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Programmable Home Security Alarm System. Part 1. Schematic


In this project we design low cost high performance programmable home security system using few LDR's as an input sensors. When above sensor(s) get triggered system may dial the user specified phone number (using build-in DTMF generator) and activate the high power audio alarm and lights. All the parameters of DTMF generator, audio alarm and light interface are programmed through the RS232 serial interface.

Current firmware of this system presents interactive control system through the RS232 interface. This control system consist with the menu driven configuration options, self tests, system report generators, etc.

This system also contain 5W (with 4Ω speaker) audio alarm with three selectable tone configurations, which include Police siren, Fire engine siren and Ambulance siren.

Programmable Home Security Alarm System

System Features

  • Touch tone phone dialing interface
  • 5W High powerful audio alarm
  • 2 sensor interface with separate sensitivity adjustments
  • Programmed through the RS232 interface
  • Build-In intelligent light ON/OFF switch

Integrated Circuits

This system uses a Microchip's PIC16F877A as a main controller, LM339 as sensor interface, UM3561 as a tone generator and μPC2002 (TDA2002) as a speaker driver (audio amplifier). LM7805, LM7812 and LM317 voltage regulators are used to obtain +5V, +12V and +3V respectively.

Programmable Home Security Alarm System: schematic
Click to enlarge

The PCB design given with this article makes the assembly much simpler. As PCB contain 230V AC main lines care must be taken while assembling the circuit. As shown in the fig.1 all the photoelectric sensors, some of the switches and alarm speaker are connected with the circuit through the connector bars.

Programmable Home Security Alarm System
Click to enlarge

External connectors and controls

  • DC Power input : Attach DC power supply with 18V - 25V (2A Max.) output.
  • RS232 Connector : Connect RS232 serial cable to the port to configure the system. Do not use RS232 Null Modem cable with this port.
  • PHONE/LINE connector : Attach standard RJ12/RJ11 telephone cable connector to this port. One port is need to use with the phone line and remaining port is for the phone (and it is optional).
  • 3V LASER supply : 3V supply line for LASER diode assembly.
  • Connectors for Sensor 1/2 : Attach high sensitive LDRs for these ports. To get the maximum sensitivity it is recommended to use EG&G VACTEC LDRs.
  • Status Indicator : Indicate run, program and sensor trigger modes.
  • Reset Switch : Press this button to reset entire alarm system. This button enable only when the audible alarm get activated. It is not possible to use this function at the phone dialing/ringer states.
  • Phone dialer enable switch : Turn on this switch to enable the phone dialing feature of this system.
  • Environment Sensor : In-circuit LDR to detect light conditions of the environment.
  • Alarm Volume Control : Use this to control the output power (volume) of the audible alarm.
  • 230V Light connector : Attach 230V AC light (or related peripheral) to these terminals.
  • Tone Selector : Configure the master alarm tone from this jumper as follows,
    • 1-2 : Fire Engine Siren
    • 2-3 : Ambulance Siren
    • Open : Police Siren (Do not connect jumper terminal 1-3, this combination may permanently damage the entire system)
  • Beeper : Produce beeps (e.g: at the input error, etc.)
  • Program / Run Switch connector : Attach switch to this header to select Program or Run mode.
  • Alarm Audio Output : Attach 8Ω (8W) or 4Ω (10W) speaker to this connector.

Parts List

IC1 PIC16F877A
IC2 LM339N
IC3 MAX232
IC4 UM3561
IC5 μPC2002
IC6 LM7805
IC7 LM7812
IC8 LM317
D1 1N4004
D2 1N4148
T1, T3 2SC945
T2 2SD400
Q1 20.00MHz Crystal
Q2 BS170
Q3 IRF9640
R4, R8 30K (LIN) Potentiometr
R6 20K (LIN) Potentiometr
R11 50K (LIN) Potentiometr
R18 50K (LOG) Potentiometr
R1, R2, R3, R19 10K
R5, R7, R9, R10 22K
R12 68K
R13, R14 2.2K
R15 330K
R16, R20 1K
R21, R22, R42 300Ohm
R23, R24, R25, R26,
R27, R28, R29, R30
R31, R32, R33, R34,
R35, R36, R37, R38
R39, R40, R41 47K
R43 240K
L1 4.8 uH Inductor
LD1 5mm Tri-Color LED
SPK 8 Ohm (8W) or 4 Ohm (10W) Speaker
C1, C18, C19 0.1 uF (25V)
C2, C3 10 pF
C11 0.22 uF (100V)
C16, C17 0.33uF (50V)
C4, C5, C6, C7 1uF (50V)
C13, C14 1uF (100V)
C9 10uF (35V)
C10 1000uF (35V)
C12 220uF (35V)
C20 100uF (35V)
C21 470uF (35V)
TRN1 600Ohm:600Ohm Isolation Transformer
SG1 F/QMX Buzzer
RL1 Shinmei RSB-5-S
S1 B3F-10XX-push on switch
S2 M251 SPDT micro switch


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Calibration and Testing in next part

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