ffd

You can use this laser-based intruder alarm conveniently at the entrance of a hall or any other similar location to protect the same from unauthorised access as and when desired. Its range can be extended further to protect the perimeter of a  building from unauthorised intrusion by using a cascade arrangement of multiple alarms. The circuit consists of a transmitter and a receiver. Circuit diagram : Fig. 1: Transmitter circuit Diagram The transmitter circuit (shown in  Fig. 1) is nothing but a laser diode (LD1) driven by a 9V PP3 battery. The  output of IC1 is regulated 5V as long as  its input remains equal to or more than  7.5V, thus ensuring a constant drive  current for the laser diode. The battery (Batt1) is connected to the circuit  through switch S1. The laser diode (LD1) can be  replaced with a laser pointer (torch)  emitting red laser beam. The laser  pointer itself can be used as a transmitter. The pointer has in-built series  resistance, on/off switch and battery. Ci...

The alarm may be used for a variety of applications, such as frost monitor, room temperature monitor, and so on. In the quiescent state, the circuit draws a current of only a few microamperes, so that, in theory at least, a 9 V dry battery (PP3, 6AM6, MN1604, 6LR61) should last for up to ten years. Such a tiny current is not possible when ICs are used, and the circuit is therefore a discrete design.  Every four seconds a measuring bridge, which actuates a Schmitt trigger, is switched on for 150 ms by a clock generator. In that period of 150 ms, the resistance of an NTC thermistor, R11, is compared with that of a fixed resistor. If the former is less than the latter, the alarm is set off.  When the circuit is switched on, capacitor C1 is not charged and transistors T1–T3 are off. Circuit diagram : General-Purpose Alarm Circuit Diagram   After switch-on, C1 is charged gradually via R1, R7, and R8, until the base voltage of T1 exceeds the threshold bias.  transistor T1 then comes on and...

This Simple Cmos Motorcycle Alarm Circuit Diagram features an intermittent siren output and automatic reset. It can be operated manually using a key-switch or a hidden switch; but it can also be wired to set itself automatically when you turn-off the ignition. By adding external relays you can immobilize the bike - flash the lights etc. Cmos Motorcycle Alarm Schematic Diagram     Notes Any number of normally-open switches may be used. Fit "tilt" switches that close when the steering is moved or when the bike is lifted off its side-stand or pushed forward off its centre-stand. Use micro-switches to protect removable panels and the lids of panniers etc. Once activated - the rate at which the siren switches on and off is controlled by R9 & C5. For example - increasing the value of C5 will slow it down - while reducing the value of R9 will make it faster. While at least one switch remains closed the siren will sound. About thirty seconds after all of the switches have been ...

This is a simple circuit that activates an alarm when there is a knock on the door or there are any vibrations due to movement of heavy goods or furniture. The circuit uses readily available components. Circuit and working The circuit is built around quad-opamp LM324 (IC1), which is configured in amplifier mode. It uses the piezoelectric element of a piezo buzzer as the input sensor, two transistors BC547 (T1 through T2), a piezo buzzer and some other components for the alarm circuit. Fig. 1 shows the circuit diagram of the door-knock alarm. The reference voltage at pin 3 of IC1 is set by trimming potmeter VR1. The piezoelectric element plate is fixed at the centre of the door using cello tape. Apply a small quantity of adhesive on the edges between the plates. Wires from the piezo element are connected at CON2. These generate an input pulse when vibrations are caused by knocking on the door. The pulse is amplified by op-amp A1 of IC1. Remaining three op-amps of quad IC LM324 are not u...

The circuit uses a 555 timer wired as an astable oscillator and powered by the emitter current of the BC109C. Under dry conditions, the transistor will have no bias current and be fully off. As the probes get wet, a small current flows between base and emitter and the transistor switches on. A larger current flows in the collector circuit enabling the 555 osillator to sound. Simple Water Activated Alarm  Circuit diagram : An On/Off switch is provided and remember to use a non-reactive metal for the probe contacts. Gold or silver plated contacts from an old relay may be used, however a cheap alternative is to wire alternate copper strips from a piece of veroboard. These will eventually oxidize over but as very little current is flowing in the base circuit, the higher impedance caused by oxidization is not important. No base resistor is necessary as the transistor is in emitter follower, current limit being the impedance at the emitter (the oscillator circuit).

Description: This is a simple single-zone burglar alarm circuit. Its features include automatic Exit and Entry delays and a timed Bell/Siren Cut-Off. It's designed to be used with the usual types of normally-closed input devices such as - magnetic reed contacts - micro switches - foil tape - and PIRs. But it can be Easily Modified to accept normally-open triggering devices - such as pressure mats. Circuit Diagram   Notes:   It's easy to use. First check that the building is secure and that the green LED is lit. Then move SW1 to the "set" position. The red LED will light. You now have about 30 seconds to leave the building. When you return and open the door - the Buzzer will sound. You then have about 30 seconds to move SW1 to the "off" position. If you fail to do so - the relay will energize and the Siren will sound. While at least one of the switches in the normally-closed loop remains open - the Siren will continue to sound. However, about 15-minutes aft...

This is a circuit of an alarm residential sectors 5, or 5 areas that are monitored separately, it also has a panic button, timing system, is powered by the network jointly by battery v. 12. It is very simple and uses only three integrated circuits and transistors.  Simple Alarm Residential 5 sectors Circuit Diagram

OVER LIGHT DETECTOR Here i am going to Introduce you an Excess light Detector or sensor circuit. The sensing component used in this circuit is LDR (Light Dependent Resistor). LDRs are sensitive, inexpensive and readily available device. They posses good power and voltage handling capacity similar to an ordinary resistor. CIRCUIT DIAGRAM OF OVER LIGHT DETECTOR Components required to wire up this circuit 1. LDR 2. R - 1K 3. SCR 4. Buzzer 5. 5V BATTERY WORKING PRINCIPLE OF OVER LIGHT DETECTOR The LDR is a variable resistor whose resistance decreases with increase in light intensity. When the light falling on an LDR has normal intensity, its Resistance is large enough and the voltage across R is insufficient to trigger the SCR. However, when light falling on LDR is of large intensity, the Resistance of LDR falls and voltage drop across R becames large enough to trigger the SCR. Consequently the buzzer sounds the alarm. It may be noted that if the strong light disappears the buzzer continu...

Description The alarm may be used for a variety of applications, such as frost monitor, room temperature monitor, and so on. In the quiescent state, the circuit draws a current of only a few microamperes, so that, in theory at least, a 9 V dry battery (PP3, 6AM6, MN1604, 6LR61) should last for up to ten years. Such a tiny current is not possible when ICs are used, and the circuit is therefore a discrete design. Every four seconds a measuring bridge, which actuates a Schmitt trigger, is switched on for 150 ms by a clock generator. In that period of 150 ms, the resistance of an NTC thermistor, R11, is compared with that of a fixed resistor. If the former is less than the latter, the alarm is set off. When the circuit is switched on, capacitor C1 is not charged and transistors T1–T3 are off. After switch-on, C1 is charged gradually via R1, R7, and R8, until the base voltage of T1 exceeds the threshold bias. Transistor T1 then comes on and causes T2 and T3 to conduct also. Thereupon, C1 is...

The author wanted a very cheap and simple alarm for some of his possessions, such as his electrically assisted bicycle. This alarm is based on a cheap window alarm, which has a time-switch added to it with a 1-minute time-out. The output  pulse of the 555 replaces the reed switch in the window alarm. The 555 is triggered by a sensor mounted near the front  wheel, in combination with a magnet that is mounted on the spokes. This sensor and the magnet were taken from a cheap bicycle computer.  Cheap Bicycle Alarm Schematics Circuit diagram : Cheap Bicycle Alarm Circuit Diagram The front wheel of the bicycle is kept unlocked, so that the reed  switch closes momentarily when the wheel turns. This  triggers the 555, which in turn activates the window alarm. The circuit around the 555 takes very little current and can  be powered by the batteries in the window alarm.  There  is just enough room  left inside the enclosure of the window  alarm t...

BURGLAR ALARM USING IC TIMER 555/556 ELECTRONIC DIAGRAM circuit diagram of burglar alarm using IC timer 555/556 is functioned as an alarm to prevent thief entering your house. The alarm would produce loud sound when a thin wire connecting resistor R1 with IC pin no 4 is broken. Thin fiber is used as the wire. The thinner the wire, the more responsive the alarm. This circuit needs 5-15V power supply, buzzer is used as a speaker. Here is the circuit schematic : Parts list :     Resistor R1 : 10k     Resistor R2 : 68k     Resistor R3 : 1k     Polar capacitor C1 : 1uF/15 B     Capacitor C2-C3 : 0.01uF     IC Timer : NE555

This is the simple Personal alarm Circuit Diagram. Small, portable, anti-bag-snatching unit Also suitable for doors and windows control Circuit diagram 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.) 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 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 connec...

The author wanted a very cheap and simple alarm for some of his possessions, such as his electrically assisted bicycle. This alarm is based on a cheap window alarm, which has a time-switch added to it with a 1-minute time-out. The output  pulse of the 555 replaces the reed switch in the window alarm. The 555 is triggered by a sensor mounted near the front  wheel, in combination with a magnet that is mounted on the spokes. This sensor and the magnet were taken from a cheap bicycle computer. Circuit diagram : Cheap Bicycle Alarm Circuit Diagram The front wheel of the bicycle is kept unlocked, so that the reed  switch closes momentarily when the wheel turns. This  triggers the 555, which in turn activates the window alarm. The circuit around the 555 takes very little current and can  be powered by the batteries in the window alarm.  There  is just enough room  left inside the enclosure of the window  alarm to mount the time-switch inside it. The result is a very cheap, compact devic...

This is simple Simple Alarm Power Supply Circuit Diagram. A 12 Volt power suppiled designed for Ron's Modular Burglar Alarm. However, being a popular supply voltage this circuit will have many other uses as well. Simple Alarm Power Supply Circuit Diagram Notes This Power Supply is suitable for the Modular Burglar Alarm. However, it has other applications. It is designed to provide an output of 12-volts, with a current of up to 1-amp. In the event of mains failure, the back-up battery takes over automatically. When the mains is restored, the battery recharges. Use a genuine alarm type back-up battery. They are maintenance-free, and their terminals can be held at 13v8 for many years, with no ill effects. A smaller or larger capacity battery may be used, without circuit modification. Use the 2-amp version of the 7805. It needs the larger heatsink because it has to dissipate a lot of energy, especially when called upon to recharge a flat battery. This heatsink is at 9v1, and must NOT b...

The door opener derives its power from a 9-V battery. A momentary-contact switch, 52, is provided in the event that manual opening and closing is required. Relay Kl is a 9-V type and relay K2 is a 117`Vac latching-type, which automatically latches with the first burst of current and opens on the second burst. Door Opener Alarm Circuit Diagram The gate lead of the LASCR is not used; a light source triggers the LASCR unit into conduction, causing current to flow in the coil of the relay. That, in turn, causes Kl`s contacts to close, thereby energizing K2 (closing its contacts), and operating the garage door motor.

This is a Bar Display With Alarm Flasher Schematic Project. Hello Freinds ! Here designed SIMPLE BAR DISPLAY WITH ALARM FLASHER . Schematic: Return to Display Circuits. By using two switching transistors and two LEDs, this circuit can distinguish low-level ac and dc signals. If the red LED illuminates, the signal is positive dc. If the yellow LED lights, the signal is negative dc. If the signal is ac, both LEDs will light. Bar Display With Alarm Flasher Circuit Schematic

Most of the power supply failure indicator circuits need a separate power-supply for them-selves. But the alarm circuit presented here needs no additional supply source. It employs an electrolytic capacitor to store adequate charge, to feed power to the alarm circuit which sounds an alarm for a reasonable duration when the mains supply fails. During the presence of mains power supply, the rectified mains voltage is stepped down to a required low level. Circuit diagram : Power Supply Failure Alarm Circuit Diagram A zener is used to limit the filtered voltage to 15-volt level. Mains presence is indicated by an LED. The low-level DC is used for charging capacitor C3 and reverse biasing switching transistor T1. Thus, transistor T1 remains cut-off as long as the mains supply is present. As soon as the mains power fails, the charge stored in the capacitor acts as a power-supply source for transistor T1. Since, in the absence of mains supply, the base of transistor is pulled ‘low’ via re...

Alternative version of the popular circuit, 3V battery supply - Still operating at 1.3V The main purpose of this design was to obviate a small defect of the very popular Fridge Door Alarm circuit, available on this website since 1999 and built by a lot of hobbyists. Unfortunately, that circuit stops operating when the battery voltage falls below about 2.6 - 2.7 Volts. This is due to the 4060 CMos IC used. In some cases, devices made by some manufacturers (but not Motorola's) fail to operate even at nominal 3V supply voltage. A simple cure to this shortcoming could be the substitution of the original IC specified with a 74HC4060 chip: this should allow circuit operation down to 2V but, unfortunately, this IC is not easy to locate. For this reason, an equivalent circuit using about the same parts counting was developed, in order to allow safe operation even when battery voltage falls down to about 1.3V. Circuit operation: The circuit, enclosed in a small box, should be placed in the ...

This long-range cordless burglar alarm circuit makes use of a cordless telephone (CLT) unit with paging facility and a few low-cost discrete components. The circuit is so simple that even a novice can easily construct it without any difficulty. When the ‘page’ button on a CLT is pressed and held in that position, the handset starts beeping to indicate that somebody is calling. This function is used here to build the gadget. The system consists of three sub-assemblies:      1. Wireless beeper. The handset of the CLT. 2. Infrared transmitter. A number of IR transmitter circuits based on the well-known 555 chip have been published earlier in EFY. Just select one circuit with a modulating frequency of 36 to 38 kHz and assemble it on a veroboard. After that, enclose it in a proper cabinet. (EFY note. A typical IR transmitter circuit used during testing is shown in Fig. 1.)   3. Infrared receiver-cum-control unit. The circuit diagram of this unit is shown in Fig. 2. Front end of this bloc...

Simple Mock Alarm with Call Bell Circuit Diagram is a fully automatic mock alarm to ward off any intruder to your house. The alarm becomes active at sunset and remains ‘on’ till morning. The flashing light-emitting diodes (LEDs) and beeps from the unit simulate the functioning of a sophisticated alarm system. Besides, the circuit turns on and off a lamp regularly at an interval of 30 minutes throughout the night. It also has a call bell facility. The circuit is built around CMOS IC CD4060B (IC1), which has an internal oscillator and a 14-stage binary divider to provide a long delay without using a high-value resistor and capacitor. Press switch S2 to provide 9V power supply to the circuit. During daytime, light-dependent resistor LDR1 offers little resistance and transistor T1 conducts. This drives transistor T2 into the cut-off mode, as its base is pulled to ground via transistor T1. Reset pin 12 of IC1 remains high as long as transistor T2 is cut off. This keeps the oscillator of IC...