangly part i.e. the motor housing et al.
An earring hook is available from a craft shop. Search for “jewelry findings.”
If your motor comes with an off-center weight, you can break it off with bolt cutters placing the jaws parallel to the motor axle. The weight is usually pot metal and brittle, whereas the axle is steel and not brittle. Bolt cutters apply much force but don’t move much. Wear safety glasses: when the weight breaks, it explodes. You might be able to carefully use ordinary diagonals, or a vise.
You must orient these components:
- the solar cells
- the diode
- the storage capacitor (polarized tantalum)
Note that the solar cells are intended for use as photodiodes and are marked as diodes but must be installed in the reverse of the usual diode orientation (like all solar cells, which are also diodes.) The base of the arrow of the diode symbol should be to the high, Vcc side!!! (This is a correction. My original post was in error, and said the opposite. See later blog about my debugging this issue.)
The design has components on a single side, so you can stencil paste it, place your parts, and reflow it in your toaster oven or maybe a griddle.
The motor leads don’t need to be oriented unless you care about which direction the motor turns (you want counter rotating left and right earrings.)