1. Team 2 Solar Kiosk Project Sponsored by: Team Members: Jakub Mazur - Manager Eric Tarkleson – Presentation/Lab Josh Wong - Webmaster Ben Kershner – Document Preparation

2. Current Sensing Applications Pros Cons The Hall Effect Shunt Resistors Making your Data useful Questions

3. Applications Measuring Power Consumption Design for Safety – GFCIs, fuses, circuit breakers Temperature optimization – High current = hotter components

4. Shunt Resistor Low failure probability Cheap Wastes power Limited sensing range Requires additional voltage measurements Hall Effect Sensor Isolated from current source Higher precision More expensive Can be integrated into an IC device

5. Who is this Guy? André-Marie Ampère (1775 –1836) By1800 scientists where wondering if electricity and magnetism where related. Ampere was one of the first to develop a technique for measuring electricity… essentially a compass with wire wrapped around it. Electrodynamics  Electromagnetics, where studied at this time by: Faraday, Weber Thomson and Maxwell.

6. Shunt Resistor V = IR

7. The Hall Effect When there is a Magnetic field in the presence of a conductor a voltage is induced due to electron and hole drift Electron – negative charge carrier Hole – positive charge carrier

8. Hall Effect VHVH L W t + I B E Hp E Hn + + +

9. The Hall Effect - Math Vhall = -(I*B)/(d*n*e) Rhall = -1/(n*e) current through wire Bfield = Uo*Ip/(2*pi*r) I= current B = Mag Flux Dens d = depth of plate e = electric charge j = current density n = charge carrier dens r = distance to center of wire Uo = 4*pi*10^-7

10. So what? We can use this to our advantage We can detect – B field – Current – Voltage – Charge drift velocity We can do this without having inline components (like a shunt resistor)

11. How do I handle this data? Many types of signals – Reference voltage (LEM sensors) – Voltage drop (Shunt resistor) – Parallel bus (Some ADCs) – Serial interface (Some ADCs, other ICs) Traditional Serial Interface I 2 C Bus

12. How do I handle this data? Sampling by digital ICs – Direct – Indirect Intermediate ADC Direct – Built-in ADC on the PIC Inaccuracies – Parallel High Pin Count

13. Serial Buses Traditional UART/USART Serial – Typically one-to-one communication – Parity checking Serial Protocols – I 2 C Developed by Philips 128 Devices on one bus – USB Driver implementation