The Powers of Induction

Overview

The goal of our project is to create a wireless charging pad capable of transferring power from a base station powered by a Lithium Ion battery to a receiver system that outputs power to a standard port at 5 V and .5 A. The device will consist of a transmitter base and a receiver, each of which will house an inductive coil capable of coupling at close distances. Unlike many wireless chargers on the market, our transmitter base will be powered by a 7.4 V lithium ion battery, rendering our transmitter pad portable. Switching and power delivery will be handled by an Arduino in the transmitter pad. The Arduino will switch a MOSFET transistor at a frequency between 10-20 kHz to allow for the delivery of alternating current to the primary coil. A battery management integrated circuit will be implemented in the transmitter base to prevent excessive spikes in current or voltage across our lithium ion battery. In addition, a LM60 temperature sensing IC will feed into the Arduino to allow for fail safe mechanism should the circuit get too hot. The alternating current in the primary coil should in turn produce a varying magnetic flux through the receiver coil, driving an oscillating current through the receiver. Both coils will be in parallel with capacitors in order to reduce some losses to parasitic impedance. Additional capacitors may be placed to filter the signals and to snub the inductive kickback on the transistor. The current passing through the receiver will then pass through a full bridge rectifier constructed from a diode bridge in parallel with a capacitor. This unregulated DC voltage (hovering around 7-10 V) will then pass through a 7805 Voltage Regulator to produce the desired 5 V output. Because we can control the switching frequency directly with the Arduino, we aim to experiment with our code in order to improve power delivery.

Objectives

• The objective of this project is to create a working wireless power delivery system as described above. The device should be powered by the Li Ion battery and should be capable of transferring power over the coupled coils from several millimeters distance.
• For the demo, we intend to demonstrate power transfer by lighting an LED with our regulated power on the receiver end. have people with compatible phone models place their phones on the charger. For those with iPhones, will also 3D print a phone case that will house an iPhone wireless adapter. The goal will be for the phones to give an indication that they are in fact charging.

Challenges

In order to accomplish the above stated goals, we must learn:

• The probable challenges may include.
• How to use PSpice/MutliSim or some other circuit simulation software to create a schematic of our design and simulate its behavior under different parameters.
• How to use SolidWorks or equivalent 3D design software to design our iPad case and the body of the charging stand.
• How to configure the internal battery within the charging stand so that it can both be charged by an exterior wall outlet and can provide power to the transmitting coil.
• How to program on Arduino
• How to design and implement control algorithms to improve power delivery for multiple phone orientations.
• How to wind coils of wire to obtain desired specifications.
• About basic manufacturing standards for wireless compatible phones and other components that will be included in our design.

In addition, we will encounter the following safety challenge:

• To ensure user safety, we will need to figure out how to detect temperature of the charging stand with our microcontrollers so that the device can power off it it gets too hot (loose resonant coupling can have higher heat emissions than tight coupling).

Gantt Chart

Budget

• Two wireless charging coils: 2 x $8.22 = $16.44 (Link)
• Battery Management IC: $4.50 (Link)
• 7805 Voltage Regulator: $0.95 (Link)
• Temperature Sensor: $0.69 (Link)
• 7.4 V Lithium Ion Battery: Supplied by Class
• 2 3.7 V Li Ion Batteries: Supplied by Class
• Lithium Ion Battery Charger: Supplied by Class
• Breadboard: Supplied by Class
• Arduino: supplied by class
• 3D-printed parts: supplied by class
• MultiSim Circuit simulation software: supplied by school
• MOSFET Transistor: $6.05 (Link)
• Resistors: $0.10+$0.10+$0.1+$0.56+$1.55= $2.41 (Link 1) (Link 2) (Link 3) (Link 4) (Link 5)
• Spark Fun Capacitor Kit: $6.95 (Link)
• Diodes (for Rectifier Bridge): $5.38 (Link)
• LED's: Supplied by Class

Total before tax and shipping: $43.37;