Wireless Charging System

1 Project Overview
A recent fad in power supply design is to create power supplies that charge devices wirelessly. This means that the power supply is not plugged into the device being charged (though it will be in close proximity, even physical contact). Wireless power transfer technology has been around for a long time; however, recent advances have allowed it to become more practical, and recent interest in the consumer market has brought it to the center of attention. The goal of this project is to create a wireless power transmission system that is capable of transmitting power with 50% efficiency (power absorbed by target device per unit of power radiated by transmitter).

Since most consumers own several different handheld devices, such as cellular phones, pagers, PDAs, or MP3 players, it is expected that the charging system will be compatible with a variety of devices. Versatility is important for developing a marketable, competitive system. Furthermore, the system should be capable of charging multiple devices (whether identical devices or otherwise) simultaneously. To handle this requirement the charger will have several designated areas for devices to be placed on the charging surface. These "hot spots" reduce the freedom to place the devices anywhere on the surface, but eliminate the need for the charger to track the physical location of each device and transmit the correct amounts of power in the proper directions, an extremely complicated problem.

In the interest of efficiency, the handheld device shall be capable of monitoring its own level of charge. It will signal back to the charger base when the battery is full, such that the charging system will cut off power transmission to avoid wasting energy. The data transfer to signal the device ID number and charge status will occur over an SPI connection between microcontrollers mounted on the target device and on the charger base.

The interface should require minimal modification of the device to be charged; considering that the devices are handheld, a bulky modification would be unacceptable. Additionally, the system shall be robust and safe. Safety encompasses interactions with both humans and with other electronic devices that may be present in the environment. It shall fulfill the system requirements over 20 hours of usage during testing.

Minimum Requirements

• Wireless
• Charging multiple devices simultaneously
• Safe
• Robust
• Versatile
• Efficient
• Rapid charging rate
• Low cost
• Monitoring capabilities

Group Members

Tawalin Opastrakoon
Email: opastrat@REMOVEonid.orst.edu

Ben Waters
Email: watersbe@REMOVEonid.orst.edu

Allen Waters
Email: watersal@REMOVEonid.orst.edu

Mentors

Don Heer
Tim Marr

Sponsor
Intel

2 Needs Identification and Background Research
3 System Requirements and Desired Features
4 Design Solutions
5 Top Level Block Design

5.1 Power Supply
5.2 Device Sensing
5.3 Charging Controller
5.4 Charging Controller Code
5.5 Power Transmission Coils
5.6 User Display
5.7 Radiation Monitoring (Removed from design)
5.8 Data Receiver (Removed from design)
5.9 Power Receiver
5.10 Device Power Regulator
5.11 Battery Charge Sensor
5.12 Chassis
5.13 Battery Sensor Controller Code
5.14 Battery Sensor Controller

6 Testing

6.1 Testing Evidence

7 Project Timeline
8 Budget
9 Expo Materials

References