When power supply is restored, the lamp or the alarm is switched-off. A switch provides a “latch-up” function, in order to extend lamp or alarm operation even when power is restored.

This circuit is permanently plugged into a mains socket and NI-CD batteries are trickle-charged. When a power outage occurs, the lamp automatically illuminates. Instead of illuminating a lamp, an alarm sounder can be chosen.

Components List:

R1____________220K   1/4W Resistor
R2____________470R   1/2W Resistor
R3____________390R   1/4W Resistor
R4______________1K5  1/4W Resistor
R5______________1R   1/4W Resistor
R6_____________10K   1/4W Resistor
R7____________330K   1/4W Resistor
R8____________470R   1/4W Resistor
R9____________100R   1/4W Resistor

C1____________330nF  400V Polyester Capacitor
C2_____________10uF   63V Electrolytic Capacitor
C3____________100nF   63V Polyester Capacitor
C4_____________10nF   63V Polyester Capacitor

D1-D5________1N4007 1000V 1A Diodes
D6______________LED  Green (any shape)
D7___________1N4148   75V 150mA Diode

Q1,Q3,Q4______BC547   45V 100mA NPN Transistors
Q2,Q5_________BC327   45V 800mA PNP Transistors

SW1,SW2________SPST Switches
SW3____________SPDT Switch

LP1____________2.2V or 2.5V 250-300mA Torch Lamp Bulb
SPKR___________8 Ohm Loudspeaker
B1_____________2.5V Battery (two AA NI-CD rechargeable cells wired in series)
PL1____________Male Mains plug

Circuits Works:
Mains voltage is reduced to about 12V DC at C2’s terminals, by means of the reactance of C1 and the diode bridge (D1-D4). This avoids the use of a mains transformer.

Trickle-charging current for the battery B1 is provided by the series resistor R3, D5 and the green LED D6 that also monitors the presence of mains supply and correct battery charging.

Q2 & Q3 form a self-latching pair that start operating when a power outage occurs. In this case, Q1 biasing becomes positive, so this transistor turns on the self latching pair.

If SW3 is set as shown in the circuit diagram, the lamp illuminates via SW2, which is normally closed; if set the other way, a square wave audio frequency generator formed by Q4, Q5 and related components is activated, driving the loudspeaker.

If SW1 is left open, when mains supply is restored the lamp or the alarm continue to operate. They can be disabled by opening the main on-off switch SW2.

If SW1 is closed, restoration of the mains supply terminates lamp or alarm operation, by applying a positive bias to the Base of Q2.

Notes: Close SW2 after the circuit is plugged.

source: redcircuits.com

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Here the simple schematic of multitone siren alarm circuit. This multitone siren is effective for reverse horns, burlgar alarms, and many others. It generates five various audio tones and is much more earcatching than a single-tone siren.

The circuit is constructed around well known CMOS IC 4060 as oscillator-cum-divider and small audio amplifier chip LM386. IC 4060 is utilized as being the main part of multitone generator. A 100uH inductor is utilized at the input of IC 4060. So it oscillates within the assortment of about 5MHz RF. IC 4060 itself separates RF signals into AF and ultrasonic ranges. The audio signals of different frequencies are obtainable at pins 1, 2, 3, 13 and 15 of IC 4060 (IC1). These multifrequency signals are mixed and fed to the audio amplifier assembled close to IC LM386.

The output of IC2 is fed to the speaker via capacitor C9. If you need louder sound, use power amplifier circuit using TBA810 or TDA1010.

Only five outputs of IC1 are put to use right here since the other five outputs (pins 4 through 7 and 14) generate ultrasonic signals, that are not audible.

You may assemble the circuit on a general purpose Printed CIrcuit Board (PCB) and enclose in a appropriate cabinet. Regulated 6V-12V (or possibly a battery) could be utilized to supply the circuit to be work.

PDF version: Multitone siren alarm circuit

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Components List:

R1,R5___________ 4.7K
R2______________ 47K
R3______________ 10K
R4______________ 100K
Rx______________ *see text

C1,C4__________ 100uF/25V, electrolytic
C2,C3__________ 0.01uF (10nF), ceramic
T1_____________ 2N3702 (NTE159, TUP, etc.)
IC1,IC2________ LM/NE555, MC1455P, etc
LS_____________ Loudspeaker

This alarm circuit uses timer IC to generate frequency. The circuit has wide range supply voltage 5V to 15V DC.

*The Loudspeaker LS and the resistor marked “Rx” should be together 75 ohms. If you have a standard 8-ohm speaker then Rx is 67 ohms. The nearest value is 68 ohms. So for a 8 ohm loudspeaker Rx is 68 ohms. For a 4 ohm loudspeaker Rx is 71 ohms, for a 25 ohm loudspeaker Rx is 50 ohms, etc.

circuit diagram by Tony van Roon,
source: http://www.sentex.ca/~mec1995/circ/wailing.htm

The post Wailing Alarm Siren appeared first on Circuit Schematic Diagram.

Components List:

D1,D2,D3,D4,D5,D6,D7 : 1N4148
D8,D9                : 1N4007
ZD1                  : 2V4
R1,R2,R3,R4          : 47K
R5                   : 220K
R6,R7                : 470
R8,R9                : 10K
R10                  : 1M
C1                   : 100nF
C2,C3,C4,C5,C6       : 22uF/16V
C7                   : 470uF/16V
T1                   : BC547B
IC1                  : CD40106
IC2                  : CD4070
Buz1                 : Buzzer

Car Headlight Alarm Features:

• Continuously repeated alarm tone for lights ON (may be disabled)
• Repeated alarm tone for lights OUT
• Only 3 wires are required for hook-up

This circuit come from Velleman product kit. Download the kit manual of Velleman car headlight alarm from the following link:

Car Headlight Alarm Circuit

1 file(s) 557.34 KB

Download Kit Manual

The post Car Headlight Alarm appeared first on Circuit Schematic Diagram.

This is a car alarm simulator which using the LED as a simulation output. This simple circuit can tell you whether your car is running or not by detecting the voltage difference when the car is on and off. This occurs because when your car is running the Alternator puts a out a voltage a little bit higher than when the car is off. This circuit comes with low current consumption of 12mA max and run with 12V only.

The circuit will be activated automatically when the engine is turned off.

How to run the circuit:

1. Connect the circuit to the car electrical system.
2. Adjust RV1 until the LED flashes when the engine is not running
3. Start the engine, the LED should turn off. If the LED still on, the andjust the RV1 slighty

This circuit actually is a kits, you can get the kits at http://www.electronickits.com/kit/complete/surv/vemk126.htm. But it is very possible to you to build your own car alarm simulator circuit.

Download the car alarm simulator circuit kit manual / instruction from below link:

Car Alarm Simulator Kit Manual

1 file(s) 179.73 KB

Download Kit Manual

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FIG.l – ONE OF THREE OUTPUTS goes low depending on whether loop resistance is too high, too low, or just right.

Figure 1 shows a circuit that does the job. It”s a somewhat unusual application of a National Semiconductor LM3915 IC, normally used to drive LED” bargraph displays. That chip happens to contain the right combination of comparators and logic circuits to do what you need.

Step 1 is to translate the loop resistance into a voltage; that”s done by putting it into a voltage divider with resistors R1 and R2. Capacitor C2 protects the circuit against electromagnetic noise-important because burglar alarms use long wires, often running near heavy electrical equipment.

Step 2 is to translate the voltage into a logic signal indicating whether it”s in resisthe correct range. That”s where the LM3915 comes in. Normally, the LM3 9 15 would drive ten LEDs, one for each of ten small ranges of voltage. To obtain logic-level outputs, we have it driving 1K resistors instead of LEDs. Since we only need to distinguish three situations, not ten, we tie some of the outputs together. The LM3915 has open-collector outputs that can be paralleled in that way.

FIG.2 – THIS TRUTH TABLE shows the states of outputs A, B, and C under different loop-resistance conditions.

The truth table in Fig. 2 shows how the outputs work. Note that they use negative logic (OV for “yes”, +5V for “no”), the opposite of ordinary logic circuits. You can use inverters such as the 74HC04 to produce positive logic signals if that”s what you need.

Finally, note that the circuit will actually work with any supply voltage from 3 to 25 volts. Of course, if the supply isn”t 5 volts, the outputs will not be compatible with j-volt logic circuits.

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This is electronic bird chirp sound generator circuit which used to produce a sound like bird’s chirp.

The transformer is a small audio transformer, type LT700. The primary is center tapped with an impedance of 1Kohms at 1KHz . The secondary has an impedance of 8 ohms. The circuit works with 9V power supply.

How Electronic Bird Chirp Works

The inclusion of R1 and C1 give this oscillator its characteristic “chirp”. As the 100u capacitor charges via the 4.7K resistor, R1 the bias for the transistor is cut off. This causes the oscillation to stop, the capacitor discharges through the base emitter circuit of the transistor and oscillations start again. Altering these components alters the frequency of the chirp. The chirp is also voltage dependent. When the push button switch is operated the 100u capacitor is charged. When its released, the oscillation decays and the chirp becomes faster.

Components List:

Resistors
1 x 47k Ohm
1 x 4.7k Ohm

Transistors
1 x BC109 or BC337

Transformers
1 x 1K:8Ohm Audio Transformer

Capacitors
1 x 22nF Ceramic
1 x 10nF Ceramic
2 x 100uF Electrolytic

Other
1 x 9v Battery and Clip
1 x Plastic Board
1.5m of Copper Foil Tape
1 x C2222 8Ohm Speaker
1 x Momentary Push Switch

Download the sound sample of electronic bird chirp sound generator here

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Here is the circuit diagram of simple multitone alarm. This is a low cost circuit which is simple and easy to build. The main components of this circuit is based on dual op-amp MC1458 and LM 380. The two op amps inside the MC 1458 are used to produce square and triangular waves. LM 380 is used to amplify the output. The first op amp IC1a is wired as an astable multi vibrator and second op amp IC1b is wired as an integrator, to make the square wave triangle.

The two output square ans sine can be selected using switch S1 to the input of IC2 which amplifies it to drive the speaker. POT R4 can be used for tone adjustment.

Simple Multitone Alarm Notes

• IC1a and IC1b are same. So their power supply is common. Pin 6 of IC2 (inv input) has no connection.
• C1 and C2 are ceramic, C3 is electrolytic capacitor.
• A dual polarity power supply is needed here. Just need center tap transformer, bridge diode and an electrolytic capacitor. You may search the circuit in this site.

The post DIY Simple Multitone Alarm appeared first on Circuit Schematic Diagram.

This is a low cost, simple, yet a surprisingly powerful electronic siren powered by just a 9V battery. The circuit may provide the final circuit block module in an alarm circuit using a relay to activate it.

How The Simple Electronic Siren Work

When the switch is pressed C3 charges up through R4 with a time constant of 0.47 seconds. When the switch is released C3 begins a slower discharge through R7 and R3 with a time constant of about 5 seconds. The op amp is set up as a voltage controlled oscillator. The control voltage in this simple electronic siren circuit is the exponential rise and fall in the voltage of C3 as it charges and discharges.

When the output of the oscillator (pin 7) switches low, there is a charge remaining on C1 which holds pin 5 below the switching point. Current through R7 is proportional to the control voltage on C3. This current discharges C1 causing the voltage on pin 5 to rise towards the switching point at a rate proportional to the voltage on C3. When the switching point is reached pin 7 switches high, and initially pulls pin 6 high via C1. This causes the op amp to temporarily turn on hard. But C3 quickly recharges through D2 causing the voltage on pin 5 to fall below the switching point and causing the op amp to switch off again.

The positive pulse output from the op amp puts a fixed amount of charge into C2 slightly raising the potential of pin 6. This causes the potential on pin 6 to rise and assist the sharp switch off of the op amp. Also R5 & C2 delay the rise on pin 6 long enough to get a good output pulse.

The cycle then repeats. However, during the C3 discharge cycle the rate of charge of C1 is lower with each repetition of the oscillator (because the control voltage is lower) and the output frequency is correspondingly lower. During the C3 charge cycle the reverse applies.

The output pulses are buffered by a second op amp then the current is applied to a driver transistor. The output waveform has a low duty cycle, but gives a surprisingly loud sound.

The kit of this simple electronic siren based LM358 is available. Download the PDF version, part list included there…

PDF Manual Simple Siren Circuit Kit

1 file(s) 33.49 KB

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Initially, when the water level is below the L1 strip, supplying electrical oscillation frequency is not transferred to the diode D1. Thus the low output and LED1 does not light. Also, because the base voltage of the transistor T1 is low, it is in a state of cut-off and the collector voltage is high, which enables to produce melody IC1 (UM66) and the alarm is sounded.

When the water is just touching the L1 level detector strip, the oscillation frequency of the supply transferred to the diode D1. This straightening supply voltage and positive DC voltage developing capacitor C1, which is lit LED1. At the same time the base voltage of the transistor T1 becomes high, which makes forward bias and collector voltage falls to near ground potential. Disabling IC1 (UM66) and the alarm is inhibited.

Depending on the quantity of water present in the tank, which shows the level of the corresponding LED lights up. It thus showing medium level of water in the tank with a bar-chart style.

When the water in the tank just touching the highest level detector lines L12, DC voltage developed in capacitor C2. This makes it possible to produce a melody IC1 (UM66) and the alarm sounds again.

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