Pocketeer klundry recently posted an image gallery showing how to add a wireless charger to PocketC.H.I.P.! The project requires only a few minutes of soldering and, like Jose’s speaker hack, is a great project for beginning hardware hackers.
Qi wireless chargers come in many different form-factors but are all based on the same principles of electromagnetic induction. The system is made up of a transmitter (also know as a primary) that’s connected to a power source and a receiver (or secondary) that’s connected to a battery. Together they effectively create a transformer, except unlike most transformers that are housed in a single unit, this system has an air gap between the transmitter and receiver.
The transmitter uses the input power from a household outlet to energize a coiled wire in its circuitry. When current flows across the coil, it creates a magnetic field.
The receiver has a coil too. But this coil is used to take the energy from transmitter’s magnetic field and convert it to an electric current to charge the battery.
- Soldering Iron, solder, and protective eyewear
- Needle nose pliers
- Two lengths of thin-gauge wire
- Kapton tape
The Qi receiver that we had around the office was made for a cell phone and housed in fancy plastic with a USB-micro cable. We had to use an Exacto blade to cut away a bit of the plastic to expose the 5V and GND pads where the USB adapter connected to the receiver. Then we removed the adapter and finally soldered a thin gauge wire to the pads –one for power (yellow) and one for ground (green).
Your Qi receiver may differ, and that’s OK. Just identify which wire is the 5-volt (also called VCC) and ground (abbreviated as GND) wires on your Qi receiver.
Note: Anytime you’re soldering wires together or to a PCB, it’s a good idea to tin the wires. This term refers to the application of a dab of solder to the wire before you attempt to solder it to another wire.
Remove C.H.I.P. from PocketC.H.I.P. and unclip the bezel and rear enclosure from the PocketC.H.I.P. circuit board. Make sure your work surface is non-marking, so you don’t damage your screen and flip PocketC.H.I.P. over so it’s screen down.
Use pliers to disconnect the battery from PocketC.H.I.P., taking care not to tug directly on the wires but pulling on the plastic JST connector instead.
Solder the 5V wire from the receiver to the CHG-IN pin on PocketC.H.I.P.. The two ground–one on the receiver and one on PocketC.H.I.P.– should be soldered together too.
Make sure your wires aren’t too short! The receiver will end up attaching to the top of the battery, and the wires need to be long enough to route through the case flush with the PCB.
Apply a bit of double-sided foam tape to the back of the PocketC.H.I.P. battery and gentle press the receiver into it.
Only one side of the receiver will work with the transmitter, either the front or back. Most receivers will indicate the proper orientation. Unfortunately, the receiver we used employs confusing iconography. The large arrow akin to a shipping container “this end up” suggesting the rotation of the receiver matters– it doesn’t.
All that’s left to do is put PocketC.H.I.P. back together. Make sure you don’t damage any of the wiring you added during the case reassembly. Also make sure the PocketC.H.I.P. enclosure completely snaps together and that your Qi receiver isn’t in the way.
Now that you’ve fitted a Qi receiver inside PocketC.H.I.P. how do you plan to deploy your Qi transmitter? Will you make a custom stand and embed it or mount the transmitter underneath your favorite workbench top?