Transcript EE 682x autumn 2002 Power Monitor and Data Logging System

EE 682x autumn 2002
Power Monitor and Data
Logging System
The Original RFP for EE 582
•Students in EE 582 are requested to submit a proposal
for the design and development of a power monitor and
data logging system. The system would include a device
that a residential user could plug into any 120-volt wall
outlet and then plug an appliance, etc. into it. This
device would measure "power things" and display a
selectable quantity, e.g., volts, amps, watts, etc. In
addition, a communication system is to be designed to
transmit the information to a PC, within the house, for
data logging purposes and some appropriate software
developed to manipulate, display and store the data.
•General specifications include that the device be
inexpensive, safe, portable, self-powered, i.e., powered
from the 120-volt wall outlet, capable of carrying 15
amps rms continuously, and be small enough so as not
to be obtrusive when used within a home. The
communication system can be either wireless
(preferred) or can use some type of hard wire system.
To be practical for the ordinary user to implement, the
communication system should not require any
significant alteration or addition to normal homes. It
can be assumed that a personal computer would be
available, either a PC or a Macintosh.
•The overall system incorporates technology from many
of the academic areas within the Department of Electrical
Engineering:
 Electronics -- measure/"massage" the voltage and current waveforms so as to
apply to a "microprocessor" and display; A/D converters,
 Digital -- "manipulate" via a microprocessor the data to determine "power
things," such as P, power factor, etc.,
 Power -- know how to determine the various "power things" desired from
sampled instantaneous voltage and current waveforms,
 Communications -- send the information (hopefully wireless) to the PC; also
need a "receiver" in the PC,
 Control -- consider if one had "smart" switches or controls on appliances, then
these devices could be "controlled,"
 Electromagnetics – included as part of the sensors and communications,
 Solid-state – included as part of the sensors and communications.
120 VAC, 1phase, 3 wire
black
white
green
120 VAC
1phase
3 wire
Iline
black
Vline
white
Voltage
transforme
r
Curren
t
Transf.
green
Iline
aCT
Vline
aVT
Attenuation
circuitry
PC
Attenuation
circuitry
Receiver
A/D
LCD display
MCU
Transmitter
Measurement/calculation of “power variables”
•A/D converter: sample v(t) and i(t)
•Determine rms value of each
•Determine phase shift and then power (watts)
v(t)
i(t)
phase
shift
Data sheet list:
o
Voltage transformer -
o
Current transformer –
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A/D --
o
MCU –
o
LCD –
o
Transmitter –
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Encoder --
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Receiver –
o
Decoder – same chip as the encoder
o
RS232 driver –
o
+5 V supply – maybe regulator and/or bread board supply
o
antenna -