# making small ac for wireless power transfer !

Hi
As i understand i need PWM or AC for transferring power from an coil to another. How can i make a circuit for that? I just want my Arduino to power up or charge once i drop it on the coil !
How can i generate AC for that purpose? As i know for converting ac to dc just needs 4 diodes. So i don't have a problem on the receiver.
I got an wireless transfer module my self. It has 2 ICs on the transmitter. i don't know why it needs that much. the receiver also regulates down to 5.22v so i guess the other stuff are for that ! but i want to make my own.

Have a look at a electric toothbrush. It is basically a transformer. But transformers only work over very short distances but i believe that is ok for you.
A transfomer gives a ac voltage that is 4,44BANf where B is flux density in teslas, A is the area of the magnetic path in m^2, N is the number of turns and f is the frequency. When both the primary and secondary windings are close coupled B*A is the same in both windings and can be dropped from the equation. When the windings are apart from each other B will be lower in the secondary so the normal transformer ratio no longer holds. When designing a device like this you have the choice of either using a iron core which increases the inductance and thus lowers the idle current. In this case you can use the 50Hz (or 60) mains frequency. If you want to skip the core you will get a much lower inductance which means you will have to use a higher frequency.

nilton61:
Have a look at a electric toothbrush. It is basically a transformer. But transformers only work over very short distances but i believe that is ok for you.
A transfomer gives a ac voltage that is 4,44BANf where B is flux density in teslas, A is the area of the magnetic path in m^2, N is the number of turns and f is the frequency. When both the primary and secondary windings are close coupled B*A is the same in both windings and can be dropped from the equation. When the windings are apart from each other B will be lower in the secondary so the normal transformer ratio no longer holds. When designing a device like this you have the choice of either using a iron core which increases the inductance and thus lowers the idle current. In this case you can use the 50Hz (or 60) mains frequency. If you want to skip the core you will get a much lower inductance which means you will have to use a higher frequency.

yes i don't care about distance, i basically want to avoid plugging in, thats all !
i have to google about flux and other stuff (i know what they are but forgot how to calculate them :))
i think im going with air core (i will also try the iron, but how exactly should i use that? put the receiver on the core like toothbrush??!

And how can i generate that 50Hz-60Hz AC?

You donâ€™t need to generate 50 or 60 Hz ac. Its already in your wall outlet

nilton61:
You don't need to generate 50 or 60 Hz ac. Its already in your wall outlet

:o so i only regulate it to 5v on the receiver side? im worried im gonna kill my self with this 220v ! my father won't allow me to do it :D. anyway to generate it for the transmitter from a 9v battery or something? like the kit!

You have to rectify and regulate on the receiver side, yes. If you scrap an electric toothbrush (just the brush, leave the charger as it is) you can do this safely.

nilton61:
You have to rectify and regulate on the receiver side, yes. If you scrap an electric toothbrush (just the brush, leave the charger as it is) you can do this safely.

but what if i wanted to make the transmitter myself? im just looking to learn, if its too hard im not gonna try to make it!

In that case you have two options: