Light powered LED circuit

[Nick Sullivan]

HI,

Please see attached.
I’m looking to use a photo-voltaic cell and 2 inductors to use light to wirelessly power an LED. I don’t want to use any other power source (battery, mains, etc.). The schematic shows a DC source (photo-voltaic cell) in parallel with a capacitor and an inductor. The second inductor would ideally be an inch or so away from the first, connected to a bridge rectifier, which provides DC current to an LED. Again, the important thing is to be wireless (2 inductors) and to be only powered by light. So, if I were to walk in a room and flip on a switch, the LED would come on. If I flip off the switch the LED turns off. The only confusion I have is on the photo-voltaic side. I’m not sure how to use the photo-voltaic cell to create a constant AC signal for the inductor. Help please.

 

[KrisBlueNZ]

Hi Nick and welcome to Electronics Point

You need some kind of oscillator. There are many options. But I don't think your project is feasible.

First, photovoltaic cells are not very efficient and cannot generate much power unless (a) they are very big, and (b) they are in direct sunlight. If you have your photovoltaic cell, put it under your room light and measure the open-circuit output voltage, and the short-circuit current. You can't calculate the output power by multiplying those figures together, but they will give you a very rough idea of how much power the cell can supply. If you post them here, we can tell you how to make a more accurate measurement using a load resistor.

Second, with a one inch gap between the two inductors, you will lose a huge amount of power, and probably more than 99.9%. I don't know how to calculate it, but my gut feeling is you will lose more than 99% of the power. This is why cordless chargers require closely mating surfaces.

If you tell us more about your project, including specifc component part numbers, we may be able to be more specific.