Showing posts with label Alarm/Siren. Show all posts
Showing posts with label Alarm/Siren. Show all posts
Friday, August 3, 2012
Light Alarm Circuit Using LDR
This light alarm circuit is very simple and very easy to assemble even for beginners though it is not difficult. The well-known UM66 is used as the sound generator and Will give a pleasent wake up alarm.
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| Light Alarm Circuit Using LDR |
UM66 Pinout
LDR is a light dependent resistor. Normally the resistance of an LDR is very high, Sometimes as high as 1MΩ, but Pls They are illuminated with light resistance drops dramatically. In the circuit adjust the presets to the Desired 220KΩ sensitivity, meaning adjusting the threshold point where the alarms start singing.
When there is light on the light dependent resistor the transistor T1 will from the start conducting and musical UM66 powers the integrated circuit.
for more details about LDR light alarm circuit please visit http://electroschematics.com/6353/light-alarm-circuit-with-ldr/
Wednesday, November 9, 2011
LM358N - DEW Sensor
The following schematic shows a simple DEW sensor circuit diagram using LM258N IC. As the humidity around the circuit goes up, the resistance in the DEW sensor increases. When the resistance reaches a pre-specified level, the circuitry displays a warning message, and shuts down the external device
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| LM358N - DEW Sensor |
Under normal conditions, resistance of the dew sensor is low (1 kilo-ohm or so) and thus the voltage at its non-inverting terminal (pin 3) is low compared to that at its inverting input (pin 2) terminal. The corresponding output of the comparator (at pin 1) is accordingly low and thus nothing happens in the circuit.
When humidity exceeds 80 per cent, the sensor resistance increases rapidly. As a result, the non-inverting pin becomes more positive than the inverting pin. This pushes up the output of IC1 to a high level. As a consequence, the LED inside the opto-coupler is energised.
At the same time LED1 provides a visual indication. The opto-coupler can be suitably interfaced to any electronic device for switching purpose. Circuit comprising diode D2, resistors R5 and R6 and capacitor C1 forms a low-voltage, low-current power supply unit. This simple arrangement obviates the requirement for a bulky and expensive step-down transformer.
TGS813 Gas Alarm
This toxic gas alarm circuit is sensitive to less than 100 ppm of carbon monoxide. This alarm is useful for simple gas boats, sheds and cabins. You could save a life. Some of the companies listed in the Appendix to offer plans and kits for various toxic gas sensors.
Alarm of toxic gases it utilizes a tin-oxide-semiconductor. A coil of thin wire heated by a battery 12 V via IC1 and IC2, the which pulses the voltage to the coil of the sensor, saving a significant amount of energy. Zener diode Dl provides a constant voltage to the filament coil sensors. resistance of the sensor reduces the sensor is exposed to toxic gases Such as hydrogen, carbon monoxide and propane. Reduced to the resistance of the sensor, the SCR gate voltage increases. When the gate threshold voltage is reached, the SCR fires and a buzzer alarm is activated. Once activated, the bell and the switches S1 Should Be used to reset the alarm. Since the sensor has a good deal of thermal inertia, S1 must be off or open for about three or four minutes after the initial activation, allowing the sensor to stabilize, thus avoiding false alarms. Sensitivity control R7 set to the Desired value, before the activation of the SCR.
for more details about TGS813 Gas Alarm Circuit please visit http://www.free-circuit.com/toxic-gas-detector-and-alarm-circuit-with-tgs813/
Sunday, October 30, 2011
Siren Generator Circuit Using UM3561 IC
UM 3561 is a low cost siren generator designed for use in toy applications. The UM 3561 IC can generate Multi siren tones simulating Police siren, Ambulance siren, Fire brigade siren and Machine gun sound. The IC has an inbuilt oscillator and tone selection pins. It is easy to make a siren generator with only a few external components. Only one external resistor and a speaker driver transistor are sufficient to make a simple siren generator.
By changing the pin connections of Sel.1 (Pin6) and Sel. 2(Pin 1) it is easy to change the siren tones.
Sel 1Sel 2Tone
Pin 6 Pin 1
NC NC Police siren
+3V NC Fire Engine sound
Gnd NC Ambulance Siren
NC +3V Machine Gun sound
Supply voltage Min. 2.4VTyp 3V Max 3.5V
Operating current Min - -180 uA
for more details about UM3561 Siren Generator Circuit please visit http://electroschematics.com/4820/um3561-siren-generator-design-2/
Water Switch Sensor Using S201S02 IC
The following circuit shows about Water Switch Sensor circuit based on the S201S02 IC. Features: two closely spaced metal rings are used as the water sensor mechanism.
water circuit switch sensor can be used as applications for: rain alarm, watertap leak detectors, water level sensors for bathroom water heaters, wetness checker for flower pots and more.
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| Water Switch Sensor Using S201S02 IC |
Working principle of this circuit is very simple. When the sensor rings are bridged by water, an isolated electric switch turns on to activate the load (an alarm, for instance) connected through its switching contacts. Here, the renowned S201S02 solid-state relay (IC1) is wired as the electronic switch.
for more details about water switch sensor circuit please visit http://electroschematics.com/6259/water-switch-sensor-circuit/
Friday, July 1, 2011
BC548C Transistor Water Level Buzzer
This is the circuit of a simple buzzer corrosion free water level indicator for home and industries. This circuit is very simple because it uses only two transistors and some passip Components are easily found circulating in the electronics stores.
When the water reaches the sensor, BC548C Transistor base is connected to the positive terminal. In consequence the transistor is opening and the buzzer it makes a buzz. Function: In the water level indicator, buzzer will be activated in order to make a noise when a certain level of water is being reached.
Monday, May 23, 2011
Water Level Indicator With Buzzer Circuit Using Transistor
This is a simple water level indicator circuit that is based on few transistors . The circuit not only indicates the amount of water present in the overhead tank but also gives an alarm when the tank is full.
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| Water Level Indicator + Buzzer Circuit Using Transistor |
The circuit is very simple and it has a very low current consumption , so you can use a 9 volts battery to powering this water level indicator alarm . This water level indicator alarm electronic circuit can be used even for rain alarm or short circuit alarm , a resistance with a value from 0 to about 1 M ohm will trigger it . The Q1 transistor acts as a switch which applies current to the unijunction relaxation oscillator Q2 . The signal frequency of the alarm circuit is give by the values and ratios of the C1 / R2 .
If you don’t have the transistors marked on the schematic diagram you can replace them almost with any similar types.
Tuesday, March 29, 2011
CD4066 - Water Level Indicator With Alarm
This circuit is used to indicate the amount of water present in the overhead tank. Not only that, but this circuit also gives an alarm when the tank is full. CD4066 is used to indicate the level of the water through LEDs.
CD4066 - Water Level Indicator With Alarm
Quad Bilateral Switch CD4066PinOutThe circuit uses the widely available CD4066, bilateral switch CMOS IC to indicate the water level through LEDs. When the water is empty the wires in the tank are open circuited and the 180K resistors pulls the switch low hence opening the switch and LEDs are OFF. As the water starts filling up, first the wire in the tank connected to S1 and the + supply are shorted by water. This closes the switch S1 and turns the LED1 ON. As the water continues to fill the tank, the LEDs2 , 3 and 4 light up gradually. The no. of levels of indication can be increased to 8 if 2 CD4066 ICs are used in a similar fashion. When the water is full, the base of the transistor BC148 is pulled high by the water and this saturates the transistor, turning the buzzer ON. The SPST switch has to be opened to turn the buzzer OFF. Remember to turn the switch ON while pumping water otherwise the buzzer will not sound!
Thursday, March 17, 2011
Fire Alarm Circuit by Thermistor
Here is a simple fire alarm circuit based NE555 timer and use thermistor as temperature sensor. This sensor will activate the alarm when the temperature is in high value.
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 is approximately 10 kilo-ohms, which reduces to a few ohms as the temperature increases beyond 100°C. This phenomenon is employed here for sensing the fire.
Simple Fire Alarm Circuit
The NE555 is configured as a free running oscillator at audio frequency. The transistors T1 and T2 drive IC1. The output of IC1 is couples to base of transistor SL100, which drives the speaker to generate alarm sound. The frequency of NE555 depends on the values of resistances R5 and R6 and capacitance C2. When thermistor becomes hot, it gives a low-resistance path for the positive voltage to the base of transistor T1 through diode D1 and resistance R2.
[read here...]
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 is approximately 10 kilo-ohms, which reduces to a few ohms as the temperature increases beyond 100°C. This phenomenon is employed here for sensing the fire.
Simple Fire Alarm CircuitThe NE555 is configured as a free running oscillator at audio frequency. The transistors T1 and T2 drive IC1. The output of IC1 is couples to base of transistor SL100, which drives the speaker to generate alarm sound. The frequency of NE555 depends on the values of resistances R5 and R6 and capacitance C2. When thermistor becomes hot, it gives a low-resistance path for the positive voltage to the base of transistor T1 through diode D1 and resistance R2.
Saturday, March 12, 2011
Simple Photodiode Alarm
This photodiode alarm circuit can be used to give a warning alarm when someone passes through a protected area. The circuit is kept standby through a laser beam or IR beam focused on to the Photodiode. When the beam path breaks, alarm will be triggered.
Photodiode Alarm Circuit
Simple IR transmitter circuitThe circuit uses a PN Photodiode in the reverse bias mode to detect light intensity. In the presence of Laser / IR rays, the Photodiode conducts and provides base bias to T1. The NPN transistor T1 conducts and takes the reset pin 4 of IC1 to ground potential. IC1 is wired as an Astable oscillator using the components R3, VR1 and C3. The Astable operates only when its resent pin becomes high. When the Laser / IR beam breaks, current thorough the Photodiode ceases and T1 turns off. The collector voltage of T1 then goes high and enables IC1. The output pulses from IC1 drives the speaker and alarm tone will be generated.
A IR transmitter circuit is given which uses Continuous IR rays. The transmitter can emit IR rays up to 5 meters if the IR LEDs are enclosed in black tubes.
A IR transmitter circuit is given which uses Continuous IR rays. The transmitter can emit IR rays up to 5 meters if the IR LEDs are enclosed in black tubes.
This circuit from http://electroschematics.com
Thermistor Temperature Warning Alarm
A simple 7555 buzzer circuit that will activate when a preset temperature is reached. Please note that there is no hysteresis in this circuit, so that if the temperature changes rapidly, then the buzzer alarm may activate rapidly
Thermistor Temperature Warning Alarm Circuit
7555 Pinout
The Astable multivibrator using the low power CMOS timer IC 7555 which is the low power version of the popular 555 IC. The reset pin 4 of IC1 is used to activate the alarm. The astable will work only if the reset pin 4 becomes high. The reset pin is connected to the positive rail through the 10 K NTC thermister. The thermister offers high resistance in cold and its resistance becomes low to few ohms when the temperature in its vicinity increases. So when the temperature is low reset pin of IC1 remains low and astable is in off position and buzzer remains silent. When the temperature near the thermister increases, its resistance decreases and provides voltage to the reset pin of IC1 and the astable starts working.
Thermistor Temperature Warning Alarm Circuit
7555 PinoutThe Astable multivibrator using the low power CMOS timer IC 7555 which is the low power version of the popular 555 IC. The reset pin 4 of IC1 is used to activate the alarm. The astable will work only if the reset pin 4 becomes high. The reset pin is connected to the positive rail through the 10 K NTC thermister. The thermister offers high resistance in cold and its resistance becomes low to few ohms when the temperature in its vicinity increases. So when the temperature is low reset pin of IC1 remains low and astable is in off position and buzzer remains silent. When the temperature near the thermister increases, its resistance decreases and provides voltage to the reset pin of IC1 and the astable starts working.
Tuesday, February 22, 2011
Buzzer Burglar Alarm Circuit For Refrigerator
This circuit, enclosed in a small box, is placed in the fridge near the lamp. With the door closed the interior of the fridge is in the dark, the LDR R2 has a high resistance about 1000K ohm thus clamping IC1 by holding pin 12 high. When a beam of light enters from the opening, or the fridge lamp lights, the photo resistor lowers its resistance, pin 12 goes low, IC1 starts counting and, after a preset delay, the piezo sounder beeps for 20 sec. then stops for the same lapse of time and the cycle repeats until the fridge door closes. D2 connected to pin 6 of IC1 makes the piezo sounder beeping 3 times per second.
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| Buzzer Burglar Alarm Circuit For Refrigerator |
- Delay time can be varied changing C1 and/or R3 values.
- Place the circuit near the lamp and take it away when defrosting, to avoid circuit damage due to excessive moisture Don't place it in the freezer.
R1 : 10K
R2 : LDR (any type)
R3,R4 : 100K
C1 : 10nF Polyester Capacitor
C2 : 100µF/25VD1
D2 : 1N4148
IC1 : 4060
Q1 : BC337
BZ1 : Piezo sounder (incorporating 3KHz oscillator)
SW1 : SPST slide Switch
Wednesday, February 9, 2011
Low Cost Siren Using 3-Transistor
This is a low-cost siren circuit to add to our range of alarm modules. This circuit generates a tone that sounds very similar to a siren.
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| Low Cost Siren Using 3-Transistor Circuit |
A complementary transistor pair (Q2 & Q3) is wired as a high efficiency oscillator, directly driving the loudspeaker. Q1 ensures a full charge of C2 when power is applied to the circuit. Pressing on P1, C2 gradually discharges through R8: the circuit starts oscillating at a low frequency that increases slowly until a high steady tone is reached and kept indefinitely. When P1 is released, the output tone frequency decreases slowly as C2 is charged to the battery positive voltage through R6 and the Base-Emitter junction of Q2. When C2 is fully charged the circuit stops oscillating, reaching a stand-by status.
Notes:
- A good sized loudspeaker will ensure a better and powerful output tone.
- As stand-by current drawing is zero, SW1 can be omitted and B1 wired directly to the circuit.
R1,R3 : 1K C1,C2 : 22µF/25V
R2,R5 : 10K C3 : 10nF
R4 : 220R C4 : 47µF/25V
R6 : 220K Q1,Q2 : BC557
R7 : 22K Q3 : BC337
R8 : 100K
SW1 : SPST Toggle or Slide Main Switch (See Notes)
P1 : SPST Pushbutton Operating Switch
SPKR : 8 Ohm Loudspeaker
B1 : 12V Battery
Thursday, January 20, 2011
LDR Light sensitive Alarm
The circuit detects a sudden shadow falling on the light-sensor and sounds the bleeper when this happens. The circuit will not respond to gradual changes in brightness to avoid false alarms. The bleeper sounds for only a short time to prevent the battery running flat. Normal lighting can be used, but the circuit will work best if a beam of light is arranged to fall on the light-sensor. Breaking this beam will then cause the bleeper to sound. The light sensor is an LDR (light-dependant resistor), this has a low resistance in bright light and a high resistance in dim light.
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| LDR Light sensitive Alarm Circuit |
Note:
- The light-sensitivity of the circuit can be adjusted by varying the 100k preset.
- The length of bleep can be varied from 0.5 to 10 seconds using the 1M preset.
Using the 7555 low-power timer ensures that the circuit draws very little current (about 0.5mA) except for the short times when the bleeper is sounding (this uses about 7mA). If the circuit is switched on continuously an alkaline PP3 9V battery should last about a month, but for longer life (about 6 months) you can use a pack of 6 AA alkaline batteries.
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