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Document Sample
Group #24
Guercy Metayer
Louis Chrispin
Jacques House
Larry Lowe
Energy Monitoring System
• Measures the power consumption of the house
or individual appliances
• Detect faulty appliances and where most power
is being consumed
• Display power in kW/h, the cost in $ and cents
• Send the data to a computer database and
predict cost of next electric bill.
Motivation
• Learn how power company measures our
power consumption for the electric bill
• See how we can help with the energy
crisis in the residential sector
• We wanted to see if the utility company
was charging customer correctly
• We all wanted to do a project that has to
do with power
The Problem
• No standardized way for consumers to estimate
electrical energy usage.
• Americans may spend around 4.7 percent of their
take-home pay on utility bills. Low income residents,
conversely, will spend an average of 19.5 percent of
their annual income on utility bills.
• Average household receiving social security or
family aid spends 19-25% of income on utilities.
Source: National Low Income Energy Consortium
Specification & Requirements
• Specs. • Req.
– Measures the power – Operating Temperature: -5°
consumption of the house to 655°C
or individual appliances – Accuracy within +5
– Display power in kW/h, the – Line voltage = 125 V (rms)
load, cost, and power – Class 100 meter with IMAX
– Send the data to a = 100 A
computer database – Meter constant = 3200
– Graphical Interface – imp/kWh
Windows Compatible – CT Turns ratio = 300:1
– Meter calibrated at IREF =
10 A
– Power dissipation at Ib =
125 V X 10 A = 1.25 kW
– V1 = 23 mVrms max
Block Diagram
RMS to DC Converter
Current Transformers OPAMP 741
Analog to Digital converter
Analog Multiplier
Multiplexer 16
EEPROM Microcontroller
Reference Voltage
Potential Transformer
Positive Voltage Positive Voltage
Regulator Regulator
Negative Voltage
Regulator Dual Line Driver
Topics Covered
• Overall design layout
• Microcontroller
• EEPROM
• Voltage/Current measurement
• Communication
• Display to a Computer
• Future Work
• Budgeting and scheduling
Approaches Considered
• Image Recording • Panel Connected
Device (suggested by Device
Prof Weeks) – Wall mounted box
– An image recorder measure power from a
with sensors to detect panel
the six sides of a – The box sends the
digital number data to a remote
– The image recorder display
would in turn transmit – The box also sends
the data to a remote data to PC for monthly
display monitoring
Energy Measurement Overview
• Show the different types of sensor
methods there are, and why we choose
the type of method for this design.
• Describe how the system knows which
load to pick.
• Looking at the following table, one can see
the strengths and weakness of the
different energy measuring technologies
there are.
Current measurement
Comparison Table
Energy Measurement
• Current Measurement
– Current Transformers (CT)
– CT placed around each load.
Current Transformer General
Specifications
• Ranges: 0A to 20A
• Outputs: 0-23mV. Instantaneous
outputs are voltage only.
• Core type: Solid core, based on
dc Hall sensing
• Voltage Range: 0 to 300 volts
maximum.
• Accuracy: ±1.0% for 0-15A, 2.0%
for 15-20A
• Working temperature range:
Typically -20°C - 50°C. Functional
temp range > –20°C - 70°C
• Frequency response: DC- 50-
400 Hz max
• Mounting: Current transformers
can be mounted externally via an
external cable or bracket, fixing
points provided.
Equations
• To get the meter error we
calculated the measured power
versus the calculated power.
• Phase error is calculated
• The power from the line
• The Burden Resistor is
calculated
RBurden = Vo / Is
Multiplexer Applications
• For our project the microprocessor selects
each CT, one at a time, for measurement.
• The switching is achieved with a solid
state multiplexer (MUX-16).
• When a particular CT is selected, the
microprocessor waits ten seconds for the
circuitry to settle and then takes a reading.
Multiplexer
• The MUX-16
connects a single
output to one of the
16 analog inputs
depending on the
state of a 4-bit binary
address.
Multiplexer Features
• JFET switches rather
than CMOS.
• Low leakage current.
• Digital inputs compatible
with CMOS and TTL.
• Temperature ranging
from -55 to 125 degrees
C.
• Over-voltage protection
Equations
• F = (I0*S0*S1*S2*S3) +
(I1*S0*S1*S2*S3) +
(I2*S0*S1*S2*S3) +
(I3*S0*S1*S2*S3) +…+
(I16*S0*S1*S2*S3)
Computation and reading the input
from the Ct and Vt transducer
• A taking the signal from the MUX
16
• 741 Was used to amplify the
signal so that it can used an input
for AD536AJD and AD633JN
• The 741 is good at compensated
(its frequency response is tailored)
to ensure that under most
circumstances it won't produce
unwanted false oscillations
Computation and reading the input
from the Ct and Vt transducer
• The AD536AJD computes the true
RMS level of a complex ac input
signal and gives an equivalent dc
output level.
• The AD536AJD will work well
supply voltage levels from 5 to 36
volts.
• The AD536AJD is very efficient in
converting the rms signal to a dc
level. There is only a .5% error
while the conversion is taking
place.
Computation and reading the input
from the Ct and Vt transducer
• The AD536A is laser trimmed to minimize input and output offset voltage, to
optimize positive and negative waveform symmetry (dc reversal error), and
for full-scale accuracy at 7 V rms. As a result in this project, no external
trims are required to achieve the rated unit accuracy
• The input and output pins are fully protected. The input circuitry can take
overload voltages well beyond the supply levels. Loss of supply voltage with
the input connected to external circuitry does not cause the device to fail.
The output is short-circuit protected.
• The actual computation performed by the AD536A follows the equation
• Looking at the AD536AJD circuit it’s subdivided into four major sections:
absolute value circuit (active rectifier), squarer/divider, current mirror, and
buffer amplifier.
Computation and reading the input
from the Ct and Vt transducer
Current Mirror
Absolute Value;
Voltage-current
Converter
One-Quadrant Buffer
Squarer Divider
Computation and reading the input
from the Ct and Vt transducer
• The input voltage (VIN), which can be ac or dc,
is converted to a unipolar current (I1), by the
active rectifier (A1, A2). I1 drives one input of the
squarer/divider, which has the transfer function
• 4I =I^ /I3
2
• The current mirror returns a current I3, which
equals Avg. I4, back to the squarer/divider to
complete the implicit rms computation.
Computation and reading the input
from the Ct and Vt transducer
• The current mirror also produces the
output current, I = 2I . I can be used
OUT 4 OUT
directly or converted to a voltage with R 2
and buffered by A4 to provide a low
impedance voltage output
• . The transfer function of the AD536A
results in the following:
Computation and reading the input
from the Ct and Vt transducer
• The AD633 is a complete four-
quadrant multiplier
• Applications: Multiplication,
Division, Squaring
Modulation/Demodulation,
Phase Detection Voltage
Controlled
Amplifiers/Attenuators/Filters
• The AD633 is laser calibrated
to a guaranteed total accuracy
of 2% of full scale.
Computation and reading the input
from the Ct and Vt transducer
• -The ADC0831CCN is an analog to
digital converter. It converts
continuous signals to discrete digital
numbers.
• The ADC0831 series are 8-bit
successive approximation A/D
converters with a serial I/O and
configurable input multiplexers with up
to 8 channels. The serial I/O is
configured to comply with the NSC
MICROWIRE™ serial data exchange
standard for easy interface to the
COPS™ family of processors, and can
interface with standard shift registers
or µPs.
• The microprocessor performs an
analog-to-digital conversion which
yields a binary number ranging from 0
to 255.
MCU Requirement
• Must be easy to use
• Multiple I/O lines
Microcontrollers
MCU Advantages Disadvantages
Clock speed: 54 MHz Chip cost: $18.70
Rabbit3000 Op. Volt.: 1.8-3.6 V Board cost: $239
56 I/O pins No free samples
Chip cost: $3.81 Clock speed: 16 MHz
ATmega16 Board cost: $79 Op. Volt.: 2.7-5.5 V
Free samples Advanced
Only 33 instructions Op. Volt.: 2.5-6.25 V
PIC16C56 Clock speed: 20 MHz One time programmable
Chip cost: $3.03
Chosen MCU
PIC16C56 features:
• 33 instructions
• 20 MHz speed
• 2.5 to 6.5 operating voltage
• 18 pin chip & 12 I/O lines
• 1 kB ROM, 25 B of RAM
• 8-bit real time clock/counter
(TMR0) with 8-bit
• Programmable pre-scaler
• Power-on Reset (POR)
• Device Reset Timer (DRT)
• Watchdog Timer (WDT) with its
own on-chip
• RC oscillator for reliable operation
• Programmable Code Protection
• Power saving SLEEP mode
Pin Layout
Programming
• Assembly • C Language
– Advantages – Advantages
• Smaller Code Size • Portability of code
• Efficient • Familiarity Among
– Disadvantages Group
• Overhead – Disadvantages
• Unfamiliarity Among • Longer code size
Group • Compiler doesn’t catch
all errors
Architecture
Example Code
Changing the Prescaler:
• CLRWDT ;clear watchdog timer
• CLRF TMRO ;clear prescaler
• MOVLW B'00xx1111'
• OPTION
• CLRWDT ;PS<2:0> are 000 or 001
• MOVLW B'00xx1xxx‘ ;setting the prescaler
• OPTION
Development Board
PICSTART Plus Features:
• Programs PIC
microcontrollers,
including program
memory, configuration
bits and ID locations
• Works as an application
on a PC host system
within the MPLAB
Integrated Development
Environment (IDE)
• Communicates with the
PC via a standard RS-
232 cable
PCB
• PCBExpress.com • Ourselves
– Advantages – Advantage
• Professional • Cheaper
– Disadvantage • Fix errors
• 2 Lots of a 9 in2 board is – Disadvantage
$60 • Raw finish
• Risky
Storage: EEPROM
Reason:
• Not enough internal memory on the
microcontroller.
• It can be erased and it is more durable
than Flash
Storage: EEPROM
93LC56 features:
• Sequential read
function
• 1,000,000 E/W cycles
ensured
• 256 Bytes
• Data retention: over
200 years
• Temperature Range:
-40°C to +85°C
Power Supply
• Main Power Supply
Power Requirements
Component Current (mA) Voltage (V) Power(mW)
CT Transducer 0 0 0
VT Transducer 0 0 0
MUX16 .2 15 3
Pic16c56-x 1 3 3
AMP 741 1.7 15 25.5
AD536AJD 1.2 12 14.4
AD633JN 1.4 15 21
ADC0831CCN 1 3 3
93LC56 EEPROM 1 3 3
7150 RS-232 1.2 7 8.4
Total 8.7 81.3
CPU Capture
Capture GUI
open com port
while not CRLF
listen
//discard first input
wend
for i=1 to i=16
//4 values from microcontroller
read j,k,l,m
//index values by channel #
A[j] = k
B[j] = l
C[j] = m
end-for
close com port
CPU Display
Display GUI
//double letter arrays signify past readings
(BB, AA)
i=0;while(i<16){
//subtract past readings
B[i] = B[i] - BB[i];
A[i] = A[i] - AA[i];
F[i] = B[i] + A[i] * 65536;
// CT = current transformer size
// LV = line voltage
// PF = power factor
// SCAL, SCA2, PRICE
//Scale to amps
A[i] = A[i]/SCAL*CT[i]/20;
//Scale to kw
K[i] = A[i] *LV[i]*PF[i]/1000;
//Scale to kwh
G[i] = (F[i]/SCA2*CT[i]/20*PF[i]*LV[i]/120);
//Calculate cost
C[i] = PRICE * G[i] / 100; i++;}
HTML Output
Obstacles
Hardware Design
• Numerous design changes
• Wasted resources
• Features removed:
– Wireless CPU serial connection
– Wireless LCD room modules
• Temperature sensor
• Humidity sensor
– Network connectivity
– Meter-mounted LCD display
Presentation Computer
Display
• UCF computers
– administrative rights
– MSCOMM32.OCX error
• Personal laptop
– Windows Vista (missing MSCOMM32.OCX)
– USB Ports (serial-to-USB not working)
• Old desktop computer
– Windows XP
– Serial port
– Descent test load
– Heavy to carry around
Model House
• Plastic doll house
– Cheaper and less initial work
– Hard to cut/modify plastic
– It’s a doll house
• Custom wooden house
– More expensive
– Easy to modify and wire rooms
– Looks more professional
Timeline
Energy Monitoring
Jan 2007 Feb 2007 Mar 2007 Apr 2007
ID 01/06/2007 04/27/2007 Duration
Senior Design II 7/1 14/1 21/1 28/1 4/2 11/2 18/2 25/2 4/3 11/3 18/3 25/3 1/4 8/4 15/4
1 Research 1/25/2007 3/8/2007 31d
2 Ordering Parts 1/8/2007 2/1/2007 19d
3 Design Modeling 2/5/2007 3/1/2007 19d
4 Assembly 2/27/2007 4/9/2007 30d
5 Testing Phase 4/4/2007 4/25/2007 16d
6 Troubleshooting 4/4/2007 4/18/2007 11d
7 Final Report 4/19/2007 4/24/2007 4d
8 Demonstration of Design 4/26/2007 4/26/2007 1d
Budget
Product Price
Current Transformers(3) $ 81.00
Potential Transformer $ 35.00
AD536AJD: RMS to DC Converter Sample
AD633JN: Analog Multiplier Sample
16-channel Multiplexer Sample
ADC0831CCN: Analog to Digital Converter Sample
93LC56: Serial EEPROM Sample
PIC16C56: Microcontroller $3.05
Development Board $199.1
2N3906: PNP Transistor Sample
LM7805: Positive voltage regulator Sample
LM7912: Negative voltage regulator Sample
LM7812: Positive voltage regulator Sample
SN75150: Dual line driver $ 2.00
LM741: Operational Amplifier Sample
Bread Board $ 15.00
LCD $ 27.00
Miscellaneous (Resistors, Capacitors, Diodes, etc.) $ 75.00
Work Distribution
Louis Jacques Larry Guercy
RMS to DC
Converter Current Transformer Voltage Regulators MCU
Analog Multiplier Multiplexer Dual Line Driver Programming
Analog to Digital
Converter GUI EEPROM
Computer
Electrical Engineer Electrical Engineer Electrical Engineer Engineer
Questions?
