If the water level in a borewell drops below the threshold level for pumping, its pump motor may get air-locked or even burn out due to dry running. It is inconvenient for farmers to walk all the way to their fields at night just to switch the pump motor ‘off.’ Besides, he may never get to know the problem This problem can be solved by using this GSM-based system that will automatically give the user a call on his mobile phone when the water level in the borewell drops below or rises to the threshold level for pumping. The user can also remotely switch on or switch off the pump motor by sending an SMS from his mobile phone. The system is simple, reliable, portable and affordable.

1. construction
103www.efymag.com Electronics For You | May 2012
GSM-Based Borewell
Water-Level Monitor
Gurunath Reddy farmers to walk all the way to their
fields at night just to switch the pump
motor ‘off.’ Besides, he may never get
to know the problem.
This problem can be solved by
using this GSM-based system that
will automatically give the user a
call on his mobile
phone when the
water level in the
borewell drops
below or rises to
the threshold lev-
el for pumping.
The user can also
remotely switch
on or switch off
the pump motor
by sending an SMS from his mobile
phone. The system is simple, reliable,
portable and affordable.
Circuit description
Fig. 1 shows the block diagram of
the GSM-based borewell water-level
monitoring system. Fig. 2 shows the
complete circuit. It comprises the
power supply section, water-level sen-
sor circuit, microcontroller, MAX232
driver, relay driver and GSM modem.
The GSM board has a valid SIM card
with sufficient recharge amount to
make outgoing calls.
The circuit is powered by regulated
5V DC. The 220V, 50Hz AC mains is
stepped down by transformer X1 to
I
f the water level in a borewell
drops below the threshold level
for pumping, its pump motor may
get air-locked or even burn out due
to dry running. It is inconvenient for
Fig. 1: Block diagram of gsm-based borewell water-level monitoring system
Fig. 2: Circuit of gsm-based borewell water-level monitoring system
sunil kumar
& Sani theo

2. construction
104 May 2012 | Electronics For You www.efymag.com
deliver a secondary output of 12V, 250
mA. The transformer output is recti-
fied by bridge rectifier br1, filtered by
capacitor C1 and regulated by IC 7805
(IC3). Capacitor C2 bypasses ripples
from the regulated supply. LED1 acts
as the power-‘on’ indicator. Resistor R1
limits the current through LED1.
The AT89C51 microcontroller is
connected to the water-level sensor
circuit, relay driver and MAX232. The
microcontroller is programmed to take
necessary actions. The mobile number
used in the GSM modem is included in
the code before burning the code into
the microcontroller.
The water-level sensor circuit
comprises transistor T1 (BC548) as
sensor driver and water sensors A and
B dipped into the borewell along with
the pipe. Sensor A is dipped to the
threshold point for pumping and sen-
sor B is dipped below the pipe to the
bottom of the borewell.
When water in the borewell fills to
the threshold level, it is sensed by sen-
sor A and you get a call on your mobile
phone. Now you can turn the motor
‘on’ by sending the SMS “motor11 on”
from your mobile phone to the SIM
number in the GSM modem. You can
also turn the motor ‘off’ by sending the
SMS “motor11 off”.
Sensor A is connected to the base
of transistor T1 (BC548). When there
is a high voltage at the base, T1 con-
ducts and a low voltage is available
at its collector. This low signal is fed
to pin 12 (port pin p3.2) of the MCU.
Similarly, for a low voltage input at
the base, T1 stops conducting and a
high voltage signal is available at its
collector. So pin 12 of the MCU gets
a high signal input. The high or low
voltage signal at pin 12 is monitored
and processed by the program in the
MCU, and decision to turn the motor
‘off’ taken when the water level dips
below sensor A.
Pin 3 (port pin p1.2) of the MCU
is the output pin. It is connected to
relay-driver transistor T2 (BC548) and
LED2. T2 drives relay RL1, which, in
turn, activates the motor. LED2 glows
to indicate the motor-‘on’ status.
When water level in the borewell
dips below sensor A, the conduct-
ing path between sensors A and B
breaks. Hence a signal is received
by the microcontroller. The micro-
controller turns the running motor
‘off’ and makes a call to the user’s
cell phone through a GSM modem
Fig. 3: GSM modem
Table I
Motor, Mobile and LED Status for Different Water Levels
Borewell Water level Motor Mobile LED2 Remarks
Full Above point A On Call from modem On SMS operation to turn on/off
the motor
Empty Below point A Off Call from modem Off SMS operation not allowed
Table II
Key Features of SIM300 Series
Features Implementation
Power supply Single supply voltage of 3.4V-4.5V
Power saving Typical power consumption in SLEEP mode: 2.5 mA
Frequency bands  SIM300 tri-band (EGSM 900, DCS 1800, PCS 1900). The band can be
set by AT COMMAND, and default band is EGSM 900 and DCS 1800
 Compliant to GSM Phase 2/2+
SMS  MT, MO, CB, text and PDU mode
 SMS storage: SIM card
 Supports transmission of SMS alternatively over CSD or GPRS. User can
choose the preferred mode
SIM interface Supported SIM card: 1.8V, 3V
External antenna Connected via a 50-ohm antenna connector or antenna pad
Two serial interfaces  Serial port 1: Seven lines on the serial port interface
 Serial port 1 can be used for CSD FAX, GPRS and sending AT command
of controlling module
 Serial port 1 can use multiplexing function, but you cannot use serial
port 2 at the same time
 Autobauding supports baud rate of 1200 to 115,200 bps
 Serial port 2: Two lines on serial port interface, /TXD and /RXD
 Serial port 2 used only for transmitting AT command

3. construction
105www.efymag.com Electronics For You | May 2012
to indicate that the water level is too
low to pump the water and the motor
has been switched off. In this way,
the motor is protected from airlocks
and burnouts due to dry running.
The status of motor, water level and
LED2 are shown in Table I. The GSM
modem used in this project is SIM300
V7.03 (refer Fig. 3). Its key features are
listed in Table II.
GSM modem SIM300 V7.03
The GSM module is a specialised type
of modem which accepts a SIM card
and operates on a subscriber’s mobile
number over a network, just like a cel-
lular phone. Basically, it is a cellphone
without display. Modem SIM300 is a
triband GSM/GPRS engine that works
on EGSM 900MHz, DCS 1800MHz and
PCS 1900MHz frequencies.
GSM modem is RS232-logic-level
compatible, i.e., it takes -3V to -15V as
logic ‘high’ and +3V to +15V as logic
‘low’. MAX 232 is used to convert TTL
into RS232 logic level and vice versa.
Hence MAX232 is a voltage-level
converter used between the microcon-
troller and the GSM board.
The signal at pin 11 of the micro-
controller is sent to the GSM modem
through pin 11 of MAX232. This signal
is received at Pin 2 (RX) of the GSM
Parts List
Semiconductors:
IC1 - AT89C51 microcontroller
IC2 - MAX232 driver
IC3 - 7805, 5V regulator
BR1 - 1A bridge rectifier
T1, T2 - BC548 npn transistor
LED1, LED2 - 5mm light-emitting diode
D1 - 1N4007 rectifier diode
Resistors (all ¼-watt, ±5 per cent carbon):
R1 - 1-kilo-ohm
R2, R6 - 470-ohm
R3, R4 - 10-kilo-ohm
R5 - 100-kilo-ohm
Capacitors:
C1 - 1000µF, 25V electrolytic
C2, C4-C7 - 0.1µF ceramic
C3 - 10µF, 16V electrolytic
C8, C9 - 22pF ceramic
Miscellaneous:
X1 - 220V AC primary to 12V,
250mA secondary
transformer
RL1 - 12V, 1C/O relay
S1 - Tactile switch
XTAL
- 11.0592MHz crystal
GSM modem - SIM300 V7.03 modem
- Two water-level steel sensor
rods
Table III
List of Commands
Command Description
AT Check whether the serial interface
and GSM modem are working
ATE0 Turn echo ‘off’ when there is less
traffic on serial line
AT+CNMI Display the new incoming SMS
AT+CPMS Select SMS memory
AT+CMGF SMS string format—how they are
compressed
AT+CMGR Read the new message from a
given memory location
AT+CMGS Send message to a given recipient
AT+CMGD Delete message
modem. The GSM modem transmits
the signal from Pin 3 (TX) to the mi-
crocontroller through MAX232, which
is received at pin 10 of IC1.
Software program
The software program is written in
‘C’ language and compiled using Keil
software. The AT commands listed in
Table III are used in the code to receive
the mobile signal. The hex code of the
program is burnt into the MCU using
Flash Magic software.
Construction and testing
An actual-size, single-side PCB layout
of the GSM-based borewell water-level
monitoring system is shown in Fig. 4
and its component layout in Fig. 5.
Fig. 4: An actual-size, single-side PCB for the GSM-based borewell water-level monitoring system
Fig. 5: Component layout for the PCB

4. construction
106 May 2012 | Electronics For You www.efymag.com
Fig. 6: Author’s prototype
For testing the circuit, proceed
as follows:
1. After assembling all the com-
ponents on the PCB, connect TX and
RX pins of the GSM modem to pins 13
and 14 of MAX232, respectively. Insert
a valid SIM in the card holder of the
GSM modem.
2. Connect ground pin of the GSM
modem to the ground rail of the cir-
cuit.
3. Use two single-strand (hook-up)
wires as sensor A and sensor B. (In the
actual application, use of steel rods as
sensors is recommended.) Hang the
sensors into a bucket or mug such that
sensor A is above sensor B.
4. Pour water into the bucket until
the water level reaches sensor A.
5. Now switch on the circuit.
You should get a call on your mobile
phone. This indicates that you can turn
the motor ‘on.’
6. Send SMS “motor11 on” from
any mobile phone to the SIM in the
modem to turn the motor ‘on’. You
can also turn the motor ‘off’ by send-
ing “motor11 off” message from any
mobile phone.
7. Now remove water from the
bucket until the water level in the
bucket dips below sensor A. The mo-
tor should automatically switch off
and you should receive a call from
the modem simultaneously alerting
you that the borewell (bucket in this
case) is empty and the motor has been
switched off.
After testing the above steps, you
can install the system in the borewell
by inserting sensors A and B into the
pipe with sensor B placed at the bot-
tom of the borewell as shown in the
circuit. Your borewell monitoring sys-
tem is now ready for use. The author’s
prototype is shown in Fig. 6.
EFY note. The source code of this
article is available on www.efymag.
com. 
The author is a student of BE in electronics and
telecommunications at SIT, Tumkur