Wireless Power Transmitter and Receiver

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.

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.

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.

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.

Here is the 1:1 photo plot of the PCB design in PDF format.

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.

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

Have fun!