Energy and Power Engineering, 2010, 2, 127-130
doi:10.4236/epe.2010.22018 Published Online May 2010 (http://www. SciRP.org/journal/epe)
127
Design of Multi-User Electric Power Management Device
Weiqing Tao, Jing Wang
School of Electric Engineering and Automation, Hefei University of Technology, Hefei, China
Received December 28, 2009; revised February 2, 2010; accepted April 12, 2010
Abstract
The current consumption method of Electric Power Industry is “electricity consumption first, paying for it
later”. The trend of consumption method is Pre-order Electricity. If we adopt the Pre-order Electricity Sys-
tem, we need to replace Traditional Energy Meter with Prepayment Energy Meter. But this alteration is
costly. And the alarm action of Prepayment Energy Meter are bells and alarm lamp, users can not receive
alarm information timely. In this paper, we present the design of Multi-user Electric Power Management
Device. The device uses TMS320F2812 as CPU, with peripheral devices such as mobile phone communica-
tion module MC55, so the device supports remote operation and sends alarm information via SMS, it also
can communicate with the master station by GPRS. The device can be seamlessly integrated into the existing
power system in order to read meter, achieve billing and Pre-order Electricity functions. In addition, the de-
vice has the Harmonic Measurement function, so it is a high cost-effective application.
Keywords: Electric Power Management, TMS320F2812, MC55, SMS, GPRS
1. Introduction
The current consumption method of Electric Power
Industry is “electricity consumption first, paying for it
later”. The trend of consumption method is Pre-order
Electricity. If we adopt the Pre-order Electricity Sys-
tem, we need to replace Traditional Energy Meter with
Prepayment Energy Meter. But this alteration is costly.
Most Prepayment Energy Meter use IC card as
voucher card. Once the IC card does not work properly,
it will affect the normal operation of the Pre-order
Electricity System. The most alarm action of IC card
Prepayment Energy Meter are bells and alarm lamp,
users can not receive alarm information timely.
In this paper, we present the design of Multi-user
Electric Power Management Device. The device uses
TMS320F2812 as CPU, with peripheral devices such
as mobile phone communication module MC55, built-
in a variety of electricity charge calculation method.
The device can collect Energy Meters’ electric energy
information via RS485 Communication Interface or
Pulse Collection Interface, and then do electricity
charge calculation, choose alarm operation or power
on/off operation according to the balance, and there is
a SMS notification after every operation, so users can
receive alarm and operating information timely. If the
master station needs to do a lot of data communication,
the device also can communicate with the master sta-
tion by GPRS. The device can collect many Energy
Meters’ electric energy information via RS485 Com-
munication Interface, to achieve Multi-user Electric
Power Management purposes. We just install the de-
vice in commercial application, and avoid replacing the
existing meter. In addition, the device has the Har-
monic Measurement function, so it is a high cost-ef-
fective application.
2. Design of Multi-User Electric Power
Management Device
2.1. Device Hardware Design
The device uses TMS320F2812 as CPU, with periph-
eral devices such as LCD Module, Key Module, Mo-
bile Phone Communication Module, RS485 Commu-
nication Interface, Pulse Collection Interface, Data
Storage Module, Clock Chip, Power on/off Execution
Module, Signal Conditioning Module and Power Sup-
ply Module. The hardware block diagram of the device
is shown in Figure 1.
TMS320F2812, a member of the TMS320C2000 DSP
generation, is a 32-bit DSP of 150MHz maximum fre-
quency. It has many General-Purpose Input/Output ports
(GPIOA-GPIOF), 2 UART ports (UART1, UART2),
with on-chip A/D sampling function. TMS320F2812

W. Q. TAO ET AL. 128
Figure 1. Hardware block diagram.
is highly integrated, high-performance solutions for de-
manding control applications [1].
LCD Module adopted 128*64 dot matrix LCD dis-
play, controlled by TMS320F2812’s GPIOA. Because
the processing speed of LCD is much slower than
TMS320F2812, control signal is through the latch to
control LCD. LCD refreshes every minute, displays the
current power consumption and the current balance of
user. It also can query information with the operation
of the keys.
Key Module is connected to TMS320F2812’s data
bus, software control TMS320F2812 to scan data bus
every 10 milliseconds. When a button is depressed,
TMS320F2812 do corresponding processing according
to data bus level changes.
Mobile Phone Communication Module adopted
MC55 of SIEMENS, which is connected to TMS320
F2812’s UART2. Administrator and user make SMS or
GPRS remote operation to the device via the Mobile
Phone Communication Module [3]. When the balance
is insufficient, TMS320F2812 controls the module to
use SMS to notify the user timely payment.
The device has two meter reading ports, RS485
Communication Interface and Pulse Collection Interface.
RS485 Communication Interface connects to TMS320
F2812’s UART1 via signal converter and optocoupler.
UART1 sends a signal through the optocoupler and then
through the signal converter to reach RS485 Commu-
nication Interface, RS485 Communication Interface
receives a signal through the signal converter and then
through the optocoupler to reach UART1. Pulse Col-
lection Interface connects to TMS320F2812’s GPIOE
via optocoupler. When the pulse signal reaches GPIOE
via optocoupler, TMS320F2812 gain electric energy
information.
We use an EEPROM chip as Data Storage Module,
Data Storage Module and Clock Chip is connected to
TMS320F2812 via I2C Bus. Since TMS320F2812 has
no hardware I2C Bus, using GPIOB simulate the I2C
Bus Timing controlled by software. Data Storage
Module stored device parameters information, user
information and electricity consumption records. Clock
Chip provides the device with time reference for time-
billing. TMS320
F2812 Power on/off Execution Module is connected to
TMS320F2812’s GPIOF. The module is composed of
optocoupler, relay and breaker. The controlling signals
go through an optocoupler safety quarantined, and then
go through the relay reach breaker, at last breaker re-
sponses the control signal.
Signal Conditioning Module is composed of CT and
PT. The regulated signal followed by the filter circuit,
voltage divider circuit. At last input TMS320F2812’s
on-chip A/D as differential mode to achieve Harmonic
Measurement function.
Power Supply Module is composed of working
power and backup power. Working power is obtained
directly from the feeder and do battery charging at
same time. Backup power is composed of battery.
2.2. Device SMS Function
The device can do Buy Operation, Inquire Operation,
Power On/Off Operation, and Change Parameters Op-
eration by SMS communication. It also can Send
Alarm SMS on its own initiative.
Buy Operation means that administrator add user’s
balance by sending encrypted SMS. Inquire Operation
means that administrator or user inquire balance by
sending SMS. Power On/Off Operation means that
administrator can make power on/off operation by send-
ing encrypted SMS. Change Parameters Operation
means that administrator can change electricity charge
parameters by sending encrypted SMS [5]. Send Alarm
SMS means that the device can send alarm SMS on its
own initiative when the balance is less than some value.
The device stored some cell phone numbers. These
numbers are divided into administrator number and
user number. The device handles the messages as this
flow: first Phone Number Analysis, then Operation
Type Analysis, at last Response Operation. Received
SMS processing flow is shown in Figure 2.
Phone Number Analysis means that, to judge the
sender's number is administrator number or user num-
ber by comparing the sender's number with the num-
bers stored in the device. If the sender's number is not
in the stored number list, delete this SMS, the device
take no action.
Operation Type Analysis means that, the device gets

W. Q. TAO ET AL.129
Figure 2. Received SMS processing flow.
operation information by analyzing SMS, and deter-
mines whether the operation is allowable. Administra-
tor can do Buy Operation, Inquire Operation, Power
On/Off Operation, and Change Parameters Operation.
User can do Inquire Operation. If the SMS senders
want to do limited operation, the device will return an
authority error message to them.
Response Operation means that, the device makes
different operations according to the type of operation.
All operations have SMS receipt to inform the operator
if the operation is successful or not.
In addition, the device send alarm SMS to adminis-
trator number and user number, when the balance is
less than some value.
2.3. Device GPRS Function
The device also has GPRS communication function.
Since the bytes of a SMS is limited, if we need to do a
lot of data communication, using multiple SMS to
communication is costly. For example, query operation
history, query harmonic measurement records, in this
case, the device communicates with the master station
by GPRS.
3. Possible Commercial Applications
In this Pre-order Electricity System, PC master station
controls a mobile phone communication module as an
administrator with the Host Computer Software. Users
carry mobile phones as a user number.
The device collects multiple Energy Meter’s infor-
mation via RS485 Bus. It can manage and control mul-
tiple meter users. In commercial applications, we do
not need to replace the existing meter by Prepayment
Energy Meter, just installing the Pre-order Electricity
device on the basis of the existing system. The
Figure 3. Application of multi-user electric power manage-
ment device.
device used to collect Energy Meter’s information,
calculate electricity and achieve Pre-order Electricity
functions. The possible application of Pre-order Elec-
tricity device is shown in Figure 3.
If the Energy Meter does not have RS485 Commu-
nication function, the device can collect electric energy
information by Pulse Collection Interface. This situa-
tion the device can only manage one Energy Meter.
4. Conclusions
In this paper, we present a design of a Multi-user
Electric Power Management Device. We use high-inte-
grated and high-performance DSP TMS320F2812 as
CPU, with peripheral devices such as mobile phone
communication module MC55. The device can deal
with complicated control information. It has three fea-
tures:
1) Two kinds of electric energy information collect
mode, it can manage and control multiple meter users.
2) Automatic calculation electricity charge based on
different user information and electric energy informa-
tion.
3) With the ability of remote operation via SMS and
GPRS, and sending alarm information via SMS.
The device can be seamlessly integrated into the ex-
isting power system in order to read meter, achieve
billing and Pre-order Electricity functions, can manage
and control multiple meter users. In addition, the de-
vice has the Harmonic Measurement function. The
application of the device can reduce the cost of the
system reform, and it has been successfully used in
Wuhu city of Anhui Province in China.
5
. References
[1] Texas Instruments Incorporated, TMS320F281x Data
Sheet, 2005.
[2] Texas Instruments Incorporated, TMS320F28x Optimiz-
ing C／C ++ Compiler User’s Guide, 2005.
SMS GPRS
RS485 BUS

W. Q. TAO ET AL. 130
[3] SIEMENS Mobile, SIEMENS. MC55/56 Hardware In-
terface Description, 2006.
[4] SIEMENS Mobile, SIEMENS. MC55/56 AT Command
Set, 2003.
[5] J. F. Wang, W. Q. Tao and L. L. Wang, “Design of Mod-
ify the Parameters of LTU by Using SMS,” Microcon-
trollers & Embedded Systems, Vol. 6, 2009, pp. 40-42.
[6] Jiangsu Electric Power Company, Power Marketing
Knowledge Q & A (Part of the electricity tariff), China
Electric Power Press, Beijing, 2004.
[7] Z. B. Jiang, “Power Management/Technical Expertise for
the Use of Electricity,” China Electric Power Press, Bei-
jing, 2002.