20-10-2012, 01:46 PM
LOW COST ENERGY METER
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ABSTRACT
The energy meter is an electrical measuring device, which is used
to record Electrical Energy .Consumed over a specified period of time in terms of
units.
Every house, small factory, business establishment, shops, offices etc. need at least
one energy meter to register power consumption. The supplier of electrical raises the
bill on the basis reading shown by this meter. The producer of electricity sale the
electricity to the electricity boards and boards has to sale this energy to the consumer.
Consumer needs to pay the amount against the bill raised by the supplier. The data
generate by the energy meter is the base to raise the bill by power supplier. Because
of massive rural and urban electrification programme of Government, there is a good
demand for this product. This product is available in single phase and three phases at
different current rating as per customer's requirement. Here we are introducing a low
cost energy meter using ADE7757.
In our project IC ADE7757 is heart of energy meter. It directly
interfaces with the shunt resistor and operates off the AC input. The only analogue
circuitry used in IC ADE7757 is in the sigma delta ADC’s and reference circuit. All
other signal processing is carried out in digital domain.
The power supply for IC ADE7757 is derived directly from
mains using the capacitor divider network comprisingC13 and C14. Most of the
voltage is dropped across C13 (0.47μF polyester capacitor rated for 630V), while
resistor R13 (470-ohm, 1W) is used as a current limiter. The output acrossC14 is
limited to 15V DC, which serves as an input to regulator 7805(IC2). The regulated 5V
is fed to IC1at its VDD.
METERING IC –ADE 7757
IC ADE7757 (IC1) is at the heart of the energy meter. It directly interfaces with the
shunt resistor and operates off the AC input. The only analogue circuitry used in IC
ADE7757 is in the sigma delta ADCs and reference circuit. All the other signal
processing is carried out in digital domain. The power supply for IC ADE 7757 is
derived directly from mains using the capacitor divider network comprising C13 and
C14. Most of the voltage is dropped across C13 (0.47μF polyester capacitor rated for
630V), while resistor R13 (470-ohm, 1W) is used as a current limiter. C14 is limited
to 15V DC, which serves as an input to regulator 7805 (IC2). The regulated 5V is fed
to IC1 at its VDD.
It is available in 16-lead SOIC narrow-body package. In our PCB layout, it is to be
soldered on the conductor side of the PCB. The IC has an on-chip oscillator, so it
requires no external crystal or resonator, thus reducing the overall cost of building a
watt-hour meter. It operates off a 5V power supply. In operation, the chip directly
interfaces with a shunt resistor (used as the current sensor) and AC analogue voltage
sensing input. It has two analogue input
channels designated as V1 and V2, respectively.
REGULATOR IC-7085
A linear regulator is a voltage regulator based on an active device (such as
a bipolar junction transistor, field effect transistor or vacuum tube) operating in its
"linear region" (in contrast, a switching regulator is based on a transistor forced to act
as an on/off switch) or passive devices like zener diodes operated in their breakdown
region. The regulating device is made to act like a variable resistor, continuously
adjusting a voltage divider network to maintain a constant output voltage. It is very
inefficient compared to a switched-mode power supply, since it sheds the difference
voltage by dissipating heat.
The KA78XX/KA78XXA series of three-terminal positive regulator are
available in the TO-220/D-PAK package and with several fixed output voltages,
making them useful in a wide range of applications. Each type employs
internalcurrent limiting, thermal shut down and safe operating area protection, making
it essentially indestructible.