Smartphones are a great invention, but a truly long- lasting battery is still a dream.
So my idea involves the integration of a power bank and a Wireless Power Receiver module FT1236M inside a normal woman’s purse (or a man’s one, of course), to always have a source of energy to charge your smartphone.
The charging of the power bank is obtained by placing the bag on a base that containes a Wireless Power Transmitter module FT1235M, powered by a common 5V 2A switching power supply.
With the available energy you can also power some “courtesy lights” LED, in order to find objects in the darkness.
You would also have more charging bases (at home, at office, in the car with an step-down adapter) or you can use the same base to charge more Qi compatible devices.
The Wireless Power Kit
The Wireless Power Kit I received from Futura Elettronica consists of an FT1235M transmitter module, an FT1236M receiver module with the respective coils and meets the Qi standards defined from WPC (Wireless Power Consortium) for inductive charging over distances of up to 4 cm.
The Charging Base and the Receiver
The charging base is a flat support for the transmitter coil and the FT1235M board, made of plywood (I don’t have a 3D printer yet).
I added a MOSFET as reverse polarity supply protection and a Touch Sensor as a switch to put the transmitter in very low power mode, saving further energy.
I replaced the card’s LED with two more visible ones, which I placed on the edge of the base.
The receiver consists of a small box (made of plywood), which is fixed on the bottom of the bag. The box contains the receiver coil, the FT1236M board, a 18650 Lithium battery, a charging module with protection circuit, a step-up module and a simple circuit to manage the courtesy LEDs through another touch sensor.
If used on a daily basis, it would be appropriate to protect the receiver box with a cover, while the transmitter coil should be covered with a thin plastic film having a hole in the middle of it, in order to correctly place the felt pad.
The Bag (let’s put everything together)
Inside the bag have been sewed the touch sensor, all the wires, and the two LED with associated resistors (fixed on little bits of perfboard).
The receiver box has been fixed on the bottom of the bag below the lining, with double-sided tape and they have connected the sensor and LED wires. The USB cable for charging the phone was left ouside.
On the bottom of the bag, on the outer side, it was attached an adhesive felt pad, in correspondance to the center of the receiver coil, to make the alignment with the transmitter coil easier.
How everything has been put together should be clear from the photos.
The Charging Base Schematic Diagram is quite simple.
A common 5V 2A switching power supply provides power to the transmitter. An Ultra Low On-Resistance, Logic Level MOSFET protects the circuit against reverse polarity (a diode would have an eccessive voltage drop). A Touch Sensor (TTP223-B based) can switch the transmitter to a very low power mode, setting the ENABLE pin to high level and turning the LED off. The operation of the touch module has been changed from direct to toggle according to the datasheet (TTP223-B pin 6 to high). From the FT1235M card the D1 and D3 LED were unsoldered, and replaced by normal 3 mm ones, and the resistor R15 (4.7K connected to EN input) as well, to further reduce the current consumption in low power mode. A resistor and two capacitors have been added to improve the stability of the touch sensor.
The Receiver Schematic Diagram is slightly more complex.
A PNP BC 560 transistor inverts the charging end low logic level signal from the pin 6 of the TP4056 IC (charging board) in order to properly drive the Charge pin of the FT1236M and stop the energy transfer when the battery is fully charged. When this happens, the blue LED on the base stops blinking, still remaining turned on.
A small signal MOSFET BS170 turns on the two courtesy LED when you touch the sensor. The capacitor on the gate maintains this state for about 10 seconds; afterwards the LED will gradually turn off.
The courtesy LED are connected before the step-up module and power LED have been disconnected on the touch sensor and the step-up board, to save energy.
Finally, a resettable fuse protects the circuit from external faults.
1 x Wireless Power Kit from Futura Elettronica
1 x 18650 INR LI 2600 mAh 3.7V rechargeable battery
2 x Touch Sensor TTP223-B module
1 x TP4056 LI-PO 1A charger module with protection circuit
1 x 5V USB out step-up module
1 x 12N6LE MOSFET or Ultra Low On-Resistance, Logic Level equivalent
1 x BC560 PNP transistor or equivalent
1 x BS170 MOSFET or small signal equivalent
1 x red LED 3 mm
1 x blue LED 3 mm
1 x 1N4148 diode
2 x high brightness white LED 5 mm
1 x 100 μF 16V electrolytic capacitor
1 x 22 μF 16V electrolytic capacitor
1 x 100 nF ceramic capacitor
1 x 330 Ω resistor 1/4W 5%
2 x 10 Ω resistor
2 x 10 kΩ resistor
1 x 100 kΩ resistor
1 x 1 MΩ resistor
1 x resettable 500 mA fuse
1 x female barrel power jack
Demo video and acknowledgements
Finally, a brief overview video of the project and a thank-you note to my daughter, who made her favourite bag available 😉