low cost high performance programmable home alarm security system

In this project we design low cost high performance programmable home alarm 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.

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

Dilshan R Jayakody – jayakody2000lk@gmail.com

S:http://www.electronics-lab.com/projects/sensors/008/index.html

NE555 Electronic Buzzer Schematic alaram

NE555 Electronic Buzzer Schematic

NE555 Electronic Buzzer Schematic

This accessible cyberbanking buzzer ambit congenital based on timer works for accepting the frequency. The IC timer NE 555 acclimated as astable multivibrator operating at about 1kHz and produces a complete back switched on. The complete abundance can be adapted by capricious the 10K resistor. You may change the 10K resistor with capricious resistor.

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source: skemarangkaian.com

Personal Alarm Small, portable, anti-bag-snatching unit

Small, portable, anti-bag-snatching unit

Also suitable for doors and windows control

Circuit diagram:

Device purpose:

This circuit, enclosed in a small plastic box , can be placed into a bag or handbag. A small magnet is placed close to the reed switch and connected to the hand or the clothes of the person carrying the bag by means of a tiny cord.
If the bag is snatched abruptly, the magnet looses its contact with the reed switch, SW1 opens, the circuit oscillating and the loudspeaker emits a loud alarm sound.
The device can be reverse connected, i.e. the box can be placed in a pocket and the cord connected to the bag.
This device can be very useful in signalling the opening of a door or window: place the box on the frame and the magnet on the movable part in a way that magnet and reed switch are very close when the door or window is closed.

Circuit operation:

A complementary transistor-pair is wired as a high efficiency oscillator, directly driving a small loudspeaker. Low part-count and 3V battery supply allow a very compact construction.

Notes:

• The loudspeaker can be any type, its dimensions are limited only by the box that will enclose it.
• An on-off switch is unnecessary because the stand-by current drawing is less than 20µA.
• Current consumption when the alarm is sounding is about 100mA.
• If the circuit is used as anti-bag-snatching, SW1 can be replaced by a 3.5mm mono Jack socket and the magnet by a 3.5mm. mono Jack plug having its internal leads shorted. The Jack plug will be connected to the tiny cord etc.
• Do not supply this circuit at voltages exceeding 4.5V: it will not work and Q2 could be damaged. In any case a 3V supply is the best compromise.

Parts:

R1____________330K   1/4W Resistor
R2____________100R   1/4W Resistor

C1_____________10nF   63V Polyester or Ceramic Capacitor
C2____________100µF   25V Electrolytic Capacitor

Q1____________BC547   45V 100mA NPN Transistor
Q2____________BC327   45V 800mA PNP Transistor

SW1____________Reed Switch and small magnet (See Notes)

SPKR___________8 Ohm Loudspeaker (See Notes)

B1_____________3V Battery (two A or AA cells wired in series etc.)

8-Zone Water Sensor Alert Kit

Get advance notice of potentially hazardous water leaks in your home or office with a system that alerts you when water buildup is detected. The Waterbug 800 8-Zone Water Sensor Alert Kit can monitor up to eight supervised or 16 non-supervised zones; four supervised sensors are included, additional WaterBug Surface Sensors are available separately. The sensors detector work by forming a conductive bridge between two electrical contacts when it senses the presence of non-flammable conductive liquids.[...]
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Waterbug 800 8-Zone Water Sensor Alert Kit

Water Softener Circuit using NE555

That circuit is based at a technique to remove or neutralize the salt in water, and protect the pipes at home as well as the washing machines or our selves from salt. Its called water softener and its automated circuit using two 555 timers. The cost of parts is nearly 10$ and its very easy to build it.

Read More Source:
http://www.next.gr/inside-circuits/Water-Softener-Circuit-l3484.html