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Simple Water Alarm Circuit Schematic .The LM1830 fluid detector IC from National Semiconduc tor is designed to be able to detect the presence of fluids using a probe. This chip requires a relatively high supply voltage and is not the most frugal power consumer. It is also quite specialised so unless you are buying in bulk the one-off price is not cheap.  An alternative circuit show n her e uses a standard CMOS IC type 74HC14. It has the advantage of operating with a 3 V supply and consumes less than 1 µA when the alarm is not sounding, this makes it ideal for use with batteries.  Water Alarm Schematic Circuit Diagram The 74HC14 has six inverters with hysteresis on their input switching thresholds. A capacitor (C1) and a feedback resistor (R1) is all that’s necessary to make an inverter into a square wave signal generator.  In the water alarm circuit the feedback resistor consists of R1 and the water sensor in series. R1 prevents any possibility of short-circuit between t...

Fire alarm can be made with a light sensor (LDR) as in the article with the title of Fire Alarm with this LDR sensor. Principles of fire detection Fire Alarm with LDR sensor is to detect the presence of smoke through the LDR. LDR in the series Fire Alarm does not stand alone in detecting a fire, but the LDR in the pair with the light shining on the LDR. Hence, in the detected smoke from the fire then the intensity of light received by the LDR LDR decreases and eventually trigger an alarm system on a series of Fire Alarm with this LDR sensor. Part 2 that in the series of Fire Alarm with Sensor LDR are some of the sensors, tone generator, audio power. Image Series Fire Alarm with Sensor LDR Function Section of the Fire Alarm with Sensor LDR Part of LDR and light sensor facing to fire smoke detection Part trigger using transistors and regulators as a trigger tone generator 7805 Tone generator section with IC UM66 Power audio section uses an audio power IC TDA 2002 which is equipped with v...

This is a simple Motorcycle Alarm With Transistor Circuit Diagram . It's designed to work at 12-volts. But - if you change the relay for one with a 6-volt coil - it'll protect your "Classic Bike". The standby current is virtually zero - so it won't drain your battery. Motorcycle Alarm With Transistor Circuit Diagram Any number of normally-open switches may be used. Fit the mercury switches so that they 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. While at least one switch remains closed - the siren will sound. About one minute after all of the switches have been opened again - the alarm will reset. How long it takes to switch off depends on the characteristics of the actual parts you've used. You can adjust the time to suit your requirements by changing the value of C1 and/or R3. The circuit is designed to use ...

Detects if a device is not properly connected to its supply Suitable for battery chargers, portable appliance supplies etc. 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. Circuit diagram: Broken...

Here is an ultra-sensitive LPG sensor that generates loud beeps when it senses any gas leakage. It detects vapours of liquefied petroleum gas anywhere between 200 and 10,000 ppm and drives a piezobuzzer to catch attention for immediate action. The buzzer beeps until the concentration of gas in the air decreases to a safe level. The circuit uses an MQ6 gas sensor, which is designed to sense LPG, propane and isobutane gases. Circuit and working Fig. 1 shows the circuit of the LPG sensor. The circuit is built around 5V voltage regulator 7805 (IC1), gas sensor MQ6 (GS1), counter IC 4060 (IC2) and a few discrete components. GS1 is a six-pin gas sensor that can detect very small traces of LPG in the air and has a swift response time. However, it has very less sensitivity to alcohol and smoke. The sensor’s output is in the form of resistance. Fig. 1: Circuit of the sensitive LPG sensor As indicated in Fig. 1, the pins of GSI are H, A and B, two each on either side. H pins are for the heater w...

If your PC overheats, it could damage its expensive components. Here’s a circuit that warns you of your PC getting heated. Today’s computers contain most of the circuitry on just a few chips and reduced power consumption is a byproduct of this LSI and VSLI approach. Some PCs still have power supplies that are capable of supplying around 200W, but few PCs actually consume power to this extent. On the other hand, apart from some portable and small desktop computers that use the latest micro-power components, most PCs still consume significant amount of power and generate certain amount of heat.  The temperature inside the aver-age PC starts to rise well above the ambient temperature soon after it is switched on. Some of the larger integrated circuits become quite hot and if the temperature inside the PC rises too high, these devices may not be able to dissipate heat fast enough. This, in turn, could lead to failure of devices and eventually of the PC.  Various means to combat overheati...

In this electronic circuit project Open door alarm a very simple 555 timer Open door alarm circuit project can be designed using an linear hall effect device like in this circuit diagram. This 555 timer Open door alarm circuit is based on the TL3103 linear Hall Effect device used for detecting the angle of rotation. The TL3103s are centered in the gap of a U-shaped permanent magnet. Open Door Alarm with 555 Timer Circuit Diagram: This type of circuit can sense the opening of a refrigerator door. When the door opens, a triac could be activated to control the inside light. The figure shows a door position alarm. When the door is opened, an LED turns on and the piezo alarm sounds for approximately 5 seconds. This door alarm electronic circuit uses a TL3019 Hall Effect device for the door sensor. This normally open switch is located in the door frame. The magnet is mounted in the door. When the door is in the closed position, the TL3019 output goes to logic low, and remains low until the d...

This is a complete alarm system with 5 independent zone ssuitable for a small office or home environment. It uses just 3CM IC`s and features a timed entry / exit zone, 4 immediate zones and a panic button. There are indicators for each zone a“system armed” indicator. The schematic is as follows: 5 Zone alarm Circuit Diagram Circuit Notes: Each zone uses a normally closed contact. These can be micro switches or standard alarm contacts (usually reed switches).Suitable switches can be bought from alarm shops and concealed indoor frames, or window ledges.Zone 1 is a timed zone which must be used as the entry andexit point of the building. Zones 2 – 5 are immediate zones,which will trigger the alarm with no delay. Some RF immunity isprovided for long wiring runs by the input capacitors, C1-C5. C7and R14 also form a transient suppresser. The key switch acts asthe Set/Unset and Reset switch. For good security thisshould be the metal type with a key. Operation: At switch on, C6 will charge via...

Are you having a hard time waking your hubby from sleeping? And when you leave the house for work, are you in doubt that he has not gotten out of bed? One thing that will stop your worries is to use this clock that does not just tell time but also “swears”. This is an All-in-one alarm clock. It shows an alphanumeric character, it has a calendar, temperature, and a light sensor to control its brightness. You can plug it on to your power source or use a battery. Although this is cool, It’s not ok being around kids. We don’t want young kids to learn to swear or say bad things, right?   [ ]

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.   Sourced by Part Total Qty. Description Substitutions C1 1 0.01uF Ceramic Disc Capacitor C2 1 100uF 35V Electrolytic Capacitor R1 1 1K 1/4W Resistor R2 1 10K 1/4W Resistor R3 1 15K 1/4W Resistor R4 1 470 Ohm 1/4W Resistor D1, D3, D4 3 1N4004 Rectifier Diode D2 1 Red LED U1 1 555 Timer IC K1 1 SPST 12V Automotive Relay ...

Presented here is a simple locker security alarm that can be used to protect a locker from unauthorised access. The circuit is low-cost and forms a fool-proof alarm that receives its control signal from a standard reed switch. The circuit works off a 12V DC power supply. Fig. 1: Circuit diagram of the locker-security alarm Fig. 2: An actual-size, single-side PCB of the locker- security alarm    Fig. 3: Component layout for the PCB Circuit and working Fig. 1 shows the circuit diagram of the locker-security alarm. The circuit is built around quad NOR gate IC CD4001 (IC1), reed switch RS1 and transistor BC547 (T1). reed switch RS1, together with a permanent magnet, forms the sensing unit as shown in Fig. 1. The magnet is fixed on the door of the locker and reed switch RS1 on the door-frame such that when the door closes, both of them come close to each other. Now, when switch S1 is turned on, 12V supply is extended to the circuit. Normally, when the locker is closed, the reed swi...

When SI (sensor) is closed, power is applied to U2, a dual timer. After a time determined by C2, CI is energized after a predetermined time determined by the value of C5, pin 9 of U2 becomes low, switching off the transistor in the optoisolater, cutting anode current of SCR1 and de-energizing Kl. The system is now reset. Notice that (i6x C2) is less than (R7xC$). The ON time is approximately given by:(R7xC5)-(R6xC2) = Ton  Burglar Alarm With Timed Shutoff Circuit Diagram

Description The Basic Alarm Circuit has an automatic Exit/Entry Zone - an Instant Alarm Zone that will accept both normally-closed and normally-open triggering devices - and an "Always On" 24-hour Personal Attack/Tamper Zone. By using the Expansion Modules - you can add as many extra alarm zones as you require. Schematic Diagram The Alarm is armed and disarmed by SW1. Before you move the switch to the "set" position - all the green LEDs should be lighting. You then have up to about a minute to leave the building. As you do so - the Buzzer will sound. It should stop sounding when you close the door behind you. This indicates that the Exit/Entry loop has been successfully restored within the time allowed.  When you re-enter the building - you have up to about a minute to move SW1 to the "off" position. If SW1 is not switched off in time - the relay will energize - and the main bell will ring. It will continue ringing for up to about 40 minutes. But it can...

Reagarding this circuit sent out an alarm when its LDR sensor is exposed to light by sun or lamp. A 555 astable multivibrator was used here which sent signal a tone of about 1kHz upon detecting light. The sensor when exposed by light completes the circuit and makes the 555 oscillate at about 1kHz with transistor to drive current. The sensor is also shown in the circuit diagram. It has to placed making an angle of about 30 – 45 degrees to the ground.  Sensitivity can be adjust with P1.  This makes the sun light to flow through it to the ground and prevents the alarm from going on due to the stored light on the sensor.

The Travel Touch Alarm can be used to provide a audible alarm  when someone touches the door knob or handle of your hotel room. The door knob or handle must be made of metal for the circuit to work. The main chip in the circuit is a 555 timer which will be triggered if a hand comes close to or touches the door knob. 555 Timer Travel Touch Alarm Circuit Diagram The circuit attaches to the door knob at the end of the 1 meg ohm resistor. Once the timer is triggered the LED will light and the UJT will output a tone to the speaker. The timer will time out in 5 seconds. The sensitivity of the trigger can be changed by changing the 1 meg ohm resistor to another value. The 5 second time out can be adjusted by changing the value of the resistor connected between pin 8 and pin 7. The output tone can be changed by changing the RC values on the base of the UJT.

This Simple Emergency Light and Alarm Circuit Diagram is permanently plugged into a mains socket andNI-CD batteries are trickle-charged. When a power outage occurs,the lamp automatically illuminates. Instead of illuminating alamp, an alarm sounder can be chosen.When power supply is restored, the lamp or the alarm isswitched-off. A switch provides a “latch-up” function, in orderto extend lamp or alarm operation even when power is restored.Circuit operation:Mains voltage is reduced to about 12V DC at C2`s terminals, bymeans of the reactance of C1 and the diode bridge (D1-D4). Thusavoids the use of a mains transformer.   Simple Emergency Light and Alarm Circuit Diagram Trickle-charging current for the battery B1 is provided by theseries resistor R3, D5 and the green LED D6 that also monitorsthe presence of mains supply and correct battery charging.Q2 & Q3 form a self-latching pair that start operatingwhen a power outage occurs. In this case, Q1 biasing becomespositive, so this tr...

This is the Simple Miniature Loop Alarm Circuit Diagram. The simple construction, reliable operation, very small power consumption, and, most of all, small size. I started with CMOS logic gates, but was soon forced to abandon the concept after a few unsuccessful (and far too complicated) attempts. Then I suddenly realized that a simple transistor switch might do the job and I was right. Simple Miniature Loop Alarm Circuit Diagram Notes As you can clearly see from the schematics, the circuit is utterly primitive and consists of two identical transistor switches. Each has its own alarm LED and they're coupled to a neat 82dB buzzer. The two 1N4148 diodes are used to prevent a signal from one sensor from triggering both LEDs. The sensors used are either wire loops or normally closed reed switches or even a combination of both. You could, for example, tie a wire loop to your suitcase and place a reed switch to the door of your hotel room.Since this little alarm is intended to be kept in...

This electronic circuit project of Miniature Loop Alarm. As you can clearly see from the schematics, the circuit is utterly primitive and consists of two identical transistor switches. Each has its own alarm LED and they're coupled to a neat 82dB buzzer. The two 1N4148 diodes are used to prevent a signal from one sensor from triggering both LEDs. The sensors used are either wire loops or normally closed reed switches or even a combination of both. You could, for example, tie a wire loop to your suitcase and place a reed switch to the door of your hotel room. Miniature Loop Alarm Circuit Diagram: Since this little alarm is intended to be kept in arms reach at all times, there aren't any provisions for automatic shutdown after a certain period of time. The buzzer will sound until you turn the whole circuit off or connect the wire loop back to the jumpers. The same goes for the two LEDs, each indicating its own zone. Construction is not critical and there aren't any traps for ...

This Simple 5 Digit Alarm Control keypad Circuit Diagram switch will suit the Modular Burglar Alarm circuit.However, it also has other applications. The Keypad must be the kind with a common terminal and a separate connection for each key. On a 12-key pad, look for 13 terminals. The matrix type with7 terminals will NOT do. Choose the five keys you want as your code, and connect them to `A, B, C, D & E`. 5 Digit Alarm Control keypad Circuit Diagram Wire the common to R1 and all the remaining keys to `F`. Because your choice can include the non-numeric symbols, almost 100 000different codes are available. The Alarm is set using the first four of your five chosen keys. When `A, B, C & D` are press edin the right order and within the time set by C1 and R2 (about10 seconds), current through R11 switches Q6 on. The relay energizes, and then holds itself on by providing base current forQ6 through R12. The 12-volt output switches from the “off” to the “set ” terminal, and the LED lig...