I was working on a concept design which has a bunch of electronics in a box that communicates to a PC without using wires or battery. First thing I needed to do was to power the electronics so I looked for a wireless power transmitter design and I found one which is simple, at least in terms of construction, and works really well.
This is a wireless transmitter and receiver project. The transmitter is based on the "Witricity" series by "gilbondfac" (http://www.youtube.com/channel/UCmEVJT7zJ535HiOb1frvoHw) I can't say that the the transmitter is simple but I think it's an RF oscillator that uses its inductor as an antenna. I don't have detailed knowledge of of how it works. I designed a receiver that's powerful enough to run a small DC motor so my concept design that uses an Arduino, some sensor and a few other electronics should be no problem.
Step 1: Transmitter Schematic
The transmitter uses a BD139 transistor, a few capacitors, a resistor and 2 turns, 6cm diameter of #18AWG magnet wire tapped at the center. The LED is just a power indicator. It oscillates at around 2.4MHz and takes in 6-9Vdc with about 160mA current draw.
Step 2: Breadboard and Blurry Scope Shot
To make sure the design really works, I wired the transmitter in a breadboard first. I powered the circuit with 6Vdc and it draws 160mA. The transistor can get really hot so you need to attach a heat sink. The receiver is just 5 turns, 6cm diameter of #18 AWG insulated wire with one end connected to a 1N4148 diode to act as a half wave rectifier. The output is connected to an LED with a 0.1uF filter cap.
The LED lights up as I place the coils near each other. I took a photo of the coils with 2cm gap. The LED gets dimmer as you increase the gap. I also took a blurry photo of the scope when I connected the probe at the connector pin of the transistor.
Step 3: Receiver Schematic
The receiver coil is 12 turns, 6cm diameter of #18AWG magnet wire. This coil is just like the secondary winding of a transformer when you're making a power supply. It connects to a full wave bridge rectifier using four 1N4148 high speed diodes. 1N400x diodes don't work. The rest of the circuit is just a simple voltage regulator using LM317 set to +8.4V.
I get 28Vdc before the regulator. I just need 8.4V to power my Arduino. I wasn't able to measure how much power we can get with this design but I tested it using a small DC motor from an old CD-ROM and it's almost going to burn out the brushes so It's probably enough to power LCD's and small servo motors.
Step 4: PCB Design
Here is the 1:1 photo plot of the PCB design in PDF format.
Step 5: Assembly
After making the PCB's solder the components and connect the coils to the terminal blocks. Here are some photos of the transmitter and receiver assembled boards.
Step 6: Power Up!
Connect the transmitter to a DC source and place the coils near each other. I connected the output of the receiver to the Arduino Micro and it's working well even at 2 - 3cm distances.
Here's the BOM:
4 x 1N4148, CR1 CR2 CR3 CR4
1 x LED, DS1
1 x 0.01UF, 10%, 50V, C8
3 x 0.10UF, 10%, 50V, C5 C6 C9
2 x 1.00NF, 20%, 100V, C1 C2
1 x 0.22UF, 10%, 100V, C4
1 x 4.70NF, 20%, 100V, C3
1 x BD139, Q1
1 x 470, 5%, 0.25W, R3
1 x 1.00K, 5%, 0.25W, R1
1 x 2.70K, 5%, 0.25W, R4
1 x 5.60K, 5%, 0.50W, R2
1 x 1000UF, 20%, 35V, C7
4 x TERMINAL BLOCK, J1 J2 J3 J4
1 x LM317, U1