A simple desktop spinner using the Miller engine. It uses a 2.2µF timing capacitor and an MCP112-270E that triggers the circuit at 2.63V, powered by two solar panels in series providing 6V.
The Miller engine is one of the simplest, most robust solar engines around. Like the FLED solar engine, it uses a voltage-based design, but rather than using a flashing LED to determine the trip level, the Miller engine uses a dedicated voltage supervisor IC. This makes it a lot more power-efficient and easier to build. The voltage trip level can also be customised based on the variant of the IC used. By adjusting the size of the timing capacitor across it, you can also configure how long the circuit activates for. The bigger the capacitor is, the longer the circuit stays on.
The original Miller circuit uses a 1381 IC, which is now discontinued and hard to find. Fortunately, the more widely available MCP112 voltage trigger can be used as a drop-in replacement. Apparently the 1381's cousin, the TC54, could be used in this circuit as well, but I've had no luck with that. There are two types, the TC54VN and the TC54VC. I tried a TC54VN, so it may be that the TC54VC is the one that works.
