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.

Note

# Build this on a pcb

# This circuit operates with 9V power

Broken Charger Connection Alarm Circuit

The above circuit can be useful to detect if the load of any battery charger or plug-in adapter supply is not properly connected. The load can be a set of batteries to be charged or any other type of battery or low dc voltage operated device. The circuit can safely operate over a 3 to 15V range and 1A max. Current, provided the supply voltage is about one volt higher than the voltage required by the load.The circuit is inserted between the supply and the load; therefore, until a trickle-charging current of at least 100µA is flowing towards the load, D1 and D2 will conduct. The forward voltage drop (about 1V) available across the Diodes drives Q2 into conduction and, consequently, Q1 will be cut-off. If no appreciable load is connected across the circuit's output, Q2 will become cut-off, Q1 will conduct and the Piezo-sounder will beep.


Parts:

R1 = 10K R2 = 1K R3 = 1K Q1 = BC557 Q2 = BC557 D1 = 1N4007 D2 = 1N4007 D3 = Red LED BZ1 = Piezo Sounder


Notes:

* An optional LED and its series limiting resistor can be wired in parallel to BZ1, as shown in dotted lines in the circuit diagram. * In this case you may omit the Piezo-sounder in order to obtain a visual alert only

Zero degree Celsius alarm

his is a circuit of Zero degree Celsius alarm . this is very useful circuit for all.Because we all can get different uses from this circuit.When you fix this circuit You have to face to a problem it is none but the power supply.Here I have given a power supply so you can avoid that problem.

Siren for Factories

This is powerful siren circuit diagram.You can get lots of supports from this circuit because you can use this circuit for your alarm circuit then you will be able to get maximum results.


Note

This circuit can be operated with 12V power supply.

Siren for Factories ( 2

This is a siren circuit diagram But this circuit is little bit different.Because this circuit can generate up to 6W power here I have used famous IC 4011

Note

# This circuit operates with 12v power supply

#this get about 1A current

Car Alarm Arming Horn Beep Canceller electronic circuit diagram

It's a great convenience that most modern cars come with a built in alarm, however it is nothing but noise pollution that the horn sounds when the alarm is armed. Disconnecting the alarm system from the horn relay will eliminate this, but prevent the horn from sounding in the even of an actual alarm. This circuit serves to silence the arming beep yet maintain the alarm by introducing a small delay into the signal. It sits between the alarm and horn relay. The alarm must provide a constant horn signal for at least 3 seconds before the horn relay is activated. That way the quick "beep" will never activate the horn relay, while the constant alarm signal will.

Parts

C1 0.01uF Ceramic Disc Capacitor
C2 100uF 35V Electrolytic Capacitor
R1 1K 1/4W Resistor
R2 10K 1/4W Resistor
R3 15K 1/4W Resistor
R4 470 Ohm 1/4W Resistor
D1, D3, D4 1N4004 Rectifier Diode
D2 Red LED
U1 555 Timer IC
K1 SPST 12V Automotive Relay
MISC Board, Wire, Socket For U1, Case

bc550-high-temperature-alarm

The circuit is small regulatorof temperature, us warns for the increase of temperature. The control of temperature becomes from the thermistor TH1, that is negative factor. His resistance is altered between in the 10K in temperature 25° C and roughly in the 1K in their 94° C. The trimmer TR1 regulates the precise temperature in which the Q1-2, connected as darlington, conduct, making him relay K1 close also the buzzer BZ, sound. The alarm is activated when the temperature becomes bigger than predetermining. The thermistor it should he is placed far from the remainder circuit, in order that this is not in danger from the temperature. The supply of circuit becomes from battery 9V, but if he is placed in constant place, then we can him supply with one power supply . In the contacts of relay we can connect what load we want, as a lamb, other circuit k.a. Also can is added a LED, if we want to have also optical clue of excitation. The regulation becomes sinking him thermistor TH1, in water which we know the temperature of (the contacts should are well insulate so that do not have short-circuit) and regulating him trimmer, until excited the circuit. The cable that we connect the circuit with the TH1, should be plate.

Fire Alarm Circuit Using LDR

Fire Alarm Circuit Using LDR

Here is a simple fire alarm circuit based on a LDR and lamp pair for sensing the fire.The alarm works by sensing the smoke produced during fire.The circuit produces an audible alarm when the fire breaks out with smoke.

When there is no smoke the light from the bulb will be directly falling on the LDR.The LDR resistance will be low and so the voltage across it (below .6V).The transistor will be OFF and nothing happens.When there is sufficient smoke to mask the light from falling on LDR, the LDR resistance increases and so do the voltage across it.Now the transistor will switch to ON.This gives power to the IC1 and it outputs 5V.This powers the tone generator IC UM66 (IC2) to play a music.This music will be amplified by IC3 (TDA 2002) to drive the speaker.

The diode D1 and D2 in combination drops 1.4 V to give the rated voltage (3.5V ) to UM66 .UM 66 cannot withstand more than 4V.
* The speaker can be a 8Ω tweeter.
* POT R4 can be used to adjust the sensitivity of the alarm.
* POT R3 can be used for varying the volume of the alarm.
* Any general purpose NPN transistor(like BC548,BC148,2N222) can be used for Q1.
* The circuit can be powered from a 9V battery or a 9V DC power supply.
* Instead of bulb you can use a bright LED with a 1K resistor series to it

/low-cost-fire-alarm-circuit-using transistor

Here's a cheap fire alarm circuit for building one. 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 switched.


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,NC 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!

light-sensitive-alarm

The Alarm circuit detects a sudden shadow falling on the light-sensor and sounds the bleeper when this happens. The circuit will not respond to gradual changes in brightness to avoid false alarms. The bleeper sounds for only a short time to prevent the battery running flat. Normal lighting can be used, but the circuit will work best if a beam of light is arranged to fall on the light-sensor. Breaking this beam will then cause the bleeper to sound. The light sensor is an LDR (light-dependant resistor), this has a low resistance in bright light and a high resistance in dim light.


- The light-sensitivity of the circuit can be adjusted by varying the 100k preset.
- The length of bleep can be varied from 0.5 to 10 seconds using the 1M preset.

Using the 7555 low-power timer ensures that the circuit draws very little current (about 0.5mA) except for the short times when the bleeper is sounding (this uses about 7mA). If the circuit is switched on continuously an alkaline PP3 9V battery should last about a month, but for longer life (about 6 months) you can use a pack of 6 AA alkaline batteries

5zone-alarm-circuit

Each zone alarm uses a normally closed contact. These can be micro switches or standard alarm contacts (usually reed switches). Zone 1 is a timed zone which must be used as the entry and exit point of the building. Zones 2 - 5 are immediate zones, which will trigger the alarm with no delay. Some RF immunity is provided for long wiring runs by the input capacitors, C1-C5. C7 and R14 also form a transient suppresser. The key switch acts as the Set/Unset and Reset switch.

For good security this should be the metal type with a key. At switch on, C6 will charge via R11, this acts as the exit delay and is set to around 30 seconds. This can be altered by varying either C6 or R11. Once the timing period has elapsed, LED6 will light, meaning the system is armed. LED6 may be mounted externally (at the bell box for example) and provides visual indication that the system has set. Once set any contact that opens will trigger the alarm, including Zone 1.

To prevent triggering the alarm on entry to the building, the concealed re-entry switch must be operated. This will discharge C6 and start the entry timer. The re-entry switch could be a concealed reed switch, located anywhere in a door frame, but invisible to the eye. The panic switch, when pressed, will trigger the alarm when set. Relay contacts RLA1 provide the latch, RLA2 operate the siren or buzzer.

Simple Home Alarm System

Simple Home Alarm System

This Home Alarm System is simple, secure, fast and cheap. It's only few components with maximum security with Rolling Code TX and Shock Sensor with variable sensitivity. The alarm module can be assembled in only 2 hours and it don't need manual preset.

Home Alarm System with this characteristics is the most cheap system and the total cost could be reduced using a normal external sounder (escl. AG8).GSM module will be add in the future for a remote control.

The blue led connected to the pin RA3 of micro controller is used like a memory to know if the home alarm system has been activated by an event and its reset after a reactivation. The red led connected to the power supply before the 1N5406 diode is used to check the power supply connection. Of course the other 3 micro led red near the relays are used to check the output state.

Here you can download the last version of The Home Alarm System date 10 July 2007:

source
binary (hex)

basic-phototransistor-detector

This is a Phototransistor Detector circuit. In this circuit, when the light falling on the phototransistor (Q1) is blocked, its conductance will decrease and the voltage across Q1 will rise. When the voltage rises above 1/2 of the supply voltage the output of the comparator will turn ON and the LED will be lit.

The only critical part of this circuit is the value of resistor R1 which in most cases can be 470K ohms but may have to be increase if the room is dark or decreased if the room is well lit.

Increasing the value of R1 will cause the sensitivity of the sensor to decrease. This may be necessary when the light falling on the cell is not very strong or shadows can affect the phototransistor.

There are a number of phototransistors sizes and case styles. The smaller cases will be easier to hide but connecting wires may be more difficult.

basic-cds-photocell-detector

This is a Basic Cadmium Sulfide (Cds) Photocell Detector circuit. In this circuit, when the light falling on the photocell (PC 1) is blocked, its resistance will increase and the voltage across PC 1 will rise. When the voltage rises above 1/2 of the supply voltage the output of the comparator will turn ON and the LED will be lit.

Due to wide variations in CdS photocells it is usually best to install the cell and then measure its resistance under normal lighting conditions. A resistor with a value that is approximately 3 to 5 times the measured resistance of the cell is then selected for R1. For example; If the cell resistance is measured at 400 ohms then a 1200 to 2200 ohms resistor would be used.

Increasing the value of R1 will cause the sensitivity of the sensor to decrease. This may be necessary when the light falling on the cell is not very strong or shadows can affect the photocell.

This Photocell Detector circuit can be adapted for use in dark areas by placing a small light above the photocell

infrared-light-photo-detector-circuit

This is a basic infrared light photo detector circuit. In this circuit the light falling on the phototransistor will be from an Infrared Light Emitting Diode (IrLED) but otherwise it is the same as the phototransistor circuit shown above.

When the light falling on the phototransistor (Q1) is blocked, its conductance will decrease and the voltage across Q1 will rise. When the voltage rises above 1/2 of the supply voltage the output of the comparator will turn ON and the LED will be lit

lie-detector-circuit

This detector circuit is for detecting a Lie. The lie detector circuit diagram consists of three transistors, a capacitor, two lights or LEDs, five resistors, and a variable resistor.

This Lie Detector circuit is based on the fact that a person's skin resistance changes when they sweat (sweating because they're lying). Dry skin has a resistance of about 1 million ohms, whereas the resistance of moist skin is reduced by a factor of ten or more.

Resistors R1 and R2 form a voltage divider. They have resistances of 1 000 000 ohms (1 mega ohms) and, because their values are equal, the voltage at the upper probe wire is half the battery voltage (about 4.5 volts).

A person holding the probe wires will change the voltage at the upper probe wire depending on their skin resistance. The skin resistance is in parallel with R2 and, because it is likely to be similar to or smaller than R2, the voltage at the probe wire will fall as skin resistance falls.

Capacitor C1 functions as a smoothing capacitor and removes the 50Hz induced mains hum that is found on a person's body.

TR1 and R3 form a buffer circuit (called an emitter-follower). The voltage at the emitter of TR1 follows the voltage at the probe wire and is now able to drive transistor TR2.

Transistors TR1 and TR2 act as a voltage comparator. If the voltage at the base of TR2 is higher than at the base of TR3 then the green LED (L1) will come on. If the reverse is true then the red LED (L2) will light.

To test the Lie Detector hold the probe wires. Adjust VR1 until the green LED is just on and the red LED is just off. This is the point at which the voltage at the base of TR2 is just greater than at the base of TR3. Now use moist fingers to hold the probes. This lowers the skin resistance and causes the voltage at the base of TR2 to fall. The voltage at the base of TR3 is now greater and the red LED comes on.

How to Use the Lie Detector

The Lie Detector needs tuning before it can be used, and it needs tuning for every person that uses it as everyone has slightly different skin.

Touch the two probe wires against the palm of your (dry) hand, such that the metal ends are a couple of centimeters apart (the metal ends must not touch each other). Adjust the tuning control (VR1) until the red light (FALSE) just goes out. The Lie Detector is now tuned for your skin. If you lick your palm and touch the wires against it again, the red light should come on brightly.

You should now understand how to use the Lie Detector to detect a real lie. Touch the two probe wires against the palm of the subject's hand and adjust the tuning control as before until the red light just goes out. When the subject tells a lie, and begins to sweat, the red light will get brighter.

It must be emphasized that the Lie Detector won't detect every lie, as it is really only a sweat detector. It only detects lies that have consequences to being told, lies that cause the subject to sweat (with fear). Pretend or 'joke' lies won't have any effect.

The Lie Detector has a number of other uses, detailed below, and it could perhaps more accurately be described as an 'Experiment Machine'.

Use lie detector to test the conductivity of the human body. Get a group of people to hold hands in a circle with the two probes of the Lie Detector as part of the circle. See how many bodies the current will flow through to make the red LED light.
Testing the conductivity of objects. For example, metals, plastics, wood, hair, the lead of a pencil. If a material is conductive then touching the lie detector probe wires against it will make the red LED light.
Determining whether a houseplant needs watering. Touch the lie detector probe wires against the soil. If the green LED stays on, the plant needs watering. If the red LED comes on, the soil is sufficiently moist.
Determining whether a cake is cooked. Press the lie detector probe wires into the surface of the cake. If the red LED comes on then the cake is still moist and needs further cooking

lie-detector-circuit-

This lie detector circuit can be built in a few minutes, but can be incredibly useful when you want to know if someone is really telling you the truth. It is not as sophisticated as the ones the professionals use, but it works. It works by measuring skin resistance, which goes down when you lie.

Parts List:

R1 - 33K 1/4W Resistor
R2 - 5K Pot
R3 - 1.5K 1/4W Resistor
C1 - 1uF 16V Electrolytic Capacitor
Q1 - 2N3565 NPN Transistor
M1 - 0-1 mA Analog Meter
MISC - Case, Wire, Electrodes (See Notes)

Notes:

The electrodes can be alligator clips (although they can be painful), electrode pads (like the type they use in the hospital), or just wires and tape.
To use the circuit, attach the electrodes to the back of the subjects hand, about 1 inch apart. Then, adjust the meter for a reading of 0. Ask the questions. You know the subject is lying when the meter changes.

chris-eves-bat-detector-circuit

This Bat Detector Circuit is authored by Chris Eve. Basic tests with a variety of salvaged electret microphones all showed good response to 50kHz and beyond, the smaller the unit the better the response. My tests indicate that a small electret microphone has at least some response to 100kHz and that this response is reasonably "flat" to at least 50kHz.

The microphone I use is approximately 6mm in diameter and can be mounted within the body of a 3.5mm jack plug. Having the microphone socketed rather than fixed within the detector case is optional, but gives further opportunity to experiment with uni-directional or "Pressure Zone" modules (see below), or other microphones mounted remotely from the electronics.

This bat detector circuit to have better sensitivity, both in distance to a visible bat and in audio frequency, than some other published circuits using a 40kHz transducer with 4000x gain amplification, though the 40kHz transducer I used for the comparison may have a bearing on these results.

The high-pass filter is included purely to help eliminate the circuit being triggered by ambient noise. The filter is a 4-pole Chebychev with a very steep roll-off below 15kHz. There is virtually zero response at 10kHz and below. This type of circuit relies on the wanted signal being loud enough to trigger the CMOS counter, so the less unwanted signal that reaches the circuit the better. Whilst any of the basic circuits based around a 40kHz transducer will perform adequately for the detection of bats calling within that frequency range, which includes many of the more common species, this circuit will give much better indication of the presence of less-common bats that call at lower frequencies, around 20kHz, as well, hopefully, those at somewhat higher frequencies.

When used at dusk, when individual bats are still visible, pointing a unidirectional microphone at a solitary bat indicates a usable range of at least 100ft (30m). Bats actually call very loudly indeed ... it's probably a good job we cannot hear them, else they would keep us awake!

This circuit was built in a metal box, because that was what I had to hand, using point-to-point wiring on a ground-plane. Perforated strip-board should be perfectly adequate and probably a lot easier to fault-find should you make a mistake. I do not have nor intend to produce a pcb layout, so please do not ask for one, though if you should feel the need to produce one and have the inclination to share it I would be only too willing to include it (or a link to it) on this page. The circuit may be more susceptable to interference from electronic sources if built in a plastic container. Current consumption is around 15mA with no audio output, so a PP3 battery should last for several evenings unless you have got a lot of bats in your area. For regular or extended use, rechargeable batteries or an external power source would make sense. Note that the LM386 has an absolute maximum voltage of 15v (12v recommended), but the rest of the circuit is OK to 15v. Also be aware, if tempted to use a regulated supply incorporating a 78xx series regulator, that these do generate a lot of noise, so extra filtering could be necessary, especially on the microphone supply. Component choice for the high-pass filter section is critical for good results, close-tolerance low-noise resistors and capacitors should be used to achieve the expected performance. Similar low-noise components should also be used in the rest of the circuit, (no carbon resistors!), though the tolerances are less critical elsewhere.

Having the microphone and loudspeaker both mounted on/in the detector itself can result in unwanted feedback limiting the volume the speaker can be used at. With the microphone mounted on the detector, simply handling the unit can cause audio output, though this can be reduced to a minimum if the unit is held firmly and moved gently. Remote mounting of the speaker and/or microphone, the use of a uni-directional microphone module (also helpful to determine where the bat is or for listening to an individual bat), or at least having the speaker facing away from the microphone, all help reduce/eliminate feedback, making it easier to share the experience with others.

ultrasonic-radar

This is a ultrasonic radar project with many practical applications in security and alarm systems for homes, shops and cars. It consists of a set of ultrasonic receiver and transmitter which operate at the same frequency. When something moves in the area covered by the circuit the circuit’s fine balance is disturbed and the alarm is triggered. The circuit is very sensitive and can be adjusted to reset itself automatically or to stay triggered till it is reset manually after an alarm.

Adjustments
This kit does not need any adjustments, if you follow the building instructions.

Warning
If they are used as part of a larger assembly and any damage is caused, our company bears no responsibility.

While using electrical parts, handle power supply and equipment with great care, following safety standards as described by international specs and regulations.

If it does not work
Check your work for possible dry joints, bridges across adjacent tracks or soldering flux residues that usually cause problems. Check again all the external connections to and from the circuit to see if there is a mistake there.

See that there are no components missing or inserted in the wrong places.
Make sure that all the polarised components have been soldered the right way round. Make sure that the supply has the correct voltage and is connected the right way round to your circuit. Check your project for faulty or damaged components.

If everything checks and your project still fails to work, please contact your retailer and the Smart Kit Service will repair it for you.

Parts List
R1 = 180 KOhm C1, 6 = 10uF/16V TR1, 2, 3 = BC547 , BC548
R2 = 12 KOhm C2 = 47uF/16V P1 = 10 KOhm trimmer
R3, 8 = 47 KOhm C3 = 4,7 pF P2 = 47 KOhm trimmer
R4 = 3,9 KOhm C4, 7 = 1 nF IC1, 2 = 741 OP-AMP
R5, 6, 16 = 10 KOhm C5 = 10nF IC3 = 4093 C-MOS
R7, 10, 12, 14, 17 = 100 KΩ C8, 11 = 4,7 uF/16V R = TRANSDUCER 40KHz
R9, 11 = 1 MOhm C9 = 22uF/16V T = TRANSDUCER 40KHz
R13, 15 = 3,3 KOhm C10 = 100 nF D1, 2, 3, 4 = 1N4148
C12 = 2,2 uF/16V
C13 = 3,3nF
C14 = 47nF

biscuit-tin-alarm

Someone is stealing the biscuits! Your mission, should you choose to accept it, is to design a circuit which will give an audible alarm as soon as the biscuit tin is opened. The circuit provides a delay of around 10 seconds when the power supply is first connected during which the circuit can be placed in the tin. After this, if the LDR is exposed to light the alarm is triggered and remains ON, producing a penetrating high pitched sound until the power is disconnected.
Prototype board testing leads eventually to a complete circuit for the device being developed. You can continue to make small alterations until the circuit behaves in the way you want.

The sensor detects the opening of the tin. The output of the sensor triggers the latch so that its output goes HIGH. The reset subsystem provides some way of silencing the alarm.