Hello I need help figuring out the coil structure for a toy I want to build. I have a rubber ball with a battery inside. I want to recharge the battery without a galvanic connection. I'm looking to get about
300 ma charge current. The ball will sit in a cup shaped recharger. And the coil in the charger will be powered by a wall wart with a nominal 12 vac output and around 500ma or less. What I need is help in figuring out the shape of the coils and their positions and the number of turns and so on. I am fairly good with most electronics but never could grok this inductive stuff. The math is above me. If I could just get a bit of advice on some basic aspects like for instance:- Would the coil shape for the charger cup be better as a say 1.5" donut shape mounted in the bottom of the cup just below the surface with the other coil in the ball just above and stacked like two donuts, be better than a 3" coil in the rim of the cup with the ball's coil like a smaller donut in the hole of the larger charger coil's donut?
- How do I determine the number of turns I need to limit the current drawn from the supply to it's rated power output. assuming 60hz at around 12 vac?
- I would prefer an air core but it would be nice to know if that was a mistake.
- given the coil on the primary side is x turns what should the coil on the secondary side be. I need 5 volts or more at 300 ma or so. To run the ciruitry and have the over head to charge the battery.
- How can I predict the effect of seperation on the power exchanged by the two coils? I would like at least an inch between them is this feasible? And if not what number should I use?