Infrared Proximity Detector Alarm Circuit schematic

This circuit can be built from readily available low-cost components, some of which may even be hiding in your junkbox! The indicated value of 22 Ω for resistor R1 causes an average current of about 65 mA through infrared emitter D1. Because the IRED is pulsed at a duty factor of about 50% through the action of T1 and IC1, a peak current of 128 mA flows during every half cycle. This may seem a lot but in fact is well within the safe specification of the LD274. The LM567 PLL IC is configured to supply a switching frequency of about 20 kHz. When the infrared beam emitted by D1 is reflected by a nearby object, IC1, through receiver diode D2 and transistor T2, receives the recovered 20 kHz signal at its input, pin 3.

 Infrared Proximity Detector Alarm Circuit Diagram:

Because the ‘567 PLL is then locked, the IC output (pin 8), drops low, triggering the 555 chip in monostable mode (IC2) and so causing acoustic actuator Bz1 to sound. The monostable remains on as long as the reflected signal is being received. Because of the presence of T3, capacitor C5 is allowed to charge only when no signal is being received. In that condition, the 555 is turned off automatically after a time determined by R9-C5. Using the component values shown, this will be about 5 seconds. Obviously D1 and D2 should be mounted such that the latter can only pick up reflected infrared light.

The choice of the two infrared components used in this circuit will be uncritical but they must be ‘band’ compatible, i.e., generate (D1) and respond to (D2) the same wavelength. The operating point of the receiver input circuit is rather dependent on ambient day-light levels and the value of R4 may need to be adjusted a little to ensure a voltage of between 1.5 V and 4 V on the collector of T1 when no signal is being received. Some dc buzzers cause a lot of back-emf so it may be necessary to insert a diode in series with the output of IC1. If necessary, this diode should preferably be a Schottky type because of the inherent low voltage drop of about 0.4 V as opposed to 0.65 V for a typical small-signal silicon diode.

Amplificateur audio 6 watts a base de TDA2613 HI FI

6 watt audio amplifier based on TDA2613 HI FI

single scheme electronic audio amplifier 6 watt base TDA2613 HI FI: Description TDA2613: An audio amplifier circuit using 6 watts TDA2613 is shown here. TDA2613 is an integrated Hi-Fi audio amplifier IC Philips Semiconductors system. CI is ON / OFF the click proof, short-circuit, thermal protection and is available online only 9-pin plastic package. In the given circuit TDA2613 is wired to operate from a single supply. Capacitor C4 is the input DC decoupler while capacitors C5, C6 are power filters. Audio input is fed to the inverting input through capacitor C4 not. Inverting input and Vp / 2 pins of the IC are tied together and connected to ground through the capacitor C3. Capacitor C2 couples the speaker to the IC output and the network comprising capacitor C1 and resistor R1 improves the high frequency stability. Amplification Scheme 6 watts using TDA2613:

Notes:. Assemble the circuit on a good quality PCB Supply Voltage (Vs) can be between 15 to 24V DC. A heat sink is necessary to TDA2613. Do not give more than 24V TDA2613. We have over circuits audio amplifiers that may interest you: 1. 30 watts audio amplifier using TDA2040 2. Circuit 10 Watt Audio Amplifier MOSFET 3. car stereo amplifier circuit 4. Watt MOSFET amplifier circuit 50

SCHEMA DOOR ALARM: ELECTRONIC REALIZATION Circuit schematic with explanation

SCHEMA DOOR ALARM: ELECTRONIC REALIZATION

AUTOMATED ASSEMBLY DOOR RING:

When the door is open, the device is triggered during a brief period and activates the buzzer is conneetee him.

When the door is closed, the device enters again function by pressing the ring for a few moments. The supply voltage must be 12 Volt DC The maximum consumption is about 70 mA with relay energizes and 3 mA onlyby rest.
To change the relay excitation time (duration of the ring), we must act on the value of the capacity C2. By increasing this value, the time increases and vice versa.
For assembly of components and connections, we must be attentive to the implementation of the scheme indications.

LIST OF ELECTRONIC COMPONENTS: All resistors are 1/4 watt unless otherwise noted. R = 4,7Kohms R2 = 33Kohms Cl = 10uF16Velec. C2 = 470uF16Velec. IC1 = 40106B RL = 2V relay 1 magnetic reed switch 1 Support 14 pin

Burglar alarm Circuit Schematic With Explanation

This is a very useful circuit diagram because these days there are lots of crimes in every where.So I suppose this would be an answer for your matter.Here I have used common Transistor BC107.After fixing this circuit switch on s1 and adjust R2 until the horn makes sound.Then switch off the s1 .Now if some one broke the thin wire the horn will make a sound.You can cover your garden with this circuit

Note

# Build this circuit on a PCB
#Don't supply more than 12V
# Use very thin wire to get good results

Car Reverse Horn Circuit Schematic With Explanation

Most of people have there own vehicles.so I suppose this circuit will be very useful circuit for them.This circuit is a car reverse horn.If you can build your own circuit for your car I think that is great.Here I have used common Music generator IC UM 66.The out put voltage of UM66 is not enough to make a good car reverse horn so by using two transistors (BC148 and BEL187)I have increased it.





Note

# This circuit operates with 12V power supply
# Build this circuit on a PCB to get good results
# use 8ohm speaker.
# Use only push to on switch.

741 op amp bassed Alarm project electronic circuit with explanation

A very simple alarm project electronic circuit can be designed using a common 741 operational amplifier IC and some other common electronic parts . As you can see in the schematic circuit , this alarm project is activated by some normal open contacts , connected in parallel . If one of those contact is closed the alarm will sound .
This alarm project is composed from an audio frequency generator , a small audio amplifier stage and a small command stage .

The audio frequency generator is designed using a 741 operational amplifier ( or some other similar type ) .The T2 and T2 transistors forms a small audio amplifier and the normal opened contacts I1to I3 forms the command stage ( you can use how many contacts you need ).
In stand-by mode when all contacts are opened T1 transistor is locked and the alarm is inactive . If one of the contact is closed T1 transistor will activate the relay that will activate alarm . One the alarm starts to sound it can not be stopped until the I contact will be opened ( the circuit will be unplugged from the power source) .

The relay used in this project must have a 12 volts nominal voltage ( 10 volts activation) with a maximum working current of 10-30mA.
This circuit project must be powered from a 12 volt DC power supply .

alarm circuit that imitates the chirping of a canary

This is a simple electronic alarm circuit that imitates the chirping of a canary. The circuit is nothing but a Hartley oscillator with few more passive components added. As the capacitor C1 charges through the resistor R1 and the transistor Q1 is driven to cut off. This makes the oscillations to stop. As the capacitor discharges through the Resistor R1 and base emitter junction of the transistor the oscillation start again. Actually the R1 and C1 are the components that make the characteristic chirping sound.
NOTES:

• Assemble the circuit on a general purpose PCB.
• The circuit can be powered from a 9V PP3 battery.
• The transformer T1 can be a audio output transformer like LT700.
• If LT700 is not available, try the audio output transformer used on you old transistor radio board.
• The speaker can be an 8 ohm tweeter.
• Switch S1 can be a push button switch.
• The chirping sound can be altered by changing the value of R1 and C1

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Fire Alarm Circuit (LOW CAST)

When there is a fire breakout in the room the temperature increases.This ultra compact and low cost fire alarm senses fire breakout based on this fact.

Transistor BC177 (Q1) is used as the fire sensor here.When the temperature increases the leakage current of this transistor also increases.The circuit is designed so that when there is an increase in the leakage current of Q1 ,transistor Q2 will get biased.As a result when there is a fire breakout the transistor Q2 will be on.The emitter of Q2 (BC 108)is connected to the base of Q3(AC 128).So when Q2 is ON Q3 will be also ON.The transistor Q3 drives the relay which is used to drive the load ie,light,bell,horn etc as an indication of the fire.The diode D1 is used as a free wheeling diode to protect it from back EMF generated when relay is switched.

NOTES:

• The Preset R1 can be used to desired temperature level for setting the alarm ON.
• This is not a latching alarm,ie;when the temperature in the vicinity of the sensor decreases below the set point the alarm stops.
• The circuit can be powered using a 9V battery or a 9V battery eliminator.
• All capacitors are electrolytic and must be rated at least 10V.
• The load can be connected through the C,NC,NO points of the relay according to your need.
• The calibration can be done using a soldering iron,and a thermo meter.Switch ON the power supply.Keep the tip of soldering iron near to the Q1.Same time also keep the thermometer close to it.When the temperature reaches your desired value adjust R1 so that relay gets ON.Done!
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Timer Alarm(SELECTIVE)

A timer circuit using IC 4060 is given here. The IC 4060 is a 14 stage binary counter with a built-in oscillator.R2, R7, C1 are the components that determine the frequency of the oscillator and the outputs will become high one after other and only one at a time. The last five outputs are only used here. The high pulses from the outputs are used to trigger the NE555 IC. Here NE555 is wired as a monostable multivibrator. The buzzer will produce the alarm when the output of IC2 goes high. The duration of the alarm depends on the components C3 and R5.The duration can be adjusted by varying the value of C3.The alarm will automatically turn OFF after the predetermined time. The trigger pin of IC2 will be normally positive. When the Q1 is forward biased by the positive pulse at its base from IC1, the capacitor C2 becomes charged and reduces the voltage at trigger pin of IC2.This triggers the IC.When the capacitor is fully charged the pin 2 becomes again positive.
The maximum duration from timer IC 4060 will be at pin 3. The times decrease by half in the pins 2, 3, 15, and 13 respectively. The timer duration can be varied by varying the capacitor C1.

NOTES:

• Use 6V DC for powering the circuit.
• Assemble the circuit on a good quality PCB.
• Mount the ICs on holders.
• The switch S2 can be a single pole five throw rotary switch.
• The switch S1 can be a push button switch.
• S1 is used to reset the timer.
• S2 is used to select the alarm time.
• R7 can be used for the fine adjustment of alarm time.

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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.

S:electronicsuite.com

Dual 555 IC Timer based Wailing Alarm Siren used as security alarm

This is Wailing Alarm Siren using Dual 555 IC Timer circuit produce warbling sound, you can use it in your toys or in security alarm. The circuit use two 555 IC oscillator. In this alarm siren circuit, the first oscillator is employed to produce audio frequency. The second oscillator is employed to produce a modulating signal. This modulating signal make this alarm siren generates warbling sound.

You can try to change the capacitor C1 to change the warbling frequency. Using the component shown in the schematic diagram, this alarm siren gives 6 seconds warbling period. You can lower the C1 capacitor value to get higher warbling frequency, for example, you can try some values between 10 uF to 47 uF to get the suitable effect. This alarm siren circuit works with 5-15V power supply, but note that the 555 IC would suffer a significant self-heating when you use 12 volts or higher, and this may cause a shorter lifetime for the 555 IC chip.

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design smoke detector alarm using the IC RE46C140 integrated circuit

Using the IC RE46C140 integrated circuit you can design smoke detector alarm using few external electronic components. The IC RE46C140 is a low power CMOS photoelectric type smoke detector IC that will provide all the required features for a photoelectric type smoke detector project .
This smoke detector alarm design incorporates a gain selectable photo amplifier for use with an infrared emitter detector pair.
An internal oscillator strobes power to the smoke detection circuitry for 100us every 10 seconds to keep standby current to a minimum. If smoke is sensed the detection rate is increased to verify an alarm condition.

An interconnect pin allows multiple detectors to be connected such that when one units alarms, all units will sound.
An internal 10 minute timer can be used for a reduced sensitivity mode. In standby the LED is pulsed on for 10mS every 43 seconds . In a local alarm condition or the push to test alarm the LED pulse frequency is increased to once every .5 seconds. In the case of a remote alarm the LED not active. In the timer mode of operation the LED is pulsed on for 10mS every 10 seconds.

A comparator compares the photo amp output to an internal reference voltage. If the required number of consecutive smoke conditions is met the device will go into local alarm and the horn will be active.
The bidirectional IO pin allows interconnection of multiple detectors. In a local alarm condition this pin is driven high immediately through a constant current source. Shorting this output to ground will not cause excessive current. The IO is ignored as an input during a local alarm.
This smoke detector circuit must be powered from a 9 volt DC power supply.

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Interesting Motorcycle Alarm

Any number of normally open switches may be used. Fit the mercury switches so that they close when the steering is moved or when the bike is lifted off its side-stand or pushed forward off its centre-stand. Use micro-switches to protect removable panels and the lids of panniers etc. While at least one switch remains closed, the siren will sound. About two minutes after the switches have been opened again, the alarm will reset. How long it takes to switch off depends on the characteristics of the actual components used. But, up to a point, you can adjust the time to suit your requirements by changing the value of C1.

The circuit board and switches must be protected from the elements. Dampness or condensation will cause malfunction. Without its terminal blocks, the board is small. Ideally, you should try to find a siren with enough spare space inside to accommodate it. Fit a 1-amp in-line fuse close to the power source. This protects the wiring. Instead of using a key-switch you can use a hidden switch; or you could use the normally closed contacts of a small relay. Wire the relay coil so that it is energized while the ignition is on. Then every time you turn the ignition off, the alarm will set itself.

alarm when the tank is full !! Water Level Sensor and Alarm Circuit using CD4066

This is Water Level Sensor and Alarm Circuit using CD4066 Circuit Schematic, for circuit not only indicates the amount of water in the tank head, but also gives an alarm when the tank is full.

This circuit uses the widely available to show IC number CD4066 bilateral switch CMOS IC to the water level through LEDs.
If the water is empty the wires in the tank are open circuit and the 180K resistors pulls the switch to open the little switches and LEDs are off. When the water begins to fill the first wire connected to the reservoir in the S1 and the + supply are shorted by water. This closes the S1 and turns the LED1 ON. As the water further into the tank, LEDS2, 3 to 4 pm light gradually filled.
No. Levels of the display to 8 if 2 can CD4066 ICs are used to increase similarly.

If the water is full, the base of the transistor BC148 is pulled up with water and saturate the transistor, turning the buzzer ON. The SPST switch has to be opened to turn off the ringer.
Remember, the switch ON while pumping water otherwise the buzzer does not sound!

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Any number of open switches used for this Motorcycle Alarm

Any number of normally open switches may be used. Fit the mercury switches so that they close when the steering is moved or when the bike is lifted off its side-stand or pushed forward off its centre-stand. Use micro-switches to protect removable panels and the lids of panniers etc. While at least one switch remains closed, the siren will sound. About two minutes after the switches have been opened again, the alarm will reset. How long it takes to switch off depends on the characteristics of the actual components used. But, up to a point, you can adjust the time to suit your requirements by changing the value of C1.

The circuit board and switches must be protected from the elements. Dampness or condensation will cause malfunction. Without its terminal blocks, the board is small. Ideally, you should try to find a siren with enough spare space inside to accommodate it. Fit a 1-amp in-line fuse close to the power source. This protects the wiring. Instead of using a key-switch you can use a hidden switch; or you could use the normally closed contacts of a small relay. Wire the relay coil so that it is energized while the ignition is on. Then every time you turn the ignition off, the alarm will set itself.

S:electronicsuite.com

NE555 timer and Water Activated Alarm circuit

This Water Activated Alarm circuit uses a NE555 timer wired as an astable oscillator and powered by the emitter current of the transistor BC109C. Under dry conditions, the transistor will from have no bias current and be fully off. As the probes get wet, a small current flows Between the base and emitter and the transistor switches on. A larger current flows in the collector circuit enabling the IC NE555 osillator to sound.

Skema Rangkaian Water Activated Alarm

Probe/contacts may use a non-reactive metal. 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 the 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).

Circuit from: www.epanorama.net

Features for simple freezer alarm circuit

Here is a simple freezer alarm circuit, but ultra sensitive with a buzzer. The circuit raises an audio alert when the temperature inside the freezer box goes up above a preset level. The circuit requires 9V dc supply and can power from a standard 9V alkaline battery.

A negative temperature co-efficient type (NTC type) small thermistor (R1) here works as the freezer status sensor. Related components (T1 and T2) are used to drive a 6 to 9V rated mechanical buzzer. When the sensor detects a temperature shoot, the buzzer starts beeping and remains in that condition, till power to the circuit is removed. For this on/off plus reset function any small dc toggle switch can be inserted at the positive rail.

Freezer Alarm Circuit

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Radio Wave Alarm This alarm circuit is sure to have the police beating a path to your door

This alarm 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.

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.

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.



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.



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.

Lead-Acid Batteries Charger with Solar Panel [Solar Batteries Charger] This Batteries Charger is intended for charging sealed lead-acid batteries with

Lead-Acid Batteries Charger with Solar Panel

This Batteries Charger is intended for charging sealed lead-acid batteries with a solar panel in small and portable applications. The customary diode that prevents the battery from discharging through the solar panel has been replaced by a FET-comparator combination.

The batteries charger will stop charging once a pre-set voltage (temperature compensated) has been reached, and recommence charging when the voltage has dropped off sufficiently. The load is disconnected when the battery voltage drops below 11V and reconnected when it gets back to 12.5V.

Solar Batteries Charger Schematic

The batteries charger circuit has the following features:

• Charges until Vbat = 13.8V (adjustable), then float charges;
• Shuts down load when Vbat <>
• Temperature compensation;
• Will work with cheap and readily available components like LM393 comparators and BUZ11 FETs;
• Uses less than 0.5mA when using TLC393 comparators;
• Burns less than 20mW in FETs when charging at 0,5A. (More expensive FETs with a lower RDSON will yield even better results). Note that the charging current is limited only by the solar panel used.

Solar Batteries Charger PCB

Note that I added three DC/DC-converters (for 9, 6 and 3V) on the PCB, the actual charger is less than half of the PCB. I don't have a silk screen, so if you want to build this, you'll have to figure out the PCB for yourself.

With all the components into place, some additional electronics to get the DC/DC-converters in and out of standby, two small SLA-batteries (2.2Ah each), some odd parts and wiring, a fuse, a front plate and housing.

A final word: you build everything at your own risk, no functionality is implied, the resulting apparatus might not work, be unfit for drying pet dogs, and contain small parts that could suffocate children when swallowed or inhaled.

Source: Solar charger for lead-acid batteries

Fire Alarm Using Thermistor In this fire alarm circuit, a thermistor works as the heat sensor. When temperature increases, its resistance decreases,

In this fire alarm circuit, a thermistor works as the heat sensor. When temperature increases, its resistance decreases, and vice versa. At normal temperature, the resistance of the thermistor (TH1) is approximately 10 kilo-ohms, which reduces to a few ohms as the temperature increases beyond 100°C. The circuit uses readily available components and can be easily constructed on any general purpose PCB.

Timer IC NE555 (IC1) is wired as an astable multivibrator oscillating in audio frequency band. Switching transistors T1 and T2 drive multivibrator NE555 (IC1). The output of IC1 is connected to npn transistor T3, which drives the loudspeaker (LS1) to generate sound. The frequency of IC1 depends on the values of resistors R5 and R6 and capacitor C2.

When thermistor TH1 becomes hot, it provides a low-resistance path to extend positive voltage to the base of transistor T1 via diode D1 and resistor R2. Capacitor C1 charges up to the positive voltage and increases the ‘on’ time of alarm. The higher the value of capacitor C1, the higher the forward voltage applied to the base of transistor T1 (BC548).

Since the collector of transistor T1 is connected to the base of transistor T2, transistor T2 provides positive voltage to reset pin 4 of IC1 (NE555). Resistor R4 is used such that IC1 remains inactive in the discharging of capacitor C1 when the thermistor connected to the positive supply cools down and provides a high-resistance (10-kilo-ohm) path. It also stops the conduction of T1. To prevent the thermistor from melting, wrap it up in mica tape.

The circuit works off a 6V-12V regulated power supply. LED1 is used to indicate that power to the circuit is switched on.

Source