Skema Rangkaian Alarm Monitor Sikring

Rangkaian Alarm monitor sikring ini sangatlah sederhana namun lumayan untuk mendeteksi apakah sikring telah putus atau belum. Dengan adanya lampu LED menyala berarti sikring telah putus. Kita bisa langsung menyimpulkan bahwa rangkaian tidak bekerja karena sikring telah putus. Tidak usah mengukur tegangan ada atau tidak.

Rangkaian ini cuma membutuhkan dua komponen saja yaitu Resistor bengan nilai 1k ohm dan sebuah lampu LED dipasang paralel dengan sikring. Apabila tegangan beban berlebih atau mengalami korsleting maka sikring akan putus dan lampu led otomatis menyala karena Lampu led telah mendapat tegangan.

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Rangkaian Alarm Kecepatan Mobil

Ketika kita mengemudi terkadang kita tidak mengetahui kecepatan mobil kita, apalagi ketika kita berada di jalan tol yang jalannya begitu enak dan lurus, apabila terlalu cepat atau laju mobil melebihi kecepatan bisa mengakibatkan kecelakaan yang siapapun tidak ingin terjadi. Maka diperlukanlah Rangkaian Alarm Kecepatan Mobil ini untuk mengingatkan sang sopir yang tidak memperhatikan kecepatan karena jalan yang enak dan lurus. Rangkaian inipun bisa diatur kecepatannya, misalnya kita atur ketika melebihi angka 100km/ maka alarm harus berbunyi.

Skema Rangkaian Alarm Kecepatan Mobil

Cara kerja rangkaian:
Sebuah buzzer piezo akan berbunyi. Pulsa Kecepatan dimasukkan ke dasar Q1 dan bentuk gelombang yang dihasilkan pada kolektor diberi makan melalui jaringan RC ke input dari sebuah konverter LM2917 frekuensi ke tegangan, IC1. Tegangan yang dihasilkan diumpankan ke tiga pembanding (IC2d-IC2b) yang memiliki tegangan referensi pada input pembalik mereka ditetapkan oleh 10-gilirannya trimpots VR1, VR2 & VR3. Output dari komparator setiap diterapkan melalui jaringan lain RC ke pintu gerbang dari sebuah SCR. Anoda dari tiga SCRs yang commoned terhubung ke input pembalik komparator yang tersisa, IC2a.
Non-inverting input diatur ke 2,3 V dengan trimpot VR4. Dalam penggunaannya, setelah Anda melebihi pengaturan kecepatan untuk komparator khususnya, terkait SCR sebentar melakukan menarik pin 2 dari IC2a rendah dan bunyi pendek yang dipancarkan oleh bel piezo. Kemudian, jika anda melebihi pengaturan kecepatan berikutnya, bip lain akan didengar. Idenya adalah membuat setiap setelan kecepatan beberapa km / jam lebih tinggi dari yang sebenarnya sehingga jika Anda mengemudi pada kecepatan yang benar di zona tertentu, buzzer tidak akan terdengar. Tetapi karena Anda meningkatkan kecepatan, buzzer akan berbunyi beep sekali karena Anda melebihi pengaturan kecepatan untuk setiap zona. Dengan cara ini, tidak ada kebutuhan untuk terus beralih pengaturan kecepatan seperti yang Anda melewati zona yang berbeda dan Anda dapat memilih untuk mengabaikan beep yang tidak "ilegal".

Source: extremecircuits.net

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Alarm Lemari Es

Rangkaian Alarm Lemari Es ini agar kita mengetahui apakah lemari es dalam keadaan tertutup atau tidak. Terkadang Lemari Es suka dimainkan atau dibuka tutup oleh anak-anak , dan ini mengakibatkan suhu ruangan di lemari es menurun dan akan menambah beban listrik, sehingga pemakaian listrik menjadi boros. Untuk itu maka diperlukan Rangkaian Alarm ini.

Gambar Skema Rangkaian Alarm Lemari Es

Penempatan dan Cara Kerja Rangkaian:
Sirkuit ini simpan ke dalam kotak kecil, ditempatkan di dalam lemari es di dekat lampu (jika ada) atau pembukaan. Dengan pintu tertutup bagian dalam lemari es dalam keadaan gelap, foto resistor R2 menyajikan resistansi tinggi (> 200K) sehingga menjepit IC1 dengan memegang pin 12 tinggi. Ketika seberkas cahaya masuk ketika pembukaan, atau lampu kulkas menyala, resistor foto menurunkan ketahanan (<2K), pin 12 jadi rendah, IC1 mulai menghitung, setelah penundaan yang telah ditetapkan (20 detik) piezo sounder beep berbunyi selama 20 detik. kemudian berhenti selama selang waktu yang sama dan siklus berulang sampai pintu lemari es ditutup. D2 terhubung ke pin 6 dari IC1 memungkinkan bip sounder piezo berbunyi 3 kali per detik.

Daftar Komponen:
R1____________10K 1/4W Resistor
R2___________Photo resistor (any type)
R3,R4________100K 1/4W Resistors
C1____________10nF 63V Polyester Capacitor
C2___________100µF 25V Electrolytic Capacitor
D1,D2_______1N4148 75V 150mA Diodes
IC1___________4060 14 stage ripple counter and oscillator IC
Q1___________BC337 45V 800mA NPN Transistor
BZ1__________Piezo sounder (incorporating 3KHz oscillator)
SW1__________Miniature SPST slide Switch
B1___________3V Battery (2 AA 1.5V Cells in series)

Source: www.redcircuits.com

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Rangkaian Alarm Sepeda Motor Sederhana

Alarm Motor Sederhana- Setelah saya amati keinginan para pembaca saya mencoba menyimpulkan bahwa kebanyakan pembaca mayoritas menyukai rangkaian yang sederhana semisal Alarm sepeda motor ini yang saya kutip dari dytoshareforum.forumotion.net. Rangkaian Alarm ini sangat sederhana sekali, siapapun pasti bisa memasangnya. Silahkan disimak....
       Alarm berguna untuk menghindari terjadinya pencurian sepeda motor. Berikut ini akan saya tuliskan bagaimana membuat alarm sendiri. Sirine dari alarm keamanan adalah menggunakan klakson yang sudah ada pada motor anda.

Cara kerja dari alarm yang saya buat ini adalah mematikan arus CDI sehingga mesin tidak dapat dihidupkan. Apabila kunci kontak dipaksa berada pada posisi ‘ON’ maka klakson akan berbunyi secara terus menerus walaupun kunci kontak dikembalikan pada posisi ‘OFF’ klakson akan tetap berbunyi. Hal ini pasti akan membuat sang pencuri menjadi panik dan memilih untuk kabur, hahaha...

Alat yang perlu disiapkan:
1. Solder dan timah
2. Gunting
3. Isolasi kabel

Bahan yang perlu disiapkan:
1. Saklar (switch) 3 kaki..........Rp 2.500
2. Relay 4 kaki......................Rp 15.000
3. Soket relay.......................Rp 5.000
4. Kabel 3 meter....................Rp 4.500

Diagram kelistrikan alarm:

Memasang saklar alarm:
Saklar alarm diletakkan pada daerah yang sulit dijangkau yaitu dibawah jok, seperti pada gambar dibawah. Potong kabel negatif CDI yang berwarna hitam bergaris putih, lalu sambungkan ke saklar alarm yang berkaki 3. Perhatikan posisinya!! Kabel dari cdi menuju ke saklar dipasang pada kaki nomer 1 (pinggir) sedangkan kabel dari potongan cdi menuju bodi itu dipasang pada kaki nomer 2 (tengah). Kemudian siapkan kabel panjang pada kaki nomer 3 (pinggir) menuju klakson, biarkan dahulu kita lanjut langkah memasang relay dulu yee..

Memasang relay:
Pasang relay pada soketnya, satukan kaki nomer 86 dengan kabel panjang dari saklar alarm yg tadi telah disiapkan, kemudian sambung ke negatif klakson (kabel klakson berwarna hijau). Sambung kaki nomer 30 dan 85 menjadi satu, lalu disambung ke positif klakson (kabel klakson berwarna oranye). Kaki nomer 87 dipasang ke aki, yaitu kabel merah pada soket berwarna hijau.

Pengetesan:
Selesai merakit rangkaian diatas, ada baiknya kita melakukan pengetesan sistem alarm yang kita buat itu.

Pertama, posisikan saklar alarm berada pada posisi OFF, kemudian nyalakan kunci kontak pada posisi ON (seharusnya tidak terjadi apa2). Kemudian hidupkan mesin (seharusnya mesin dapat hidup dengan sempurna), lakukan pengetesan pada klakson, teeet teeet teeet (seharusnya klakson dapat berfungsi normal). Jika semua terasa baik kemudian matikan kunci kontak pada posisi OFF.

Kedua, posisikan saklar alarm berada pada posisi ON, kemudian nyalakan kunci kontak pada posisi ON (seharusnya klakson akan berbunyi). Kemudian coba hidupkan mesin (seharusnya mesin tidak dapat dihidupkan). Langkah terakhir adalah mematikan kunci kontak ke posisi OFF (seharusnya klakson akan tetap berbunyi, berbunyi, dan teruuus berbunyi...)

Langkah terakhir adalah mematikan bunyi klakson alarm yang sanggup membuat telinga bergetar, bergetar dan bergetar... Cabut kunci kontak, buka jok, kemudian matikan alarm dengan memindahkan saklar alarm ke posisi OFF.

Demikian ulasan tentang uraian singkat sistem alarm pada sepeda motor. Semoga bermanfaat gan, Thanks...

http://dytoshareforum.forumotion.net

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Alarm Sepeda Motor Sensor Magnet

Rangkaian Alarm Sepeda Motor | Pengaman Sepeda Motor ini sangat bermanfaat sekali untuk mengamankan sepeda motor kesayangan anda, orang lain tidak akan bisa mengoperasikannya meskipun kita berikan kunci motornya yang ada hanya alarm yang berbunyi namun motornya tidak bisa dioperasikan baik dengan starter maupun dengan kick starter, sehingga pencuri pun akan kaget dan segera meninggalkan motor anda. Hanya anda sendiri yang bisa mengoperasikannya karena sensor penggeraknya ada pada anda.

Skema Rangkaian Alarm Sepeda Motor

Penyambungan Kabel

A  : Ke Accu
B  : Ke kontak setelah dipotong
C  : Ke Pulser
D  : Ke sistem pengapian CDI, elektrik starter, lampu rem, lampu sign dsb.
E  : Ke massa

CARA KERJA RANGKAIAN :
Rangkaian dibuat sedemikian rupa sehingga saat standby maupun saat dioperasikan betul-betul tidak berpengaruh terhadap kinerja sepeda motor tersebut. Rangkaian akan bekerja saat kontak di ON kan.
Saat kunci kontak di ON kan arus dari accu melalui kunci kontak dan S2 akan langsung ke alarm (AL) yang dikendalikan oleh SCR 2P4M.
Sementara itu secara bersamaan arus juga akan ke titik B dan ke gate SCR melalui resistor 47 K ohm yang akan memicu SCR dan langsung akan menyebabkan SCR tersebut bekerja. Dengan demikian SCR akan ON dan alarm (AL) akan mendapat tenaga dan berbunyi.
Meskipun kontak di OFF kan sirine akan tetap dioperasikan karena SCR mengunci (laching). Bersamaan dengan itu rangkaian relay yang dikendalikan oleh transistor 1 dan 2 belum bekerja, sehingga titik C yang dihubungkan ke pulser sepeda motor tetap akan di hubung singkatkan ke ground melalui S2. (untuk sepeda motor dengan pengapian DC, titik C boleh ditiadakan).
Hal ini memungkinkan sepeda motor tidak akan dapat di start baik dengan elektrik maupun kick starter.
Uraian di atas sangat jelas merupakan langkah pengamanan sepeda motor, alarm (AL) berbunyi sementara motor tidak dapat dioperasikan.
Untuk mengoperasikannya kontak harus di ON kan lagi bersamaan dengan mendekatkan magnet pada reed switch.
Reed switch akan dihubungkan dan melalui resistor 47 K ohm, reed switch dan resistor 1 K ohm akan ke basis transistor 1 dan sekaligus meng ON kan transistor 1, demikian juga transistor 2.
Dengan ON nya transistor 1 dan 2 menyebabkan relay mendapat tenaga, dan kontak-kontak pada relay akan berpindah posisi.
Tegangan yang pada mulanya ke alarm (AL) akan diputuskan sehingga alarm berhenti, bersamaan dengan itu pulser juga diputuskan dari ground.
Hal lain yang terjadi titik D akan dihubungkan dengan tegangan dari accu yang berfungsi mengunci kerja transistor 1 dan 2 dan sekaligus memberikan tegangan pada sistem kelistrikan pada sepeda motor tersebut, misalnya elektrik stater, pengapian CDI dll.

CARA PENGOPERASIAN
Untuk menyalakan sepeda motor tempatkan magnet kecil pada tempat sensor (reed switch) bersamaan dengan meng ON kan kunci kontak.
Sesaat setelah di ON kan akan terdengar alarm berbunyi tetapi hanya sesaat saja, dan sepeda motorpun siap untuk dioperasikan.

PERAKITAN DAN PENEMPATAN RANGKAIAN
Rangkaian harus dirangkai dan dikemas sedemikian rupa sehingga tahan terhadap guyuran air terutama pada saat sepeda motor tersebut dicuci.
Untuk menempatkan rangkaian harus ditempatkan pada tempat yang tidak mudah untuk dibongkar dan sifatnya rahasia terutama tempat sesor (reed switch) sehingga hanya kita yang dapat mengetahui dan mengoperasikan sepeda motor tersebut.

Untuk sepeda motor jenis Mio pengalaman saya Sensor Reed Switch disimpan dibawah injakan kaki. Penutup bawah injakan bisa anda buka untuk menanam sensor didalamnya, sehingga aman dari guyuran air saat motor dicuci. Untuk magnet sebagai penggerak Relay Reed Switch simpan dibawah sendal atau sepatu, sehingga orang lain tdk tahu penggeraknya ada dimana. Pengalaman saya lucu juga ketika orang lain saya suruh starter namun gak bisa bisa padahal ya itu tadi orang lain tidak punya magnet dibawah sendalnya..haha..

Selamat Mencoba, Semoga berhasil!!

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Alarm Sentuh (Touch Alarm)

This is a touch activated alarm system. Your alarm system will be activated when someone touching the "trigger". You may use this circuit at your home door, your vehicle etc.

Skema Rangkaian Alarm Sentuh

Parts list:

R1 = 100K R2 = 56K R3 = 10M R4 = 220K P1 = 100K D1 = 1N4004

T1 = 2N3904, or equivalent U1 = 555 Timer* C1 = 47μF/16V** C2 = 33μF/16V** Re1 = Relay***

Notes:

*The 555 can be a LM, NE, or MC(cmos) type, they're all pin-compatible.

**C1/C2's working voltage ought to be elevated to 25V in the event you decide to go with a 12V power source. Rule of thumb: the operating voltage of capacitors are at least double the supplied voltage, in other words, if the power source is 9 Volt, your capacitor(s) is a minimum of 18V. Transistor T1 could be any approximate substitute.

*** Use any appropriate relay for the project and if you're not tight on area, use any size. I've build this specific circuit to prevent students from fiddling using the security cameras in pc labs at the University I'm employed. I made sure the metal casing was not grounded. But as being the schematic shows you are able to essentially hook it as much as any type of metal surface. I utilized a 12-vdc power supply. Use any suitable relay to deal with your specifications. A 'RESET' switch (Normally Closed) can be added between the constructive and also the 'arrow-with-the-+'. The trigger (touch) wire is connected to pin 2 of the 555 and will trigger the relay, using the body resistance, when touched. It is apparent that the 'touching' component has to be clean and can make good contact using the trigger wire. This particular circuit might not be suitable for all applications. Just in case you wonder why pin 5 is not listed within the schematic diagram; it is not really required. In particular noisy circumstances a little ceramic capacitor is placed between pin 5 and ground. It will no harm to put one or leave it out.

Additional note: For those of you who didn't discover, there's an approximate 5-second delay build-in before activation of the relay to avoid false triggering, or perhaps a 'would-be' thief, and so on.

Circuit design by Tony van Roon.

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Alarm Circuit For Motorcycle using CD4001

 Simple Alarm for motorcycle with a CD4001

This is a simple alarm circuit for a check with a 4001. You can use it to protect our home, motorcycle, car or any other application that comes to mind. In this circuit you will make a computer simulation with Livewire and then design the printed circuit Kicad.

OPERATION
SW1 is a normally closed switch when pressed triggers the flip-flop formed by the two NOR gates of the CD4001 and remains in that state for a time determined by the time constant of R5-C2. This time is the one who keeps the relay RL1 and operated by its two contacts that we investors will control two loads, for example a siren and a light or any other that we connect to P3 and P4.
After that time elapsed, the relay disconnects the circuit will soon be the alarm to be triggered again.

We can replace the switch Sw1 a PIR motion sensor, an infrared barrier, a smoke detector, gas detector, a magnetic sensor, a panic button or other device to act as a switch closed and opened fire at the alarm.

PRINTED CIRCUIT DESIGN

For the circuit we can only practical substitute for a preset R5 (RV1) so you can easily adjust the monitor while the charges.

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Alarm Suhu Tinggi BC550

High Temperature Alarm Circuit

The circuit is small regulator of 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

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Broken Charger Connection Alarm

Broken Charger Connection Alarm Circuit Diagram

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.

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Sensor IC LM35 based Overheat Detector Alarm Switch

This is Overheat Detector Alarm Switch using Temperature Sensor IC LM35 Electronic Suite Diagram, at the heart of this overhead detector (fire alarm) circuit is a precision integrated temperature sensor type LM35 (IC1), which provides an accurately linear and directly proportional output in mV, over the zero to +155 degrees C temperature range. This can be used as part of fire smoke detectors but do not use it as a home fire alarm system.
The LM35 develops an output voltage of 10 mV/K change in measured temperature.
Designed to draw a minimal current of its own,
the LM35 has very low self heating in still air.
Here the output of the LM35 is applied to the non-inverting input of a comparator wired around a CA3130 opamp (IC2). A voltage divider network R3-P1 sets the threshold voltage, at the inverting input of the opamp. The threshold voltage determines the adjustable temperature trip level at which the circuit is activated.
When the measured temperature exceeds the user-defined level, the comparator pulls its output High to approx. 2.2 V causing transistor T1 to be forward biased instantly. T2 is also switched on, supplying the oscillator circuit around IC3 with sufficient voltage to start working. The 555 set up in astable mode directly drives active piezoelectric buzzer Bz1 to raise a loud alert. Components R7, R8 and C4 determine the on/off rhythm of the sounderA transistor based relay driver may be driven off the emitter of T1 (TP1). Similarly, replacing the piezo sounder with a suitable relay allows switching of high-power flashers, sirens or horns working on the AC mains supply.

Source: electrosuite.com

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Rangkaian Alarm Garasi

This is a simple single-zone burglar alarm circuit. Its features include automatic Exit and Entry delays. 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.

It has an extremely small standby current – making it ideal for battery-powered operation. I’ve used a 9-volt battery in the diagram – but the circuit will work at anything from 5 to 15-volts. Just choose a relay and Siren suitable for the voltage you want to use.
It’s easy to use. To set the alarm move SW1 to the “set” position. You now have about 10 to 15 seconds to leave the building. When you return and open the door – the green LED will light. You then have about 10 to 15 seconds to move SW1 to the “off” position. If you fail to do so – the relay will energize and the Siren will sound. Of course – you can turn the Siren off at any time by moving SW1 to the “off” position.
Because of manufacturing tolerances – the precise length of any delay depends on the characteristics of the actual components you’ve used in your circuit. But by altering the values of R5 & R6 you can adjust the Exit and Entry times to suit your requirements. Increasing the values increases the time – and vice-versa.

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Rangkaian Sirine Sederhana 2 Transistor

This is a simple Siren circuit used 2 transistor . The siren circuit produced imitates the rise and fall of an American police siren. When first switched on the 10u capacitors is discharged and both transistors are off. When the push button switch is pressed to 10u capacitor will charge via 22k resistor. This voltage is applied to the base of the BC108B which will turn on slowly. When the switch is released the capacitor will discharge via the 100k and 47k base resistors and the transistor will slowly turn off. The change in voltage alters the frequency of the siren.

Skema rangkaian sirine sederhana

Current drain is fairly high in this circuit so a suitable power supply is required. The duration the tone takes to rise and fall is determined by the 10u and 22k resistor. These values may be varied for different effects.

Transistor 2N3702 description

This device designed for use as PNP general purpose amplifier and switches requiring collector currents to 300mA.



Absolute Maximum Ratings

• Collector-Emitter Voltage (VCEO ): -25 V.
• Collector-Base Voltage (VCBO ): -40 V.
• Emitter-Base Voltage (VEBO ): -5.0 V.
• Collector Current - Continuous (IC): -500 mA.
• Operating and Storage Junction Temperature Range (TJ, TST): -55 ~ +150 C.
• Current Gain (hFE DC ): 60 - 300.

Pin transistor BC 108

• Low current (max. 100 mA).
• Low voltage (max. 45 V).
• Current Gain (hFE DC) : 110 - 450.

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Dark Detector (Deteksi Kegelapan)

The dark detector circuit shown here can be used to produce an audible alarm when the light inside a room goes OFF. The circuit is build around timer IC NE555.A general purpose LDR is used for sensing the light. When proper light is falling on the LDR its resistance is very low. When there is no light the LDR resistance increases. At this time the IC is triggered and drives the buzzer to produce an alarm sound. If a transistor and relay is connected at the output (pin3) of IC1 instead of the buzzer, electrical appliances can be switched according to the light.


Notes

• The LDR ,R4 can be any general purpose LDR.
• The circuit must be assembled on a good quality PCB or common board.
• The circuit can be powered from a 9V PP3 battery.
• The POT,R3 can be sued as a volume controller.
• Mount the IC1 on a holder.It will make replacements easy.

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5 Zone Alarm System

Each zone 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.

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Water Activated Alarm (Alarm Deteksi Air)

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. However as the probes get wet the transistor will conduct and sounding the alarm.


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).

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Water Level Alarm (Alarm Ketinggian Air)

This circuit will produce an audible alarm when the water level reaches a preset level.The circuit can be powered of a 3V battery and is very handy to use.


The circuit is based on an astable multivibrator wired around IC1 (NE 555).The operating frequency of the astable multivibrator here will depend on capacitor C1, resistances R1,R2 and the resistance across the probes A&B.When there is no water up to the probes,they will be open and so the multivibrator will not produce oscillations and the buzzer will not beep.When there is water up to the level of probes,some current will pass through the water,the circuit will be closed to some extend,and the IC will start producing oscillations in a frequency proportional to the value of C1,R1,R2 and the resistance of water across the probes.The buzzer will beep to indicate the presence of water up to the level of the sensing probes.


Notes

• The circuit can be powered of a 3V battery.
• Assemble the circuit on a good quality PCB or common board.
• The probes can be made of two insulated copper Aluminiun wires.
• Place the probes at the position where you have to sense the level.

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Alarm Kegagalan Power Suplay (Power Supply Failure Alarm)

Power supply failure indicator circuits

Most of the power supply failure indicator circuits need a separate power supply for themselves. 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 supply fails.


Operation

Whenever the supply fails, resistor R1 pulls the base of transistor low and saturates it, turning the buzzer ON.

Notes

• This circuit can be used as an alarm for power supplies in the range of 5V to 15V.
• The piezo buzzer needs to be an active type (not a piezo diaphragm).
• The purpose of the diode is to prevent the charge on the electrolytic being passed to any other part of the circuit when the power fails.

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Theft-Preventer-Alarm (Alarm anti maling)

 This circuit utilising a 555 timer IC can be used as an alarm system to prevent the theft of your luggage, burglars breaking into your house etc. The alarms goes ON when a thin wire, usually as thin as a hair is broken.
The circuit is straightforward. It uses a 555 IC wired as an astable multivibrator to produce a tone of frequency of about 1kHz which gives out a shrill noise to scare away the burglar.
The wire used to set off the alarm can be made of a thin copper wire like SWG 36 or higher.
You can even use single strands of copper form a power cable.

The circuit operates on a wide range of voltages from 5V to 15V.
The speaker and the circuit could be housed inside a tin can with holes drilled on the speaker side for the sound to come out.

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FM radio-controlled anti-theft alarm

This FM radio-controlled anti- theft alarm can be used with any vehicle having 6- to 12-volt DC supply system. The mini VHF, FM transmitter is fitted in the vehicle at night when it is parked in the car porch or car par







 
The receiver unit with CXA1019, a single IC-based FM radio module, which is freely available in the market at reasonable rate, is kept inside. Receiver is tuned to the transmitter's frequency. When the transmitter is on and the signals are being received by FM radio receiver, no hissing noise is available at the output of receiver. Thus transistor T2 (BC548) does not conduct. This results in the relay driver transistor T3 getting its forward base bias via 10k resistor R5 and the relay gets energised. When an intruder tries to drive the car and takes it a few metres away from the car porch, the radio link between the car (transmitter) and alarm (receiver) is broken. As a result FM radio module gene-rates hissing noise. Hissing AC signals are coupled to relay switching circ- uit via audio transformer. These AC signals are rectified and filtered by diode D1 and capacitor C8, and the resulting positive DC voltage provides a forward bias to transistor T2. Thus transistor T2 conducts, and it pulls the base of relay driver transistor T3 to ground level. The relay thus gets de-activated and the alarm connected via N/C contacts of relay is switched on. If, by chance, the intruder finds out about the wireless alarm and disconnects the transmitter from battery, still remote alarm remains activated because in the absence of signal, the receiver continues to produce hissing noise at its output. So the burglar alarm is fool-proof and highly reliable

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Light Control Alarm (Rangkaian Pengontrol Lampu)

Jika LDR tidak mendapat cahaya maka tegangan R4 cukup kecil sehingga TR3 OFF. Tegangan R6 yang terhubung pada gate SCR akan besar sehingga SCR aktif. Alarm berbunyi terus walupun tegangan R6 sudah 0 volt. Untuk mematikan alarm digunakan switch reset.

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