Introduction: 4-up Wireless Qi Charger
The charging station is laser cut from plywood of varying thickness and polyethylene, then assembled with a hand full of stainless #2 x 3/8" and #4 x 1/2" flat head, sheet metal screws. A 60W CO2 laser is sufficient
Baltic Birch plywood in 3mm, 6mm and 9mm thickness. This plywood is light in color with flawless surfaces, from:
1/16" thick polyethylene is impact resistant and translucent.
I also added a power indicator blue LED, 5mm to match the charger LEDs. A 150 Ohm 1/4W resistor limits the current. Any electronics supplier such as Digikey or Mouser will have these in stock.
Step 1: Wireless Qi Charging Station
At the SWEETLab (Sustainable Water, Energy, Environmental Technology Lab) at Portland State University we developed a wireless data logger to be deployed on a variety on research projects. The SWEETSensor can be customized with a variety of sensors and reports through either GSM cellular or Iridium satellite networks. To minimize ingress we equipped the instruments with wireless Qi chargers since many wind up in hot, wet, dusty, outdoor environments where a USB plug would be a liability.
For larger deployments I built this 4up charging station utilizing the Adafruit Universal Qi Wireless Charging Transmitter;
To power the four transmitters I found 5V / 8A power bricks at Surplus Gizmos in ready supply, uniV Power P/N: PS-5080APL6A
Step 2: Air Cooling
Since Qi charging is only about 50% efficient some heat is generated. To aid in convective cooling the back and bottom faces are notched. Also on the back is a convenient cable storage compartment.
Step 3: Attaching the Leads
Solder 10" of flexible hook up wire to either side of the input capacitor, the bar side is positive. Wire size is not critical, anything between 26 and 22 GA (0.25 and 0.6 mm2) will do.
Step 4: Assembly: LED Mounting
The blue LED leads are inserted through the back panel. On the other side solder 6" of red braided wire to the long leg of the LED (the anode) and the 150 Ohm resistor to the short leg (cathode), then add 6" of black wire. Slip shrink tubing over both solder joints to cover all bare wire.
Step 5: Placing the Chargers
Assemble the front bezel, polyethylene backing and the charger mounting plate with eight #4 screws.
Place the Qi chargers in the cut outs and attach each with four #2 screws. Place a 1/8" foam backing on the backside of the ferrite plates. This pushes them forward against the polyethylene sheet.
Feed the lead wires through the back plate.
Step 6: Back Side Assembly
Sandwich the the flat assembly and secure with 13 #4 screws.
Add the power supply, feed the LED and outer charger leads through the opening in the triagular piece and connect all the positive wires using a crimp contact.
Step 7: Final Assembly
Place the internal parts in the cut outs, with the small triangle cover the opening with the cables.
Place the side and back boards and fasten with #4 screws where the screws are perpendicular to the grain and #2 screws where the screws go into the cut face. Using the smaller screws reduces splitting of the face.
Step 8: DXF Files for All Parts
These are the DXF files that I used on our laser cutter. Red is cut lines, blue is engrave.
Modify the Registration plate to fit whatever device you want to charge.
Step 9: Singles
For smaller deployments or for the road I also build one-up Qi chargers, but that's a different project.