How to improve my son's solar bobble head [closed]

Question

My son has a minecraft solar bobble head (in this case a bobble Steve). Under light it swings a diamond sword this exact one (Puckator Officially Licensed Minecraft Steve Solar Pal https://amzn.eu/d/gH1XvAn).

It is made up of a small solar cell, connected to a circuit board that holds a single capacitor and the board is connected to the copper coil. A magnet sits in a plastic housing that is connected to Steve by automaton connections and dynamics (photos can be added if needed).

It is dismal it barely moves under any light regardless of source (sun, room, phone, torch, plant grow UV). How can I increase its magnetic resistance? A better solar cell? A smaller capacitor? A smaller/larger voice cell copper coil? I've already tried swapping out the magnet for neodymium button magnets but it seems the issue isn't in the strength of the magnet

Ps. I know it's silly and probably never worked in the first place but me and my son are going to fix it or make it better, so any suggestions aren't wasted they are all in the name of my son learning electronics and physics. (He's 8 and rather ahead for his age.)

Answer 1

magnetic resistance

I know what you mean, but that's not really a term in widespread use. Electromagnetic force would be quite descriptive instead.

a better solar cell?

Yes, definitely. A larger solar cell would help. The square ones you'd find on top of solar lights should be sufficient for this.

a smaller capacitor?

Not at all. The bigger the better. But of course it will take longer to charge up. I'd leave the capacitor unchanged for now. There is a possibility that the capacitor itself is bad (electrically leaky). But I wouldn't replace for a larger capacity value. Leave be for now.

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It's likely that the toy doesn't have an "undervoltage lockout" and wastes energy that way.

Solar toys that have insufficient solar input to work just off solar power - and this one is of that kind, due to a very small cell - need to first charge up a capacitor from the solar cell. Once the voltage on that capacitor is high enough, the "motor" is turned on and the toy will "run" for some time.

There are modern, single-chip, ultra-low-power (they don't use much electricity) voltage monitors that can be used to detect when a capacitor is charged up high enough and turn on the electromagnet and its driving logic. Such a chip uses so little power that it won't be discharging the capacitor while the latter is charging up ("soaking up the Sun").

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I'm sure the toy is salvageable, but how much reengineering it will need is anyone's guess unless they opened a similar toy before.

Perhaps getting it to work from a regular small battery - say one or two AAA cells, so 1.5V or 3V - would be a good starting point. Just to make sure the thing functions at all. Only then will it make sense to mess with the solar cell, capacitor, etc.