Supreem Circuits Diagram and Projects: Alarm and Security

Build a Simple Emergency Light and Alarm Circuit Diagram

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This <b>Simple Emergency Light and Alarm Circuit Diagram</b> 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.</div>
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 <b>Simple Emergency Light and Alarm Circuit Diagram</b></div>
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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 transistor turns on the self latching pair.</div>
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If SW3 is set as shown in the circuit diagram, the lampilluminates via SW2, which is normally closed; if set the otherway, a square wave audio frequency generator formed by Q4, Q5 andrelated components is activated, driving the loudspeaker.If SW1 is left open, when mains supply is restored the lamp orthe alarm continue to operate. They can be disabled by openingthe main on-off switch SW2.If SW1 is closed, restoration of the mains supply terminateslamp or alarm operation, by applying a positive bias to the Baseof Q2.</div>
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<b>Notes:</b></div>
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Close SW2 after the circuit is plugged.Warning! The circuit is connected to 220Vac 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.  </div>
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<b>Parts List</b><br />
R1____________220K 1/4W Resistor<br />
R2____________470R 1/2W Resistor<br />
R3____________390R 1/4W Resistor<br />
R4______________1K5 1/4W Resistor<br />
R5______________1R 1/4W Resistor<br />
R6_____________10K 1/4W Resistor<br />
R7____________330K 1/4W Resistor<br />
R8____________470R 1/4W Resistor<br />
R9____________100R 1/4W Resistor<br />
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C1____________330nF 400V Polyester Capacitor<br />
C2_____________10΅F 63V Electrolytic Capacitor<br />
C3____________100nF 63V Polyester Capacitor<br />
C4_____________10nF 63V Polyester Capacitor<br />
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D1-D5________1N4007 1000V 1A Diodes<br />
D6______________LED Green (any shape)<br />
D7___________1N4148 75V 150mA Diode<br />
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Q1,Q3,Q4______BC547 45V 100mA NPN Transistors<br />
Q2,Q5_________BC327 45V 800mA PNP Transistors<br />
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SW1,SW2________SPST Switches<br />
SW3____________SPDT Switch<br />
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LP1____________2.2V or 2.5V 250-300mA Torch Lamp<br />
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SPKR___________8 Ohm Loudspeaker<br />
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B1_____________2.5V Battery (tw1o AA NI-CD rechargeable cells wired in series)<br />
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PL1____________Male Mains plug<br />
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Build a Simple Emergency Light and Alarm Circuit Diagram

This Simple Emergency Light and Alarm Circuit Diagram is permanently plugged into a mains socket andNI-CD batteries are trickle-charged. ...

Build a PIC Security System Dials Your Cell Phone Circuit Diagram

Alarm and Security 03:46

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This is a simple <b>PIC Security System Dials Your Cell Phone Circuit Diagram</b>. Do-it-yourself phone dialer security system calls your cell phone, office etc. whenever a door or window is opened, or panic button is pressed. Great Home Alarm.<br />
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<b>PIC Security System Dials Your Cell Phone Circuit Diagram</b><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh_G-428wJnAjO0BOLRrOfzGkdiozvfDAOIDyO9Cmcl6-qgzPv283R61ZruBJHOvV2vCknswTzGR1ovcsa1efYkVde4a1BuxLVnqxN_YuP4qu55nTaYBeJGOCn9DVoQjSR6Y7YrLAE1xk5Z/s1600/PIC+Security+System+Dials+Your+Cell+Phone+Circuit+Diagram.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img alt="PIC Security System Dials Your Cell Phone Circuit Diagram" border="0" height="185" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh_G-428wJnAjO0BOLRrOfzGkdiozvfDAOIDyO9Cmcl6-qgzPv283R61ZruBJHOvV2vCknswTzGR1ovcsa1efYkVde4a1BuxLVnqxN_YuP4qu55nTaYBeJGOCn9DVoQjSR6Y7YrLAE1xk5Z/s400/PIC+Security+System+Dials+Your+Cell+Phone+Circuit+Diagram.gif" title="PIC Security System Dials Your Cell Phone Circuit Diagram" width="400" /></a></div>
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The circuit consists of a small PIC microcontroller, assembly program, and a few other parts to detect a switch closure from an open door, window, or manual push button and then dial the cell phone number, and transmit a steady tone to indicate the source of the call. The circuit uses the pulse dialing system to interrupt the line connection a number of times to indicate each digit. Pulse dialing (the oldest form of dialing) works by actually disconnecting or "hanging up" the phone line a number of times to indicate each digit. For example, the digit "5" would be dialed by disconnecting and reconnecting the line 5 times in short intervals of about 100mS. There is about a 1 second pause (with the line connected) between each digit. The timing is not critical and I was able to dial 411 and connect to the local information service just using a momentary push button switch in series with the phone line.</div>
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<b>Circuit Operation:</b><br />
In operation, the switch closure is detected on pin 7 of the processor which activates the reed relay and takes the line off-hook for 3 seconds to establish the dial tone. The processor then dials the number by opening and closing the relay a number of times for each digit. When dialing is complete, the processor waits 3 seconds and then transmits a steady tone of about 300Hz for 30 seconds through the modem transformer. The call is then terminated and the processor waits for the switch to open before resetting.<br />
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<b>Design Considerations:</b><br />
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The PIC16F628 (18 pin) processor was selected because I had a few on hand and my homemade hardware programmer only accepts 18 pin devices. A smaller 8 pin device could have been used since only three I/O lines are needed, but the difference in cost is only about $1.50. One of the I/O lines (RA5) is used for programming and is always an input, but can used as a functional input so the switch closure could be detected on this line thus eliminating the need for one pullup resistor. But I elected to use 3 consecutive I/O pins (7,8,9) of the 8 bit port B and leave RA5 pulled up with a extra 10K resistor.<br />
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The output pins (8,9) that drive the relay and transformer are limited to 25mA of current each, so an extra transistor (2N2222A) was needed to supply additional current to the relay coil. The transformer resistance is around 100 ohms, so an additional 330 ohm resistor was added in series with pin 9 to limit the transformer current to around 10mA. An LED indicator and 330 ohm resistor were used on pin 8 to observe the dialing activity and indicate the line status. Several of the parts (relay, transformer and blocking capacitor) were obtained from an old 56K modem card.<br />
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The schematic shows a 47uF / 50 volt non-polarized capacitor used to block DC current to the transformer, however a regular polarized 50uF cap could be used if correct phone line polarity is observed. The modem was probably designed to work with unknown polarities at different locations, so a non-polarized cap was used. It's possible the cap and 470 ohm resistor can be replaced with a single resistor in series with the line to set the "off hook" line current to around 20mA. This may cause partial saturation of the transformer and reduced audio level, but might work well enough.<br />
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The power supply voltage is not critical and a 4.5 volt supply from three AA batteries should work. Or a switching type regulated 5 volt wall transformer can be used. The problem is insuring the relay gets enough voltage to operate. The rest of the circuit should run on reduced voltage. I used a 4.2 volt cell phone charger that worked well.<br />
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Build a PIC Security System Dials Your Cell Phone Circuit Diagram

This is a simple PIC Security System Dials Your Cell Phone Circuit Diagram . Do-it-yourself phone dialer security system calls your cell p...

Build a 5 Zone alarm Circuit Diagram

Alarm and Security 06:12

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This is a complete alarm system with 5 independent zonessuitable for a small office or home environment. It uses just 3CM IC`s and features a timed entry / exit zone, 4 immediatezones and a panic button. There are indicators for each zone a“system armed” indicator. The schematic is as follows:</div>
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<b>5 Zone alarm Circuit Diagram</b></div>
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<b>Circuit Notes:</b></div>
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Each zone uses a normally closed contact. These can be microswitches 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.</div>
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<b>Operation:</b></div>
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At switch on, C6 will charge via R11, this acts as the exitdelay and is set to around 30 seconds. This can be altered byvarying either C6 or R11. Once the timing period has elapsed,LED6 will light, meaning the system is armed. LED6 may be mountedexternally (at the bell box for example) and providesvisual indication that the system has set. Once set any contactthat opens will trigger the alarm, including Zone 1. To preventtriggering the alarm on entry to the building, the concealedre-entry switch must be operated. This will discharge C6 andstart the entry timer. The re-entry switch could be a concealedreed switch, located anywhere in a door frame, but invisibleto the eye. The panic switch, when pressed, will trigger thealarm when set. Relay contacts RLA1 provide the latch, RLA2operate the siren or buzzer.</div>
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Build a 5 Zone alarm Circuit Diagram

This is a complete alarm system with 5 independent zonessuitable for a small office or home environment. It uses just 3CM IC`s and feature...

Simple Cmos Motorcycle Alarm Circuit Diagram

Alarm and Security 02:15

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This Simple<b> Cmos Motorcycle Alarm Circuit Diagram</b> 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.<br />
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Cmos Motorcycle Alarm Schematic Diagram</h2>
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<b>Notes</b></div>
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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.</div>
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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.</div>
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While at least one switch remains closed the siren will sound. About  thirty seconds after all of the switches have been opened, the alarm  will reset. How long it takes to switch off depends on the  characteristics of the actual components used. You can adjust the time  to suit your requirements by changing the value of R6 and/or C4.</div>
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The circuit is designed to use an electronic Siren drawing 300 to  400mA. It's not usually a good idea to use the bike's own Horn because  it can be easily located and disconnected. However, if you choose to use  the Horn, remember that the alarm relay is too small to carry the  necessary current. Connect the coil of a suitably rated relay to the  "Siren" output. This can then be used to sound the Horn - flash the  lights etc.</div>
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The circuit board and switches must be protected from the elements.  Dampness or condensation will cause malfunction. Connect the 1-amp  in-line fuse AS CLOSE AS POSSIBLE to your power source. This is VERY  IMPORTANT. The fuse is there to protect the wiring - not the alarm.  Exactly how the system is fitted will depend on the make of your  particular machine - so I'm unable to provide any further help or advice  in this regard.</div>
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The quiescent (standby) current of the circuit is virtually zero - so  there is no drain on the battery. If you want to operate the alarm  manually use a key-switch or a hidden switch connected to the "off/set"  terminals. For automatic operation connect a wire from the ignition  circuit to the "ignit" terminal. Then every time you turn-off the  ignition - the alarm will set itself. Remember that this wire from the  ignition switch is not protected by your 1-amp inline fuse. So unless  its run is very short - fit the wire with its own 1-amp fuse as close as  possible to its source.</div>
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When you set the alarm - if one of the switches is closed - the siren  will sound. This could cause annoyance late at night. A small  modification will allow you to Monitor The State Of The Switches using  LEDs. When the LEDs are all off - the switches are all open - and it's  safe to turn the alarm on.</div>
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Veroboard Layout</h2>
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Simple Cmos Motorcycle Alarm Circuit Diagram

This Simple Cmos Motorcycle Alarm Circuit Diagram features an intermittent siren output and automatic reset. It can be operated manuall...

Build an Alarm Control Keypad Circuit Diagram

Alarm and Security 06:26

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The IC is a quad 2 input “AND” gate, a CMOS 4081. These gatesonly produce a HIGH output, when BOTH the inputs are HIGH. Whenthe key wired to `E` is pressed, current through R1 and D1switches Q5 on. The relay energises; and Q5 is `latched on` byR8. Thus, the Alarm is set by pressing a single key, say one ofthe tw1o non-numeric symbols.The alarm will switch off when the 4 keys connected to“A,B,C,D” are pushed in the right order. The circuit worksbecause each gate `Stands` upon its predecessor.If any key otherthan the correct key is pushed, then gate 1 is knocked out of thestack, and the code entry fails. </div>
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Pin 1 is held high by R4. This`Enables` gate 1; and when button `A` is pressed, theoutput at pin 3 will go high. This output does tw1o jobs.It locksitself `ON` through R2 and it `Enables` gate 2, by taking pin 5,high. Now, if `B` is pressed, the output of gate 2, at pin 4will go high. This output does tw1o jobs. It locks itself `ON`through R3 and it `Enables` gate 3 by taking pin 12 high.Now, if `C` is pressed, the output of gate 3 will lock itself`ON` through R5 and, by taking pin 8 high, `Enable` gate 4.Pressing `D` causes gate 4 to do the same thing; only this timeits output, at pin 10, turns Q4 `ON`. </div>
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This takes the base of Q5to ground, switching it off and letting the relay drop out. Thisswitches the alarm off.Any keys not connected to `A B C D E` are wired to the base ofQ1. Whenever `E` or one of these other keys is pressed, pin 1 istaken low and the circuit is reset. In addition, if `C` or `D`is pressed out of sequence, then Q2 or Q3 will take pin 1 low andthe circuit will reset. Thus nothing happens until `A` ispressed. Then if any key other than `B` is pressed, the circuitwill reset.Similarly, after `B`, if any key other than `C` is pressed,the circuit will reset. The same reasoning also applies to `D`.The Keypad needs to be the kind with a common terminal and aseparate connection to each key. On a 12 key pad, look for 13terminals. The matrix type with 7 terminals will NOT do. </div>
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Wire thecommon to R1 and your chosen code to `A B C D`. Wire `E` to thekey you want to use to switch the alarm on. All the rest go tothe base of Q1.The diagram should give you a rough guide to the layout of thecomponents, if you are using a strip board. The code you choosecan include the non-numeric symbols. In fact, you do not have touse a numeric keypad at all, or you could make your own keypad.I haven`t calculated the number of combinations of codesavailable, but it should be in excess of 10 000 with a 12 keypad; and, after all, any potential intruder will be ignorant ofthe circuit`s limitations. Of Course, if you must have a moresecure code, I can think of no reason why you shouldn`t addanother 4081 and continue the process of enabling subsequentgates. Or you could simply use a bigger keypad with more “WRONG”keys.Any small audio transistors should do. </div>
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The 27k resistors couldbe replaced with values up to 100k. And the only requirementsfor the 4k7 resistors is that they protect the junctions whileproviding enough current to turn the transistors fully on.Capacitors (C1 C2 C3 C4 C5) are there to slow response timeand overcome any contact bounce. They are probably unnecessary.</div>
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Alarm Control Keypad Circuit Diagram</div>
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Build an Alarm Control Keypad Circuit Diagram

The IC is a quad 2 input “AND” gate, a CMOS 4081. These gatesonly produce a HIGH output, when BOTH the inputs are HIGH. Whenthe key wired ...

Burglar Alarm With Timed Shutoff Circuit Diagram

Alarm and Security 06:46

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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 </div>
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<b>Burglar Alarm With Timed Shutoff Circuit Diagram</b></div>
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Burglar Alarm With Timed Shutoff Circuit Diagram

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 tim...

555-IC Timed Beeper Circuit Diagram

555, Alarm and Security 02:05

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This is a simple t<b>imed beeper circuit diagram</b> of beeper using 555 timer. This circuit can be  employed to energize lights, horn, or other signaling device at any  desired interval when the mercury switch is triggered. Since the current  handling capability of mercury switch is not so high, an SCR is used to  handle current drawn by the <b>555 timer circuit</b>. Chose the SCR  current  rating of 500mA at minimum to safely drive the 555 IC and the relay. The  relay is not needed when the current drawn by alarm is less than 200mA,  in this case the alarm can be installed to directly replace the relay  coil.  Here is the schematic diagram of the circuit.</div>
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<b>555-IC Timed Beeper Circuit Diagram</b><br />
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555-IC Timed Beeper Circuit Diagram

This is a simple t imed beeper circuit diagram of beeper using 555 timer. This circuit can be employed to energize lights, horn, or othe...

Simple Luggage Security Alarm Schematic

Alarm and Security 05:42

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We usually lock our luggage utilizing a chain-and-lock arrangement when  in travelling by a train of bus. But, still we are worried, apprehending  that someone may possibly break the chain and steal our luggage. The  following schematic is really a very simple and easy build luggage  security alarm circuit to alert you when a person tries to break the  chain.</div>
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Transistor T1 allows supply to the sound generator chip when the base  current begins flowing through it. When the wire (thin enameled copper  wire of 30 to 40 SWG, applied for winding transformers) loop around the  chain is cracked by someone, the base of transistor T1, which was  previously linked with positive rail, becomes opened. Because of this,  transistor T1 gets forward biased to extend the positive power source  towards the alarm circuit. <a href="http://www.circuitsproject.com/" target="_blank">Link</a><br />
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In idle mode, the power source  consumption within the circuit is lowest and as a result, it could  possibly be utilized for numerous travel hrs.<br />
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To make it possible  for generation of various alarm sounds, joints to pin 1 and 6 could be  designed as shown in the following table:<br />
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Simple Luggage Security Alarm Schematic

We usually lock our luggage utilizing a chain-and-lock arrangement when in travelling by a train of bus. But, still we are worried, appre...

2 Transistor Electronic Siren Circuit Diagram

Alarm and Security 10:07

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This is the <b>electronic siren schematic diagram</b> which used 2 transistor  BC547 and BC557. The siren is powered by 9V battery or power supply  adapter and use 8 ohm speaker to produce the sound. The <b>siren</b> is  controlled by the touch plate switch. If you touch the plate, then this  electronic siren will be activated. </div>
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<b>2 Transistor Electronic Siren Circuit Diagram</b></div>
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2 Transistor Electronic Siren Circuit Diagram

This is the electronic siren schematic diagram which used 2 transistor BC547 and BC557. The siren is powered by 9V battery or power supp...

Build a Rain and Water Alarm Circuit Diagram

Alarm and Security 04:08

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This is the<b> circuit diagram</b> of <b>Rain and Water Alarm circuit</b>. This circuit  generates alarm sound when its sensor is witted by water which make a  short circuit (connection) between X and Y. A tone of about 1kHz which  can be hear while detecting water, is provided by a stable multivariate from timer IC 555.</div>
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The sensor when witted by  water completes the circuit and causes the 555 oscillate at about 1kHz.  It has to placed generating an angle of about 30 – 45 degrees to the  ground. This tends to make the rain water to flow over it towards the  ground and prevents the alarm from going on because of the stored water  on top of the sensor.</div>
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The metal implemented for making the sensor  is required to be aluminum and not copper. This is simply because  copper forms a blue oxide on its layer on prolonged exposure to moisture  and needs to be cleaned on a regular basis.The aluminum foils may be  secured to the wooden / plastic board via epoxy adhesive or small  screws. The connection between X and Y from the sensor may be obtained  by small crocodile clips or you could possibly use screws.</div>
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<b> Build a Rain and Water Alarm Circuit Diagram</b><br />
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 <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDsoQeoz9evAn7PsmibZFMEHfdsG9VRZRYMA5NzM8QRPyu-bxu4q-VcOoO41sZImF0xjrg66lCFdtkaBCTz51T3M9s8s8czLT3XmpvvZHsoOyIJ7_7ePCBkpL6ZTkbenRLi9A8emC7OcW3/s1600/Rain++Water+Alarm+Circuit.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img alt="Build a Rain and Water Alarm Circuit Diagram" border="0" height="351" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDsoQeoz9evAn7PsmibZFMEHfdsG9VRZRYMA5NzM8QRPyu-bxu4q-VcOoO41sZImF0xjrg66lCFdtkaBCTz51T3M9s8s8czLT3XmpvvZHsoOyIJ7_7ePCBkpL6ZTkbenRLi9A8emC7OcW3/s400/Rain++Water+Alarm+Circuit.jpg" title="Build a Rain and Water Alarm Circuit Diagram" width="400" /></a></div>
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Build a Rain and Water Alarm Circuit Diagram

This is the circuit diagram of Rain and Water Alarm circuit . This circuit generates alarm sound when its sensor is witted by water whi...

Simple Electronic Siren Schematic Diagram

Alarm and Security 03:14

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This is the <b>simple electronic siren schematic</b>, built using three ICs: CD4011  NAND gate logic, CD4066 Bilateral Switch and CD4046 Micro power  Phase-Locked Loop (PLL). Itis quite <b>simple electronic siren</b> design, low  cost and easy to assemble.</div>
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With this circuit we can create a  changing tone siren. The oscillator IC1A-B consists of two NAND gates  logic, oscillating at very low frequency. The oscillation leads the IC2,  which is an electronic bilateral switch, which opens and closes in the  rate of oscillation. When the switch is closed then the voltage charging  the capacitor C3 through the resistor R2. When the switch opens the IC2  C3 discharge through the R3. </div>
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The voltage which is charged by C3  regulates the VCO IC3 which is a PLL, so that we have at the output of a  changing sound. You can experiment with the values ??of resistors and  capacitors to change the sound of the siren. The R1, C1 time control  function, the R3, C3 control the change of sound and the R4, C2 control  the frequency of sound produced. </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi5YKF6Ig_1ZvQ_yiYYoGWt9kss26u7oAh3i4XbDjXfMMcMzoj0_L461KhSfSwx9FJ64vfUh4cNdXVLXWnvug95gD_qjUsmTf8kkJl8j2IRaz7h_jPQ34N2s0GTBEafQiqynzb_D-rGMtTA/s1600/sirn.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img alt="Simple Electronic Siren Schematic Diagram" border="0" height="210" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi5YKF6Ig_1ZvQ_yiYYoGWt9kss26u7oAh3i4XbDjXfMMcMzoj0_L461KhSfSwx9FJ64vfUh4cNdXVLXWnvug95gD_qjUsmTf8kkJl8j2IRaz7h_jPQ34N2s0GTBEafQiqynzb_D-rGMtTA/s400/sirn.png" title="Simple Electronic Siren Schematic Diagram" width="400" /></a></div>
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Simple Electronic Siren Schematic Diagram

This is the simple electronic siren schematic , built using three ICs: CD4011 NAND gate logic, CD4066 Bilateral Switch and CD4046 Micro p...

Refrigerator Door Alarm

Alarm and Security 07:11

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Do your kids leave the door to the refrigerator open? Or does your  celery reach out to keep the door from closing properly when you turn  your back? Here's a simple circuit that beeps whenever the door is open  for an extended period of time (which will also put a little pressure on  the fridge loiterers in the house).<br />
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<b><span style="font-size: medium;">Simple Refrigerator Door Alarm Circuit Diagram </span></b><br />
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The photocell has a very high resistance in the dark which drops  very low when the door opens and the light turns on. The 22 uF capacitor  begins to charge and when the voltage reaches the zener voltage, the  beeper sounds. Closing the door allows the capacitor to discharge  through the 10 meg.  resistor, resetting the beeper. The circuit draws  very little power when the door is shut and only draws significant  current when the beeper is sounding. The transistor may be a single NPN  darlington such as the MPS-A14 or two 2N4401's connected as shown. Other  types will also work. The delay may be changed by changing the value of  the capacitor. It may be a good idea to add a 10 uF capacitor across  the battery.</div>
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Refrigerator Door Alarm

Do your kids leave the door to the refrigerator open? Or does your celery reach out to keep the door from closing properly when you turn ...

Simple Car Alarm Arming Horn Beep Canceller

Alarm and Security 01:55

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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. </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7Qc6zJtL7aHE55ofIghLXqYGkvTN-dufEtSxiNa4IzBFY9ksUJIBMJ1vsYUnBFSkN1Tz0LyY3FGIESjdrfFcoVYtpInQFGji4VfrgZddP0JWRucD8KPFWgdO8QNf-oIziYY2gg0ZJDyQy/s1600/beep+canceller.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img alt="Simple Car Alarm Arming Horn Beep Canceller" border="0" height="205" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7Qc6zJtL7aHE55ofIghLXqYGkvTN-dufEtSxiNa4IzBFY9ksUJIBMJ1vsYUnBFSkN1Tz0LyY3FGIESjdrfFcoVYtpInQFGji4VfrgZddP0JWRucD8KPFWgdO8QNf-oIziYY2gg0ZJDyQy/s400/beep+canceller.gif" title="Simple Car Alarm Arming Horn Beep Canceller" width="400" /></a></div>
 Sourced by <a href="http://www.aaroncake.net/circuits/beepcancel.asp" rel="nofollow" target="_blank">Link</a><br />
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<span style="color: white;"><b><span style="font-family: Arial;">Total Qty.</span></b></span></center>
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<span style="color: white;"><b><span style="font-family: Arial;">Description</span></b></span></center>
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<span style="color: white;"><b><span style="font-family: Arial;">Substitutions</span></b></span></center>
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<tr bgcolor="#072653"><td><span style="color: white;">C1</span></td><td><span style="color: white;">1</span></td><td><span style="color: white;">0.01uF Ceramic Disc Capacitor</span></td><td><span style="color: white;"><br /></span></td></tr>
<tr bgcolor="#072653"><td><span style="color: white;">C2</span></td><td><span style="color: white;">1</span></td><td><span style="color: white;">100uF 35V Electrolytic Capacitor</span></td><td><span style="color: white;"><br /></span></td></tr>
<tr bgcolor="#072653"><td><span style="color: white;">R1</span></td><td><span style="color: white;">1</span></td><td><span style="color: white;">1K 1/4W Resistor</span></td><td><span style="color: white;"><br /></span></td></tr>
<tr bgcolor="#072653"><td><span style="color: white;">R2</span></td><td><span style="color: white;">1</span></td><td><span style="color: white;">10K 1/4W Resistor</span></td><td><span style="color: white;"><br /></span></td></tr>
<tr bgcolor="#072653"><td><span style="color: white;">R3</span></td><td><span style="color: white;">1</span></td><td><span style="color: white;">15K 1/4W Resistor</span></td><td><span style="color: white;"><br /></span></td></tr>
<tr bgcolor="#072653"><td><span style="color: white;">R4</span></td><td><span style="color: white;">1</span></td><td><span style="color: white;">470 Ohm 1/4W Resistor</span></td><td><span style="color: white;"><br /></span></td></tr>
<tr bgcolor="#072653"><td><span style="color: white;">D1, D3, D4</span></td><td><span style="color: white;">3</span></td><td><span style="color: white;">1N4004 Rectifier Diode</span></td><td><span style="color: white;"><br /></span></td></tr>
<tr bgcolor="#072653"><td><span style="color: white;">D2</span></td><td><span style="color: white;">1</span></td><td><span style="color: white;">Red LED</span></td><td><span style="color: white;"><br /></span></td></tr>
<tr bgcolor="#072653"><td><span style="color: white;">U1</span></td><td><span style="color: white;">1</span></td><td><span style="color: white;">555 Timer IC</span></td><td><span style="color: white;"><br /></span></td></tr>
<tr bgcolor="#072653"><td><span style="color: white;">K1</span></td><td><span style="color: white;">1</span></td><td><span style="color: white;">SPST 12V Automotive Relay</span></td><td><span style="color: white;"><br /></span></td></tr>
<tr bgcolor="#072653"><td><span style="color: white;">MISC</span></td><td><span style="color: white;">1</span></td><td><span style="color: white;">Board, Wire, Socket For U1, Case</span></td><td><span style="color: white;"><br /></span></td></tr>
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Simple Car Alarm Arming Horn Beep Canceller

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 so...

VFD Talking Alarm Clock

Alarm and Security 06:22

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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”.<br />
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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?  </div>
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<a href="http://streampowers.blogspot.com/2012/08/vfd-talking-alarm-clock.html" target="_blank">Streampowers </a></div>
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VFD Talking Alarm Clock

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...

Build a Radio Wave Alarm

Alarm and Security 22:39

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This simple circuit is sure to have the police beating a path to your  door- however, it has the added advantage of alerting you to their  presence even before their footsteps fall on the doormat.<br />
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<b>Simple Radio Wave Alarm</b> <b>Circuit Diagram</b> :<br />
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<img alt="Build a Radio Wave Alarm" border="0" id="BLOGGER_PHOTO_ID_5787564196794800962" src="http://2.bp.blogspot.com/-uGN-46wwnuI/UFGO-SC5G0I/AAAAAAAAImU/3JEPSUAWq7k/s400/Simple%2BRadio%2BWave%2BAlarm-Circuit%2BDiagram.gif" style="height: 331px; width: 400px;" title="Build a Radio Wave Alarm" /></div>
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<b>Notes :</b></div>
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<li>The  circuit transmits on Medium Wave (this is the small problem with the  police). IC1a, together with a sensor (try a 20cm x 20cm sheet of tin  foil) oscillates at just over 1MHz. This is modulated by an audio  frequency (a continuous beep) produced by IC1b. When a hand or a foot  approaches the sensor, the frequency of the transmitter (IC1a) drops  appreciably.</li>
<li>Suppose now that the circuit transmits at 1MHz.  Suppose also that your radio is tuned to a frequency just below this.  The 1MHz transmission will therefore not be heard by the radio. But  bring a hand or a foot near to the sensor, and the transmitter's  frequency will drop, and a beep will be heard from the radio.</li>
<li>Attach  the antenna to a multiplug adapter that is plugged into the mains, and  you will find that the Medium Wave transmission radiates from every wire  in your house. Now place a suitably tuned Medium Wave radio near some  wires or a plug point in your house, and an early-warning system is set  up.</li>
<li>Instead of using the sheet of tin foil as the sensor, you  could use a doorknob, or burglar bars. Or you could use a pushbutton and  series resistor (wired in series with the 33K resistor - the pushbutton  would short it out) to decrease the frequency of IC1a, so activating  the system by means of a pushbutton switch. In this case, the radio  would be tuned to a frequency just below that of the transmitter. </li>
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Build a Radio Wave Alarm

This simple circuit is sure to have the police beating a path to your door- however, it has the added advantage of alerting you to their ...

Burglar Alarm Using LDR and BC 548

Alarm and Security 05:38

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<b><br />Description</b><br />
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               Circuit showing a Burglar Alarm.Here we have used a ldr and a switching transistor for making this circuit<br />
<a href="http://www.blogger.com/blogger.g?blogID=6157106112802119563" name="more"></a>.When the light coming towards the ldr during  the period the ldr have low resistance so the buzzer will on.When the  light going away the ldr during the period the ldr have high resistance  so the transistor will off.Here you need a 12 volt power supply<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghE-zNMfaoDvUSXTvB0NtKDEsPJCuNUvir9DZOGzCguQbQNl1EzRm_rAyElPqYJQwjualJxaeSBpb3rRKpuZDF_FYydutrBmMAxdH1o11VmK_QM2Yq52YTy1rQzYWk7novpoKmKw-qMG7o/s1600/burgel+aladr.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="317" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghE-zNMfaoDvUSXTvB0NtKDEsPJCuNUvir9DZOGzCguQbQNl1EzRm_rAyElPqYJQwjualJxaeSBpb3rRKpuZDF_FYydutrBmMAxdH1o11VmK_QM2Yq52YTy1rQzYWk7novpoKmKw-qMG7o/s400/burgel+aladr.jpg" width="400" /></a></div>
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<b> Components Required</b><br />
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      Resistor<br />
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                   10 k(preset)<br />
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      Transistor<br />
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                   BC 548<br />
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       LDR<br />
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        Buzzer<br />
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Source by : http://www.electronics-circuits.in/2012/03/burglar-alarm-ldr-bc-548.html </div>

Burglar Alarm Using LDR and BC 548

Description Circuit showing a Burglar Alarm.Here we have used a ldr and a switching transistor for making this circuit ...

Simple Rain Alarm

Alarm and Security 05:12

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GIVES BEEP WHEN WATER IS IN CONTACT WITH THE WIRE<br />
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<img height="315" src="http://www.circuiteasy.com/project_picture/rain_alarm.jpg" width="490" /></div>
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Water is a conductor of electricity. When water is in contact with  the probe then there is a flow of current which reaches to the base of  Q1. Transistor Q1 is a NPN transistor which conducts. With the  conduction of Q1 electron reaches to Q2 which is a PNP transistor .Q2  also conducts and current flows through the speaker. In a speaker there  is inductive coil which causes motion in one direction and also produce  induce current which is in opposite direction to the flow of current  this induce current in the form of pulse flows through a capacitor,  resistance and switches off Q1 and relax .this process repeats again and  again till probe is in contact with water or we can say there is a  oscillation in the circuit thus speaker diaphragm vibrates and gives a  tone. Frequency of the circuit depends on the value of Speaker Coil  impendence, Capacitor and Resistance Value.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhWNd-rkl7vQd14O9qM1GD2Vki-txFC9I5IVZUG8y-Pfmp1fdD8QH3NoRuuRcoTwVlies-7yiT_rH0ewTZArGG4bJ3J4wjK8ylKUxGqqEITmYxUDEXNbzFB4AsJj1TM6VmvGDMoRcnnnQsL/s1600/rain_alarm.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhWNd-rkl7vQd14O9qM1GD2Vki-txFC9I5IVZUG8y-Pfmp1fdD8QH3NoRuuRcoTwVlies-7yiT_rH0ewTZArGG4bJ3J4wjK8ylKUxGqqEITmYxUDEXNbzFB4AsJj1TM6VmvGDMoRcnnnQsL/s320/rain_alarm.gif" width="320" /></a></div>
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Simple Rain Alarm

GIVES BEEP WHEN WATER IS IN CONTACT WITH THE WIRE Water is a conductor of electricity. When water is in contact with the probe then t...

LIGHT ALARMS

Alarm and Security 06:34

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<b>LIGHT ALARM - 1</b><br />
This circuit operates when lightweight|the sunshine} Dependent Resistor  receives light. When no lightweight falls on the LDR, its resistance is  high and also the transistor driving the speaker isn't turned on. When  lightweight falls on the LDR its resistance decreases and also the  collector of the second transistor falls. This turns off the primary  transistor slightly via the second 100n and also the initial 100n puts a  further spike into the bottom of the second transistor. This continues  till the second transistor is turned on as onerous because it will go.  the primary 100n is currently nearly charged and it cannot keep the  second transistor turned on. The second transistor starts to turn off  and each transistors swap conditions to provide the second half of the  cycle.</div>
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<b>LIGHT ALARM - 2</b><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjgS0suZ7D5J9ukRozUww_rivabKMVoCGNR6G1TNpD-sh8iproTJxyWZwAhALyW_iDCvnvdwuff7G_JImuLyY0W4WSKelms99EMZgtoXwfMUqqLer_u_SUP6_w_Mwo7gG7l0e5nbG0JArO1/s1600/LA2.bmp" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjgS0suZ7D5J9ukRozUww_rivabKMVoCGNR6G1TNpD-sh8iproTJxyWZwAhALyW_iDCvnvdwuff7G_JImuLyY0W4WSKelms99EMZgtoXwfMUqqLer_u_SUP6_w_Mwo7gG7l0e5nbG0JArO1/s320/LA2.bmp" width="320" /></a></div>
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This circuit is comparable to lightweight Alarm -1 however produces a  louder output as a result of the speaker being connected directly to the  circuit. The circuit is essentially a high-gain amplifier that's turned  on initially by the LDR and then the 10n keeps the circuit turning on  till it will activate no more. The circuit then starts to show off and  eventually turns off utterly. the present through the LDR starts the  cycle once more. </div>
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<b>LIGHT ALARM - 3 (MOVEMENT DETECTOR)</b><br />
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This circuit is extremely sensitive and may be placed in a very space to  detect the movement of a person up to a pair of metres from the unit.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhQyoSNzkQUuqvkBd5_7hIisWAio0bfNlUJnaB3qKADwOECMBYalHVoq-bZ8ciL34e2BfH-mCONSpk9b1d3yKJ29kYHauxidxpn8b2Ygdg0qjb5LsoQZ6aYs5HszhBcCsyx90Kjopijz_JV/s1600/LA4.bmp" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="136" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhQyoSNzkQUuqvkBd5_7hIisWAio0bfNlUJnaB3qKADwOECMBYalHVoq-bZ8ciL34e2BfH-mCONSpk9b1d3yKJ29kYHauxidxpn8b2Ygdg0qjb5LsoQZ6aYs5HszhBcCsyx90Kjopijz_JV/s320/LA4.bmp" width="320" /></a></div>
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The circuit is essentially a high-gain amplifier (made of the primary 3  transistors) that is turned on by the LDR or photo Darlington  transistor. The third transistor charges the 100u via a diode and this  delivers turn-on voltage for the oscillator. The LDR has equal  sensitivity to the photo transistor during this circuit.<br />
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<a href="http://streampowers.blogspot.com/2012/07/light-alarms.html" target="_blank">http://streampowers.blogspot.com/2012/07/light-alarms.html</a> </div>
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LIGHT ALARMS

LIGHT ALARM - 1 This circuit operates when lightweight|the sunshine} Dependent Resistor receives light. When no lightweight fall...

Mains Supply Failure Alarm

Alarm and Security 03:05

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Whenever  AC mains supply fails, this circuit alerts you by sounding an  alarm.  It also provides a backup light to help you find your way to the  torch  or the generator key in the dark. The circuit is powered directly  by a  9V PP3/6F22 compact battery. Pressing of switch S1 provides the 9V   power supply to the circuit. A red LED (LED2), in conjunction with zener   diode ZD1 (6V), is used to indicate the battery power level.<br />
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Resistor  R9 limits the operating current (and hence the brightness) of  LED2.  When the battery voltage is 9V, LED2 glows with full intensity.  As the  battery voltage goes below 8V, the intensity of LED2 decreases  and it  glows very dimly. LED2 goes off when the battery voltage goes  below  7.5V. Initially, in standby state, both the LEDs are off and the  buzzer  does not sound. The 230V AC mains is directly fed to  mains-voltage  detection optocoupler IC MCT2E (IC1) via resistors R1, R2  and R3, bridge  rectifier BR1 and capacitor C1.<br />
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Illumination of the LED inside  optocoupler IC1 activates its internal  phototransistor and clock input  pin 12 of IC2 (connected to 9V via N/C  contact of relay RL1) is pulled  low. Note that only one monostable of  dual-monostable multivibrator IC  CD4538 (IC2) is used here. When mains  goes off, IC2 is triggered after a  short duration determined by  components C1, R4 and C3. Output pin 10 of  IC2 goes high to forward  bias relay driver transistor T1 via resistor  R7.<br />
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<span style="font-weight: bold;">Circuit diagram:</span></div>
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<img alt="mains supply failure alarm circuit schematic" border="0" src="http://2.bp.blogspot.com/_FdGFE8NBDgc/S-ZrBKRZGpI/AAAAAAAACk8/8sKxyTorDpY/s1600/mains-supply-failure-alarm-circuit-diagram.gif" style="height: 399px; width: 559px;" title="mains supply failure alarm circuit project" /></div>
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<span style="font-weight: bold;">Mains Supply Failure Alarm Circuit Diagram</span></div>
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Relay  RL1 energises to activate the  piezo buzzer via its N/O contact for the  time-out period of the  monostable multivibrator (approximately 17  minutes). At the same time,  the N/C contact removes the positive supply  to resistor R4. The  time-out period of the monostable multivibrator is  determined by R5 and  C2. Simultaneously, output pin 9 of IC2 goes low  and pnp transistor T2  gets forward biased to light up the white LED  (LED1).<br />
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Light provided by this back-up LED is sufficient to  search the torch or  generator key. During the mono time-out period, the  circuit can be  switched off by opening switch S1. The ‘on’ period of the  monostable  multivibrator may be changed by changing the value of  resistor R5 or  capacitor C2. If mains doesn’t resume when the ‘on’  period of the  monostable lapses, the timer is retriggered after a short  delay  determined by resistor R4 and C3.</div>
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<span style="font-weight: bold;">Source: EFY Mag</span></div>
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Mains Supply Failure Alarm

Whenever AC mains supply fails, this circuit alerts you by sounding an alarm. It also provides a backup light to help you find your...

Visitor Alarm Circuit Diagram Using IC 555

555, Alarm and Security 00:30

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<b><br /></b> <b>Description</b><br />
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                  Figure shows the circuit diagram of the 'Visitor  Alarm' . Here I have used a LDR and a mono stable Multi Vibrator for  making this circuit . When who breaking the LED ray, the LDR has high  resistance so the transistor will be OFF and the pin number two of the  IC 555 is negative then the IC 555 will be triggering so the output is  ON. When who don't breaking the LED ray, the LDR has low resistance so  the transistor will be ON and the pin number two of the IC 555 is  positive after that the IC 555 doesn't triggering so the output is OFF.</div>
<a href="http://www.blogger.com/blogger.g?blogID=6157106112802119563" name="more"></a><b><br /></b> <b>Circuit Idea</b><br />
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<img border="0" height="480" src="http://4.bp.blogspot.com/-lAvrtDRypXo/UFFBLCrYe6I/AAAAAAAABSg/k4Tuj4GGJo4/s640/visitors+alarm.bmp" width="500" /></div>
<b><br /></b><b>Making Of LDR and LED</b><br />
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           Cover both items with a black insulation tape. See the below images for further details. <br />
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LDR</center>
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<b>Arrangement Of LDR and LED</b><br />
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<b><br /></b> <b><br /></b> <b>Parts List </b><br />
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<tr><td>Component No:</td><td>Value</td></tr>
<tr><td>R1</td><td>10K</td></tr>
<tr><td>R2</td><td>10K</td></tr>
<tr><td>R3</td><td>680R</td></tr>
<tr><td>R4</td><td>10K</td></tr>
<tr><td>C1</td><td>10MF</td></tr>
<tr><td>C2</td><td>103pF</td></tr>
<tr><td>Q1</td><td>BC548</td></tr>
<tr><td>D1</td><td>White LED Or LASER</td></tr>
<tr><td><br /></td><td>LDR</td></tr>
<tr><td>U1</td><td>NE555</td></tr>
<tr><td>B1</td><td>6V Buzzer</td></tr>
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Visitor Alarm Circuit Diagram Using IC 555

Description Figure shows the circuit diagram of the 'Visitor Alarm' . Here I have used a LDR an...

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