28-06-2012, 11:30 AM
Cellphone-Based device Control with Voice Acknowledgement
Cellphone-Based device Control with.pdf (Size: 1.65 MB / Downloads: 112)
Here is a circuit that lets you
operate your home appliances
like lights and water
pump from your office or any other
remote place. So if you forgot to switch
off the lights or other appliances while
going out, it helps you to turn off the
appliance with your cellphone. Your
cellphone works as the remote control
for your home appliances. You can
control the desired appliance by pressing
the corresponding key. The system
also gives you voice acknowledgement
of the appliance status.
Circuit description
Fig. 1 shows the circuit for cellphonebased
device control with voice acknowledgement.
It comprises microcontroller
AT89C51, DTMF decoder
MT8870, voice recording/playback
device APR9600 and a few discrete
components.
Microcontroller AT89C51 is at the
heart of the circuit. It is a low-power,
high-performance, 8-bit microcontroller
with 4 kB of flash programmable
and erasable read-only memory
(PEROM) used as on-chip program
memory, 128 bytes of RAM used as
internal data memory, 32 individually
programmable input/output (I/O)
lines divided into four 8-bit ports, two
16-bit programmable timers/counters,
a five-vector two-level interrupt architecture,
on-chip oscillator and clock circuitry.
A 11.0592MHz crystal (XTAL1) is
used to provide basic clock frequency
for the microcontroller. Capacitor C3
and resistor R3 form the power-on
reset circuit, while push-to-on switch
S20 is used for manual reset.
Port pins P1.0 through P1.7 of the
microcontroller are configured to get
Parts List
Semiconductors:
IC1 - AT89C51 microcontroller
IC2 - APR9600 voice recording
and playback device
IC3 - MT8870 DTMF receiver
IC4 - ULN2003 relay driver
IC5 - 7806, 6V regulator
D1-D5 - 1N4007 diode
LED1-LED3 - 5mm LED
Resistors (all ¼-watt, ±5% carbon):
R1-R3 - 10-kilo-ohm
R4, R6, R15 - 100-kilo-ohm
R5 - 470-kilo-ohm
R7 - 220-kilo-ohm
R8 - 39-kilo-ohm
R9, R10 - 4.7-kilo-ohm
R11 - 1-kilo-ohm
R12 - 220-kilo ohm
R13, R14, R16 - 470-ohm
RNW1, RNW2 - 10-kilo-ohm resistor
network
Capacitors:
C1, C2 - 33pF ceramic disk
C3 - 10μF, 16V electrolytic
C4, C6-C8,
C11, C15 - 0.1μF ceramic disk
C5 - 4.7μF, 16V electrolytic
C9, C10 - 22μF, 50V electrolytic
C12 - 0.22μF polyster
C13, C14 - 0.47μF polyster
C16 - 1000μF, 35V electrolytic
Miscellaneous:
S1-S16, S20 - Push-to-on switch
S17, S18 - 2-way DIP switch
S19 - SPDT switch
S21 - On/off switch
XTAL1 - 11.0592MHz crystal
XTAL2 - 3.579MHz crystal
RL1-RL6 - 6V, 1C/O relay
MIC1 - Electret mic
LS1 - 1W, 16-ohm speaker
CON1 - Mobile phone headset
connector
voltage greater than threshold of the
steering logic VTSt detected at St causes
the device to register the detected tone
pair. The guard time output resets the
external steering time constant, and its
state is a function of ESt and the volt-
Table I
Functions of Switches and
Mobile Keys
Switches Mobile Function
key
S1 1 Select Device 1; On/Off
S2 2 Select Device 2; On/Off
S3 3 Select Device 3; On/Off
S4 4 Select Device 4; On/Off
S5 5 Select Device 5; On/Off
S6 6 Select Device 6; On/Off
S7 * Initialise to inform the
status of the device
S8 # On/off the voice alert
cONSTRUcTION
76 • June 2010 • electronics for you www. e f y m a g . com
Fig. 1: Circuit for cellphone-based device control with voice acknowledgement
cONSTRUcTION
w w w. e f y m a g . c o m electronics for you • June 2010 • 77
R1, respectively. Here, we are using
two control sources, switches and mobile’s
key. DIP switches S17 and S18
select the control sources as shown in
Table II.
Pin 2.5 of Port P2 is configured to
show the rest status. That is, if none of
the control sources is selected by DIP
switches S17 and S18, LED1 glows.
Resistor R14 limits the current through
LED1.
Voice acknowledgement is provided
by the APR9600 (IC2). It is a
single-chip voice recording and playback
device that can record and play
multiple messages at random or in
sequential mode for 60 seconds. The
user can select sample rates with corresponding-
quality recording lengths.
Microphone amplifier, automatic gain
control (AGC) circuits, internal antialiasing
filter, internal output amplifier
and message management are some of
the features of the APR9600.
Here the APR9600 is configured in
random-access mode, which supports
two, four and eight messages of fixed
durations. The length of each message
is the total recording length available
divided by the total number of memory
segments/tracks enabled.
Audio processor APR9600 can store
up to eight voice messages. Port P0
pins and P2.7 are configured to communicate
with IC2. Port P0 pins
trigger selection of the message.
Port pin P2.7 is the input signal to
identify whether the voice message
is playing or not.
Pins P3.0 through P3.5 of Port
P3 control the devices with the
help of relays RL1 through RL6 via
relay driver IC4.
A speaker is connected to IC2
for audio output. The speaker
output drives the mic input of the
mobile for audio acknowledgement.
An electret microphone
MIC1 is connected to IC2 to record
the voice in IC2. LED2 flashes to
show the busy status of IC2 during
recording and playback. The
audio messages to be recorded in
APR9600, by using trigger switches
S9 through S16, are shown in
Table III. SPST switch S19 is closed
for recording and switch S19 is
opened for playback.
Fig. 3 shows the power sup-
Table II
Control Source Selection
Using DIP Switches
S17 S18 Control status
0 0 R est status
0 1 Switches only
1 0 Mobile only
1 1 Switches and mobile
Fig. 3: Power supply circuit
Fig. 2: Pin configuration of mobile headset
Fig. 4: A single-side, actual-size PCB layout for cellphone-based device control with voice
acknowledgement
age at St.
Port P3 pins P3.6 and P3.7 of IC1
are configured to select the control
source for the devices. These are connected
to DIP switches S17 and S18
and pulled high via resistors R2 and
cONSTRUcTION
78 • June 2010 • electronics for you www. e f y m a g . com
Table III
Voice Recording Chart
Switch Trigger of IC Voice
S9 1 Name of Device 1
S10 2 Name of Device 2
S11 3 Name of Device 3
S12 4 Name of Device 4
S13 5 Name of Device 5
S14 6 Name of Device 6
S15 7 “Status On”
S16 8 “Status Off”
Table IV
DTMF Value of Mobile Keys
Key StD Q3 Q2 Q1 Q0
1 H 0 0 0 1
2 H 0 0 1 0
3 H 0 0 1 1
4 H 0 1 0 0
5 H 0 1 0 1
6 H 0 1 1 0
* H 1 0 1 1
# H 1 1 0 0
ply circuit. The 230V AC mains is
stepped down by transformer X1 to
deliver the secondary output of 9V,
500 mA. The transformer output is
rectified by a full-wave bridge rectifier
comprising diodes D1 through
D4, filtered by capacitor C16 and then
regulated by IC 7806 (IC5). Capacitor
C15 bypasses the ripples present
in the regulated 6V power supply.
LED3 acts as a power-on indicator
and resistor R16 limits the current
through LED3.
An actual-size, single-side PCB
for cellphone-based device control
with voice acknowledgement is
shown in Fig. 4 and its component
layout in Fig. 5.