Wireless power transmission circuit

[gengis]

This circuit cries out for a picaxe application. Simple cheap with a transmit range of 10 cm.

13 MHZ transmitter circuit uses a cmos hex inverter driving a pair of cmos switching transistors exciting a tuned series resonant coil.

The receiver is just a parallel tank circuit, full wave bridge and shunt regulator charging a small cap. He shows 1N4001 diodes but at that frequency and power level, 1N914 or 1N4148 should work better. Unfortunately, he doesn't specify power transferred.

Design Idea
Wireless "battery" energizes low-power devices
A simple 13.56-MHz oscillator broadcasts power to a receiver circuit.
Carlos Cossio, Santander, Spain; Edited by Charles H Small and Fran Granville -- EDN, 11/22/2007

http://www.edn.com/article/CA6501085.html?spacedesc=designideas&industryid=44217 whole article (~65kb)
Schematics:
http://www.edn.com/contents/images/6501085f1.pdf transmitter circuit (45kb)
http://www.edn.com/contents/images/6501085f2.pdf receiver circuit (35kb)

 

[BeanieBots]

Nice and simple. If anybody does build one I'd love to know the power transfer at 10cm range.
I'd also like to know if 1N4001s really would work at that frequency.
I'd go straight for a 1N4148 or similar as suggested above.

 

[gengis]

The author uses a crystal and 13 mhz - but the basic idea with almost no modification should probably work pretty well as an untuned transmitter (no crystal) and receiver to transfer power across a plastic divider for instance. Half a cup core on either side, or ferrite rod that slips into a cylindrical cavity (that should be very efficient coupling) so you could charge batteries without opening the case or depending on corroded contacts to make a connection.

Great for a waterproof application, but won't cover any distance to speak of.

 

[manuka]

There's nothing new about wireless power transmission,but (as Tesla demonstrated in the 1890s) overall efficiency is low. Do a Google on his amazing brainstorming! If you live near a strong broadcasting station a crystal set is akin - I've heard of folks lighting Xmas tree LEDs thanks to a kW level transmitter just over the back fence! Exploiting such low grade electrical resources is known as energy scavenging - a fascinating field in fact.

Electric "cordless" toothbrushes often use an induced EMF charging technique, but the gap is only a few mm & the lengthy charge times imply maybe only a few mA being handled. Although this may just be enough to run a PICAXE, a small PV (perhaps lifted from a coin shop calculator or solar garden lamp) would make more sense. For starters it's output voltage will be higher & you'd also get DC! Although naturally best outputs come from bright sunlight,even ambient room light will give a few mA at a few Volts. Stan