Security alarm

This is Security alarm .If somebody disconnected the wire loop The speaker will generate a sound.I have used a circuit for my land.Then when a robber enter for my land i can know it earlier.when you setup this set the wire loop at the height of 1 feet from the ground.

Security lock

This is so useful circuit for all.This circuit is called security lock.here the pass word of this circuit is 1358.If you like you can change it.After switching on all the numbers circuit will activate.This circuit can be powered with 9V battery.

Sound Generator for Alarm

This is sound generator circuit.You can use this circuit for your alarm circuits.Here I have used common IC 4011.This circuit gives about 10W through a 8 ohm speaker.This circuit can be control (on and off) with sw1.

Security system for doors

This is a security circuit diagram.If someone cross the LED beem.The circuit will be activated.Here I have used red LED insted of the LED you can use Lazer beem too.You can connect a light or 230V alarm for this circuit.but dont pass 500W.If you want more bulbs you can attach them parallely.

Door alarm circuit Diagram

This is a door alarm circuit.I have used a magnetic-reed switch for this.When the door opens the buzzer will give a beep beep sound.Changing R2 and C2 The period of generating beep sound can be changed.According to the values of this circuit you can get that sound for 4 or 5 seconds.double the value the you can double the time.





Note

# this circuit operate with 9V battry.

#Build this circuit on a PCB

Single chip metal detector circuit

This circuit is a Single chip metal detector.Actually we can use this one to detect metals.Specially,I think you have seen some army soldiers keep some thing to detect metals.That equipment has been made through this circuit.so you also can use this to detect metals even bombs





Note

# The IC must be mounted on a holder.

# The switch S1 can be a slide type ON/OFF switch.

# The POT R1 can be used to adjust the sensitivity of the circuit.

Fire Alarm

Here we have used some what different concept.normally we use LDR for light sensitive circuits.but here we use this LDR to detect smoke.I will explain you, how we can do this.first of all we should keep in the kitchen or in a place where the fire can be occurred then keep LDR and the bulb face to face and let smoke to pass between the LDR and the light.when the smoke passes that area it begins to make a sound

Simple Telephone Security Device

This circuit continuously checks the tel. lines and when it detects a misuse, it sounds an alarm. Additionally it transmits a loud disturbing tone through the telephone lines to prevent further misuse. The circuit does not require any external power supply.







When the switch S1 is at the on position, the line voltage at the output of the rectifier diodes is approximately 48V which is enough to exceed the zener's (D5) break down voltage. So the T2 gets forward biassed. As a result the base of T1 is grounded and the remaining part of the circuit doesn't get any supply. In this condition, circuit draws so small current that is negligible and does not effect the normal operation of the telephone line.

When handset of any telephone connected to the line is lifted, the line voltage drops to 10V so T2 is switched off and T1 gets in forward biassed mode. The astable multivibrator circuitry starts oscillating and the speaker starts sounding. The output of the astable multivibrator is also connected to the base of T1 so a loud sound is heard in the ear piece of the unauthorized telephone instrument.

Low cost fire alarm circuit.

When there is a fire breakout in the room the temperature increases.This ultra compact and low cost fire alarm senses fire breakout based on this fact.







Transistor BC177 (Q1) is used as the fire sensor here.When the temperature increases the leakage current of this transistor also increases.The circuit is designed so that when there is an increase in the leakage current of Q1 ,transistor Q2 will get biased.As a result when there is a fire breakout the transistor Q2 will be on.The emitter of Q2 (BC 108)is connected to the base of Q3(AC 128).So when Q2 is ON Q3 will be also ON.The transistor Q3 drives the relay which is used to drive the load ie,light,bell,horn etc as an indication of the fire.The diode D1 is used as a free wheeling diode to protect it from back EMF generated when relay is switche



Notes.

* The Preset R1 can be used to desired temperature level for setting the alarm ON.
* This is not a latching alarm,ie;when the temperature in the vicinity of the sensor decreases below the set point the alarm stops.
* The circuit can be powered using a 9V battery or a 9V battery eliminator.
* All capacitors are electrolytic and must be rated at least 10V.
* The load can be connected through the C,NC,NO points of the relay according to your need.
* The calibration can be done using a soldering iron,and a thermo meter.Switch ON the power supply.Keep the tip of soldering iron near to the Q1.Same time also keep the thermometer close to it.When the temperature reaches your desired value adjust R1 so that relay gets ON.Done!

Telephone off-hook indicator

The circuit depicted here can be used as an indicator when the telephone receiver is off-hook. The circuit can be in corporated with old telephones that does not have such an indicator.






The circuit uses a complementary darling to pair using Q1 (2N3904)and Q2 (2n3906) to sense whether the receiver is off hook and glows a LED to show the condition.



Notes.

* The LED must glow when the circuit is not connected to the telephone line as well as when the telephone is off-hook.
* If the LED does not go OFF when the receiver is restored on hook change the value of R2 so that about 3.5 V comes across it.
* The circuit can be powered from a 3V battery.

Night security light

Here is a simple circuit switches on a light around 2 hours after midnight, the time at which most of the robberies taking place.





This simple circuit is build around a CMOS IC 4060 to obtain the required timing. During day time the LDR has low resistance and keeps the pin 12 of the IC1 high, preventing the IC1 from oscillating. When it is dark the LDR resistance becomes high and the pin 12 of IC1 becomes low and the IC starts oscillating, which indicated by the flashing of LED D3.The values of the timing components R1, R2, C4 are so selected that the out put pin3 of IC1 goes high after 8 hours. That means the high output drives the triac to switch on the lamp around 2’O clock. At morning, the LDR resistance drops and the pin 12 of IC1 goes high and stops the oscillation, making the lamp OFF. The switch S1 can be used to manually ON the lamp. The capacitor C2 prevents false triggering.


Notes.

* Assemble the circuit on a good quality PCB or common board.
* The LDR can be general purpose LDR.
* The light sensitivity can be adjusted using the preset R6.
* The IC1 must be mounted on an IC holder.

Simple Electronic Combination Lock using IC LS 7220

This is the circuit diagram of a simple electronic combination lock using IC LS 7220.This circuit can be used to activate a relay for controlling (on & off) any device when a preset combination of 4 digits are pressed.The circuit can be operated from 5V to 12V.








To set the combination connect the appropriate switches to pin 3,4,5 and 6 of the IC through the header.As an example if S1 is connected to pin 3, S2 to pin 4 , S3 to pin 5, S4 to pin 6 of the IC ,the combination will be 1234.This way we can create any 4 digit combinations.Then connect the rest of the switches to pin 2 of IC.This will cause the IC to reset if any invalid key is pressed , and entire key code has to be re entered.

When the correct key combination is pressed the out put ( relay) will be activated for a preset time determined by the capacitor C1.Here it is set to be 6S.Increase C1 to increase on time.






For the key pad, arrange switches in a 3X4 matrix on a PCB.Write the digits on the keys using a marker.Instead of using numbers I wrote some symbols!.The bad guys will be more confused by this.




Parts List

C1 1 1uF 25V Electrolytic Capacitor
C2 1 220uF 25V Electrolytic Capacitor
R1 1 2.2K 1/4W Resistor
Q1 1 2N3904 NPN Transistor 2N2222
D1 1 1N4148 Rectifier Diode 1N4001-1N4007
K1 1 12V SPDT Relay Any appropriate relay with 12V coil
U1 1 LS7220 Digital Lock IC
S1-S12 12 SPST Momentary Pushbutton Keypad (see notes)
HD1 1 12 Position Header

Digital code lock

This is a simple but effective code lock circuit that has an automatic reset facility. The circuit is made around the dual flip-flop IC CD4013.Two CD 4013 ICs are used here. Push button switches are used for entering the code number. One side of all the push button switches are connected to +12V DC. The remaining end of push buttons 2,3,6,8 is connected to clock input pins of the filp-flops. The remaining end of other push button switches are shorted and connected to the set pin of the filp-flops.




The relay coil will be activated only if the code is entered in correct sequence and if there is any variation, the lock will be resetted. Here is correct code is 2368.When you press 2 the first flip flop(IC1a) will be triggered and the value at the data in (pin9) will be transferred to the Q output (pin13).Since pin 9 is grounded the value is “0” and so the pin 13 becomes low. For the subsequent pressing of the remaining code digits in the correct sequence the “0” will reach the Q output (pin1) of the last flip flop (IC2b).This makes the transistor ON and the relay is energised.The automatic reset facility is achieved by the resistor R11 and capacitor C2.The positive end of capacitor C2 is connected to the set pin of the filp-flops.When the transistor is switched ON, the capacitor C2 begins to charge and when the voltage across it becomes sufficient the flip-flops are resetted. This makes the lock open for a fixed amount of time and then it locks automatically. The time delay can be adjusted by varying the values of R11 and C2






Notes.

* Assemble the circuit on a good quality PCB.
* The circuit can be powered from 12V DC.
* Mount the ICs on holders.
* The L1 can be a 12V, 200 Ohm SPDT relay.
* Capacitor C1 should be tantalum type.
* The C1 and C2 must be rated at least 25V.

Off line Telephone tester

Here is a circuit of an off-line telephone tester which does not require any telephone line for testing a telephone instrument. The circuit is so simple that it can be easily assembled even by a novice having very little knowledge of electronics. A telephone line may be considered to be a source of some 50 volts DC with a source impedance of about 1 kilo-ohm. During ringing, in place of DC, an AC voltage of 70 to 80 volts (at 17 to 25 Hz) is present across the telephone line









When the subscriber lifts the handset, the same is sensed by the telephone exchange and the ringing AC voltage is disconnected and DC is reconnected to the line. Lifting of the handset from the telephone cradle results in shunting of the line’s two wires by low impedance of the telephone instrument. As a result, 50V DC level drops to about 12 volts across the telephone instrument. During conversation, the audio gets superimposed on this DC voltage. Since any DC supply can be used for testing a telephone instrument, the same is derived here from AC mains using step-down transformer X1. Middle point of the transformer’s secondary has been used as common for the two full-wave rectifiers—one comprising diodes D1 and D2 together with smoothing capacitor C1 and the other formed by diodes D3 and D4 along with filter capacitor C2. The former supplies about 12 volts for the telephone instrument through primary of transformer X2 which thus simulates a source impedance, and a choke which blocks AC audio signals present in the secondary of transformer X2. The AF signal available in secondary of X2 is sufficiently strong to directly drive a 32-ohm headset which is connected to the circuit through headphone socket SK1 via rotary switch S2. During ringing, a pulsating DC voltage from transformer X1 via rectifier diode D5, push-to-on switch S3, and contact ‘B’ of rotary switch S2 is applied across secondary of transformer X2. The boosted voltage available across primary of transformer X2 is sufficient to drive the ringer in the telephone instrument. Please avoid pressing of switch S3 for more than a few seconds at a time to prevent damage to the circuit due to high voltage across primary of transformer X2. The circuit also incorporates a music IC (UM66) whose output is connected to secondary of transformer X2 via switch S2 after suitably boosting its output with the help of darlington transistor pair T1 and T2. This output can be used to test the audio section of any telephone instrument. After having assembled the circuit satisfactorily, the following procedure may be followed for testing a telephone instrument:


1. Connect the telephone to the terminals marked ‘To Telephone Under Test’and switch on mains (switch S1).


2. To test the ringer portion, flip switch S2 to position ‘B’ and press S3 for a moment. You should hear the ring in case the ringer circuit of the telephone under test is working. Please ensure that handset is on cradle during this test.


3. For testing the audio section, flip switch S1 to position ‘C’ and connect a headphone to socket SK1. Pick the telephone handset and speak into its microphone. If audio section is working satisfactorily, you should be able to hear your speach via the headphone. If you dial a number, you should be able to hear the pulse clicks or pulse tone in the headphone, depending on whether the telephone under test is functioning in pulse or tone mode. If the telephone under test has a built-in musical hold facility, on pressing the ‘hold’ button you should be able to hear the music. Now flip switch S2 to position ‘A’. You should be able to hear music generated by IC1 through earpiece of the handset of the telephone under test, indicating propor functioning of the AF amplifier section. The circuit can be assembled on a small piece of veroboard. Try to mount the two transformers on opposite sides of the board, displaced by 90 degrees. Always keep handy multi-type modular plugs for testing various types of telephones. Mount all switches, sockets and LEDs on the front of testing panel

Safety Guard

Protect your home appliances from voltage spikes with this simple time delay circuit. Whenever power to the appliances is switched on or resumes after mains failure, the oscillator starts oscillating and D5 blinks. This continues for three minutes. After that, Q14 output of IC CD4060 goes high to trigger the gate of the SCR through D4. At this moment, the voltage is available at the cathode of the SCR, which energizes the relay coil to activate the appliance and D6 glows. Switch SW1 is used for quick start without waiting for delay.









Parts:

R1 = 1M
R2 = 470R
R3 = 820R
R4 = 56K
R5 = 470R
R6 = 1K
R7 = 10K
C1 = 1kuF-25V
C2 = 100nF-63V
C3 = 0.02uF-63V
C4 = 10uF-25V
C5 = 10uF-25V
D1 = 1N4007
D2 = 1N4007
D3 = 1N4007
D4 = 1N4148
D5 = Red LEDs
D6 = Red LEDs
RL1 = 12V Relay
IC1 = AN7809
IC2 = CD4060
SW1 = Switch
T1 = 24V-AC Centre Tapped Transformer



At the heart of the circuit is IC CD4060, which consists of two inverter gates for clock generation and a 14-bit binary ripple counter. Here the clock oscillations are governed by resistor R1 and capacitor C1. In this circuit, only two outputs of the IC (Q5 and Q14) have been used. Q5 is connected to an LED (D5) and Q14 is used to trigger the gate of the SCR through D4 as well as reset the counter. The anode of the SCR is connected to +9V and the cathode is connected to the relay coil. The other pin of the relay coil is connected to the negative supply, while its contacts are used for switching on the appliances.

Powerful Security Siren

This circuit was requested by several correspondents. Its purpose was to obtain more power than the siren circuit already available on this website (One-IC two-tones Siren) and to avoid the use of ICs. A complementary transistor pair (Q2 & Q3) is wired as a high efficiency oscillator, directly driving the loudspeaker. Q1 ensures a full charge of C2 when power is applied to the circuit. Pressing on P1, C2 gradually discharges through R8: the circuit starts oscillating at a low frequency that increases slowly until a high steady tone is reached and kept indefinitely. When P1 is released, the output tone frequency decreases slowly as C2 is charged to the battery positive voltage through R6 and the Base-Emitter junction of Q2. When C2 is fully charged the circuit stops oscillating, reaching a stand-by status.
















Parts:

P1 = SPST Pushbutton Operating Switch R1 = 1K R2 = 10K R3 = 1K R4 = 220R R5 = 10K R6 = 220K R7 = 22K R8 = 100K C1 = 22uF-25V C2 = 22uF-25V C3 = 10nF-63V C4 = 47uF-25V Q1 = BC557 Q2 = BC557 Q3 = BC337 B1 = 12V Battery SW1 = SPST Toggle or Slide Main Switch SPKR = 8 Ohms Loudspeaker


Notes:


* A good sized loudspeaker will ensure a better and powerful output tone. * As stand-by current drawing is zero, SW1 can be omitted and B1 wired directly to the circuit. * Maximum current drawing at full output is about 200mA.

Door Alarm

This circuit emits a beep and/or illuminates a LED when someone touches the door-handle from the outside. The alarm will sound until the circuit will be switched-off.The entire circuit is enclosed in a small plastic or wooden box and should be hanged-up to the door-handle by means of a thick wire hook protruding from the top of the case.A wide-range sensitivity control allows the use of the Door Alarm over a wide variety of door types, handles and locks. The device has proven reliable even when part of the lock comes in contact with the wall (bricks, stones, reinforced concrete), but does not work with all-metal doors.The LED is very useful during setup.







Parts:

R1______________1M 1/4W Resistor
R2______________3K3 1 or 2W Resistor (See Notes)
R3_____________10K 1/2W Trimmer Cermet (See Notes)
R4_____________33K 1/4W Resistor
R5____________150K 1/4W Resistor
R6______________2K2 1/4W Resistor
R7_____________22K 1/4W Resistor
R8______________4K7 1/4W Resistor

C1,C2__________10nF 63V Ceramic or Polyester Capacitors
C3_____________10pF 63V Ceramic Capacitor
C4,C6_________100nF 63V Ceramic or Polyester Capacitors
C5______________2µ2 25V Electrolytic Capacitor
C7____________100µF 25V Electrolytic Capacitor

D1,D2,D4_____1N4148 75V 150mA Diodes
D3_____________5 or 3mm. Red LED

Q1,Q2,Q3,Q5___BC547 45V 100mA NPN Transistors
Q4____________BC557 45V 100mA PNP Transistor

L1_________________ (See Notes)
L2_____________10mH miniature Inductor

Hook_______________ (See Notes)

BZ1___________Piezo sounder (incorporating 3KHz oscillator)

SW1,SW2________SPST miniature Slider Switches

B1_______________9V PP3 Battery

Clip for PP3 Battery


Q1 forms a free-running oscillator: its output bursts drive Q2 into saturation, so Q3 and the LED are off. When part of a human body comes in contact with a metal handle electrically connected to the wire hook, the body capacitance damps Q1 oscillations, Q2 biasing falls off and the transistor becomes non conducting. Therefore, current can flow into Q3 base and D3 illuminates. If SW1 is closed, a self-latching circuit formed by Q4 & Q5 is triggered and the beeper BZ1 is activated.
When the human body part leaves the handle, the LED switches-off but the beeper continues to sound, due to the self-latching behavior of Q4 & Q5. To stop the beeper action, the entire circuit must be switched-off opening SW2.
R3 is the sensitivity control, allowing to cope with a wide variety of door types, handles and locks.

Notes:

* L1 is formed winding 20 to 30 turns of 0.4mm. diameter enameled copper wire on R2 body and soldering the coil ends to the resistor leads. You should fill R2 body completely with coil winding: the final turns' number can vary slightly, depending on different 1 or 2W resistor types actual length (mean dimensions for these components are 13 - 18mm. length and 5 - 6mm. diameter).
* The hook is made from non-insulated wire 1 - 2mm. diameter (brass is well suited). Its length can vary from about 5 to 10cm. (not critical).
* If the device is moved frequently to different doors, Trimmer R3 can be substituted by a common linear potentiometer fitted with outer knob for easy setup.
* To setup the device hang-up the hook to the door-handle (with the door closed), open SW1 and switch-on the circuit. Adjust R3 until the LED illuminates, then turn slowly backwards the screwdriver (or the knob) until the LED is completely off. At this point, touching the door-handle with your hand the LED should illuminate, going off when the hand is withdrawn. Finally, close SW1 and the beeper will sound when the door-handle will be touched again, but will not stop until SW2 is opened.
* In regular use, it is advisable to hang-up and power-on the device with SW1 open: when all is well settled, SW1 can be closed. This precautionary measure is necessary to avoid unwanted triggering of the beeper.

Emergency Light & Alarm

This circuit is permanently plugged into a mains socket and NI-CD batteries are trickle-charged. When a power outage occurs, the lamp automatically illuminates. Instead of illuminating a lamp, an alarm sounder can be chosen.When power supply is restored, the lamp or the alarm is switched-off. A switch provides a "latch-up" function, in order to extend lamp or alarm operation even when power is restored.








Parts:
R1____________220K 1/4W Resistor R2____________470R 1/2W Resistor R3____________390R 1/4W Resistor R4______________1K5 1/4W Resistor R5______________1R 1/4W Resistor R6_____________10K 1/4W Resistor R7____________330K 1/4W Resistor R8____________470R 1/4W Resistor R9____________100R 1/4W Resistor C1____________330nF 400V Polyester Capacitor C2_____________10µF 63V Electrolytic Capacitor C3____________100nF 63V Polyester Capacitor C4_____________10nF 63V Polyester Capacitor D1-D5________1N4007 1000V 1A Diodes D6______________LED Green (any shape) D7___________1N4148 75V 150mA Diode Q1,Q3,Q4______BC547 45V 100mA NPN Transistors Q2,Q5_________BC327 45V 800mA PNP Transistors SW1,SW2________SPST Switches SW3____________SPDT Switch LP1____________2.2V or 2.5V 250-300mA Torch Lamp Bulb SPKR___________8 Ohm Loudspeaker B1_____________2.5V Battery (two AA NI-CD rechargeable cells wired in series) PL1____________Male Mains plug Mains voltage is reduced to about 12V DC at C2's terminals, by means of the reactance of C1 and the diode bridge (D1-D4). This avoids the use of a mains transformer. Trickle-charging current for the battery B1 is provided by the series resistor R3, D5 and the green LED D6 that also monitors the presence of mains supply and correct battery charging. Q2 & Q3 form a self-latching pair that start operating when a power outage occurs. In this case, Q1 biasing becomes positive, so this transistor turns on the self latching pair. If SW3 is set as shown in the circuit diagram, the lamp illuminates via SW2, which is normally closed; if set the other way, a square wave audio frequency generator formed by Q4, Q5 and related components is activated, driving the loudspeaker. If SW1 is left open, when mains supply is restored the lamp or the alarm continue to operate. They can be disabled by opening the main on-off switch SW2. If SW1 is closed, restoration of the mains supply terminates lamp or alarm operation, by applying a positive bias to the Base of Q2.
Notes: * Close SW2 after the circuit is plugged. * Warning! The circuit is connected to 230Vac mains, then some parts in the circuit board are subjected to lethal potential!. Avoid touching the circuit when plugged and enclose it in a plastic box.

Personal Alarm

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 starts 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.






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.) 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.

FM Telephone Bug

This is a simple transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM radio. The frequency can be tuned from 88 to about 94Mhz and the range is about 200 feet. It is extremely easy to build and is therefore a good, useful beginner project..

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Parts R1 180 Ohm 1/4 W Resistor R2 12K 1/4 W Resistor C1 330pF Capacitor C2 12pF Capacitor C3 471pF Capacitor C4 22pF Capacitor Q1 2SA933 Transistor D1, D2, D3, D4 1SS119 Silicon Diode D5 Red LED S1 SPDT Switch L1 Tuning Coil MISC Wire, Circuit Board Notes 1. L1 is 7 turns of 22 AWG wire wound on a 9/64 drill bit. You may need to experiment with the number of turns. 2. By stretching and compressing the coils of L1, you can change the frequency of the transmitter. The min frequency is about 88 Mhz, while the max frequency is around 94 Mhz. 3. The green wire from the phone line goes to IN1. The red wire from the phone line goes to IN2. The green wire from OUT1 goes to the phone(s), as well as the red wire from OUT2. 4. The antenna is a piece of thin (22 AWG) wire about 5 inches long. 5. All capacitors are rated for 250V or greater. 6. The transmitter is powered by the phone line and is on only when the phone is in use. S1 can be used to turn the transmitter off if it is not needed. 7. If you have problems with the LED burning out, then add a 300 ohm 1/4W resistor in series with it.