The document summarizes a solar kiosk project team and discusses current sensing techniques. It describes applications of current sensing, pros and cons of shunt resistors and Hall effect sensors, and how to handle sensed data. The team members and their roles are listed, followed by an explanation of current sensing applications, shunt resistors, the Hall effect, and serial data interfaces. Andre-Marie Ampere's contributions to electromagnetism are also briefly mentioned.

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
VH
L
W
t
+
I
B
EHp
EHn
 
B
v
F 

 E
q
E
q

F
electrons
for
holes
for
q
q
q




+ +
+

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
• I2C 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
– I2C
• Developed by Philips
• 128 Devices on one bus
– USB
• Driver implementation