# Wirless Power

I posted another topic for the programming of this:http://arduino.cc/forum/index.php/topic,87218.0.html

Skim the other topic before reading my question or else it will not make too much sense.

Now I have a tone running through a motor driver shield. If I hook up a speaker to the secondary coil I get the ax act same tone I am running through the shield. My problem is this tone is loud, but will not light an led even if I convert it to dc with a diode. How do I go about solving this problem?

The motor shield is an H-bridge, in audio terminology BTL for balanced transformerless, meaning both lines are actively driven outputs. You may be trying to light up your LED from an output being driven to the opposite supply rail you have the LED connected to.

I'm not entirly sure what your saying, but how do I fix it?

Make sure there is a resistor of at least 390 ohms in series with the LED, discard the one you have odds are you flashed it. tie one side to Motor channel + and the other to motor channel -. whether or not it lights will depend on direction. Reverse leads as necessary.

I have a hefty 5V led which does light either direction on the motor leads, what is not happening is it is not lighting on the aecondary coil, but I can get a tone on a speaker.

secondary? are you driving a transformer?

@N314

I read the instructables about the project you planning to do. The principle is a transformer without the metal / ferrite core. The Ardiuno can generate the frequency you want. Bear in mind it will be a square wave. So the square wave has to be filter and than drive a push-pull configuration to apply the frequency wave toward the primary. The code to generated a frequency is simply a blink ( on / off ) but you have to calculated the time ON and the time OFF using this : t = 1 / f 50 % duty --> ton/off = 1/t

So a motor shield will not cut it. So use power transistor / MOSFET to drive the primary coil. Most inverter circuit ( 12 V to 120 V ) I saw use that principle. So it just might work. You have to do experiments to find out...

Well ive technically gottten it to work. I use the motot shield with a tone() on the directio pin. What it is now is NOT a picture ov effiency. I put 5v to the primary, and get (if im lucky) .5 volts off a capacitor attached to a diode in the segondary. I wall try the transistors to see if that somehow does somthing the motor shield does not.

One interesting thing I have observed though is that when the coil was running, a totally unatached piezo element near the coil started making the exact same tone I was running through to coil.

A switching power supply on a bare minimum runs at 30KHz to upwards of 150Khz. The transistors in the Motor3 have too long of rise and fall times to be used as power supply choppers. Unless you use an 60Hz transformer.

One interesting thing I have observed though is that when the coil was running, a totally unatached piezo element near the coil started making the exact same tone I was running through to coil.

It appear you got it working...some how... Piezo buzz without wires... :open_mouth: