Alarm, Detectora and Sensor
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Smoke Detector for Fire Alarm
2011-04-29 16:58:51
Smoke detector is typically used in advanced alarm systems. Most of these devices for professional use gas-detectors, ionization chambers or radioactive elements as sensors. In this circuit, we are not using any component of this complex. Instead, we use two LDR and a LED. LM1801 special purpose IC, which is specially designed for smoke detector, gives us build this circuit using the minimum number of components. It includes an internal Zener block, two outputs reference voltage, a voltage comparator, fixing the diodes and a transistor output 500mA. The smoke detector circuit is connected to the network directly. D1 rectifies the source, and R7 is reduced to the level that the circuit can operate. Capacitor C2 and zener diode voltage stabilizes within the IC regulates it. Two identical LDRs are connected in bridge type for this connection prevents the circuit from temperature changes and the effects of aging. R13 LDR and LED should be positioned so that the smoke particles to red
2011-04-29 16:58:51
Smoke detector is typically used in advanced alarm systems. Most of these devices for professional use gas-detectors, ionization chambers or radioactive elements as sensors. In this circuit, we are not using any component of this complex. Instead, we use two LDR and a LED. LM1801 special purpose IC, which is specially designed for smoke detector, gives us build this circuit using the minimum number of components. It includes an internal Zener block, two outputs reference voltage, a voltage comparator, fixing the diodes and a transistor output 500mA. The smoke detector circuit is connected to the network directly. D1 rectifies the source, and R7 is reduced to the level that the circuit can operate. Capacitor C2 and zener diode voltage stabilizes within the IC regulates it. Two identical LDRs are connected in bridge type for this connection prevents the circuit from temperature changes and the effects of aging. R13 LDR and LED should be positioned so that the smoke particles to red
Fire Alarm Using NE555
2011-04-29 16:42:40
The following circuit is an fire alarm that is quite nice and simple. This alarm function to provide early warning of fires. This alarm provides warning of fire to the user so it can be prevented early. This fire alarm circuit should be placed in places prone to fire. Fire will cause a fire which caused enough smoke that will reduce the intensity of light to the LDR, which can pass light to the surrounding environment. With decreasing light intensity will increase resistor value of the LDR and the voltage on PIN2 of IC 555 will drop to be 1-3V. This will trigger the use of bistable mode of IC 555 that cause increased voltage on pin 3 to 9V, which provides voltage to activate the Chip on Board (COB). The signal output from the COB will give sound then be amplified by an audio amplifier IC. In this circuit, the audio amplifier-wired around IC TDA 2002. The sensitivity of the circuit depends on the distance between the lamp and LDR and the creation of preset VR1. So, by placing the l
2011-04-29 16:42:40
The following circuit is an fire alarm that is quite nice and simple. This alarm function to provide early warning of fires. This alarm provides warning of fire to the user so it can be prevented early. This fire alarm circuit should be placed in places prone to fire. Fire will cause a fire which caused enough smoke that will reduce the intensity of light to the LDR, which can pass light to the surrounding environment. With decreasing light intensity will increase resistor value of the LDR and the voltage on PIN2 of IC 555 will drop to be 1-3V. This will trigger the use of bistable mode of IC 555 that cause increased voltage on pin 3 to 9V, which provides voltage to activate the Chip on Board (COB). The signal output from the COB will give sound then be amplified by an audio amplifier IC. In this circuit, the audio amplifier-wired around IC TDA 2002. The sensitivity of the circuit depends on the distance between the lamp and LDR and the creation of preset VR1. So, by placing the l
Simple Home Alarm Circuit
2010-11-12 07:31:10
Here's a simple home alarm circuit is for those who are eager to know the concept of home security system. It consists of three 555 timers gets the input from a contact that could be connected to a motion detector or any momentary contact that monitors a certain process. Once the contact is momentarily closed, the first timer which is configured as a monostable output will output a high pulse with a duration up to a maximum of 220 seconds. This output is fed into the second timer which is configured as an astable 1Hz square wave generator. The output of this second timer is then fed into the third timer to control its frequency modulation. This frequency modulation will then power a speaker and generate a siren tone similar to the police siren. The first timer U1 is configured as a monostable timer with a variable timing of up to a maximum of 220 seconds. The timing can be changed by adjusting the VR1 1M ohm potentiometer. If you need to further increase the timing, the electrolyti
2010-11-12 07:31:10
Here's a simple home alarm circuit is for those who are eager to know the concept of home security system. It consists of three 555 timers gets the input from a contact that could be connected to a motion detector or any momentary contact that monitors a certain process. Once the contact is momentarily closed, the first timer which is configured as a monostable output will output a high pulse with a duration up to a maximum of 220 seconds. This output is fed into the second timer which is configured as an astable 1Hz square wave generator. The output of this second timer is then fed into the third timer to control its frequency modulation. This frequency modulation will then power a speaker and generate a siren tone similar to the police siren. The first timer U1 is configured as a monostable timer with a variable timing of up to a maximum of 220 seconds. The timing can be changed by adjusting the VR1 1M ohm potentiometer. If you need to further increase the timing, the electrolyti
2-Zone Alarm
2009-10-09 12:01:06
This is a really small alarm that could easily fit inside a pocket. However, I also demanded reliable operation, simple construction and very low power consumption. I started with CMOS logic gates, but was soon forced to abandon the concept after a few unsuccessful (and far too complicated) takes. Then I suddenly realized that a simple transistor switch might do the job and I was right. As you can clearly see from the schematics, the circuit is utterly primitive and consists of two identical transistor switches. Each has its own alarm LED and they're coupled to a neat 82dB buzzer. The two 1N4148 diodes are used to prevent a signal from one sensor from triggering both LEDs. The sensors are connected to the jumpers. Use either loops of very thin (like 0.1mm) enamel coated wire or normally closed reed switches or even a combination of both. Since this little alarm is intended to be kept in arms reach at all times, there aren't any provisions for automatic shutdown after a certain peri
2009-10-09 12:01:06
This is a really small alarm that could easily fit inside a pocket. However, I also demanded reliable operation, simple construction and very low power consumption. I started with CMOS logic gates, but was soon forced to abandon the concept after a few unsuccessful (and far too complicated) takes. Then I suddenly realized that a simple transistor switch might do the job and I was right. As you can clearly see from the schematics, the circuit is utterly primitive and consists of two identical transistor switches. Each has its own alarm LED and they're coupled to a neat 82dB buzzer. The two 1N4148 diodes are used to prevent a signal from one sensor from triggering both LEDs. The sensors are connected to the jumpers. Use either loops of very thin (like 0.1mm) enamel coated wire or normally closed reed switches or even a combination of both. Since this little alarm is intended to be kept in arms reach at all times, there aren't any provisions for automatic shutdown after a certain peri
Rain Alarm using Water Sensor
2009-09-21 21:02:58
Rain alarm is a simple circuit using water sensor (transducer) that produces an audible alarm whenever rain falls. The circuit can be based on two transistors and or a NE555 IC. The two transistors are wired as a switch which goes on when the base of Q1 is shorted to the positive of the supply by the rainwater falling on the sensor. When the transistors are ON power supply is available to the IC1 which is wired as an astable multivibrator .The out put of IC1 drives the speaker to produce a alarm. A 555 astable multivibrator is used here which gives a tone of about 1 KHz upon detecting water. The sensor when wetted by water completes the circuit and makes the 555 oscillate at about 1kHz. The Circuits of Rain Alarm Water Sensor (Transducer)-Rain Sensing Grid Schematic It has to placed making an angle of about 30 - 45 degrees to the ground. This makes the rain water to flow through it to the ground and prevents the alarm from going on due to the stored
2009-09-21 21:02:58
Rain alarm is a simple circuit using water sensor (transducer) that produces an audible alarm whenever rain falls. The circuit can be based on two transistors and or a NE555 IC. The two transistors are wired as a switch which goes on when the base of Q1 is shorted to the positive of the supply by the rainwater falling on the sensor. When the transistors are ON power supply is available to the IC1 which is wired as an astable multivibrator .The out put of IC1 drives the speaker to produce a alarm. A 555 astable multivibrator is used here which gives a tone of about 1 KHz upon detecting water. The sensor when wetted by water completes the circuit and makes the 555 oscillate at about 1kHz. The Circuits of Rain Alarm Water Sensor (Transducer)-Rain Sensing Grid Schematic It has to placed making an angle of about 30 - 45 degrees to the ground. This makes the rain water to flow through it to the ground and prevents the alarm from going on due to the stored
Lie Detector Circuit
2009-05-10 13:00:45
This detector circuit is for detecting a Lie. The lie detector circuit diagram consists of three transistors, a capacitor, two lights or LEDs, five resistors, and a variable resistor. This Lie Detector circuit is based on the fact that a person's skin resistance changes when they sweat (sweating because they're lying). Dry skin has a resistance of about 1 million ohms, whereas the resistance of moist skin is reduced by a factor of ten or more. Resistors R1 and R2 form a voltage divider. They have resistances of 1 000 000 ohms (1 mega ohms) and, because their values are equal, the voltage at the upper probe wire is half the battery voltage (about 4.5 volts). A person holding the probe wires will change the voltage at the upper probe wire depending on their skin resistance. The skin resistance is in parallel with R2 and, because it is likely to be similar to or smaller than R2, the voltage at the probe wire will fall as skin resistance falls. Capacitor C1 functions as a smoothing ca
2009-05-10 13:00:45
This detector circuit is for detecting a Lie. The lie detector circuit diagram consists of three transistors, a capacitor, two lights or LEDs, five resistors, and a variable resistor. This Lie Detector circuit is based on the fact that a person's skin resistance changes when they sweat (sweating because they're lying). Dry skin has a resistance of about 1 million ohms, whereas the resistance of moist skin is reduced by a factor of ten or more. Resistors R1 and R2 form a voltage divider. They have resistances of 1 000 000 ohms (1 mega ohms) and, because their values are equal, the voltage at the upper probe wire is half the battery voltage (about 4.5 volts). A person holding the probe wires will change the voltage at the upper probe wire depending on their skin resistance. The skin resistance is in parallel with R2 and, because it is likely to be similar to or smaller than R2, the voltage at the probe wire will fall as skin resistance falls. Capacitor C1 functions as a smoothing ca
Audio Detector Circuit
2009-05-10 12:58:40
This electronic detector circuit is to do audio detection. The circuit is for detecting one of those 3.6khz (approx) beepers from Radio Shack. The component used is a single IC (LM324 quad op amp) and a handful of parts. Notes: The capacitor and resistor on the output of the peak detector are selected to give a reasonable decay time. I.e. so a single pulse doesn't stretch out and be miss-interpreted as an audio signal. I think I sample the output at 100ms intervals and signal a valid sound if three consecutive samples are true. The only critical parts are the trimmer, capacitors and the 560 ohm resistor in the band pass filter. The diode is not critical: any small diode will do fine. The trimmer is used to set the center frequency. I just run the beeper and adjust for the strongest output signal. It uses a condenser mic, surplus. Probably any computer microphone will do. The 4.7K resistor is a typical load for those things. Authorized by: Larry Barello, See more: Pres
2009-05-10 12:58:40
This electronic detector circuit is to do audio detection. The circuit is for detecting one of those 3.6khz (approx) beepers from Radio Shack. The component used is a single IC (LM324 quad op amp) and a handful of parts. Notes: The capacitor and resistor on the output of the peak detector are selected to give a reasonable decay time. I.e. so a single pulse doesn't stretch out and be miss-interpreted as an audio signal. I think I sample the output at 100ms intervals and signal a valid sound if three consecutive samples are true. The only critical parts are the trimmer, capacitors and the 560 ohm resistor in the band pass filter. The diode is not critical: any small diode will do fine. The trimmer is used to set the center frequency. I just run the beeper and adjust for the strongest output signal. It uses a condenser mic, surplus. Probably any computer microphone will do. The 4.7K resistor is a typical load for those things. Authorized by: Larry Barello, See more: Pres
Oxygen Sensor Simulator
2009-05-10 12:56:33
This circuit is an oxygen sensor for car. The oxygen sensor simulator as built on a protoboard. Note the cigarette lighter plug used for power source. The adjustment knob is at the left, and the switch is on the right. The red indicator LED is in the middle. Only use red, because the voltage drop of the LED is part of the circuit! The schematic diagram for the simulator. Closing the switch engages the simulator. Turning the knob clockwise simulates a lean condition, turns the LED off, and the car should start running rich to compensate. The big "V" is a digital voltmeter (not shown in the pictures). Using a smaller value for C1, perhaps 4.7 uF, will make the circuit oscillate faster and might be more like a real oxygen sensor (a new sensor switches more often than an old one). The schematic diagram for the simulator. Closing the switch engages the simulator. Turning the knob clockwise simulates a lean condition, turns the LED off, and the car should start running rich to compensate.
2009-05-10 12:56:33
This circuit is an oxygen sensor for car. The oxygen sensor simulator as built on a protoboard. Note the cigarette lighter plug used for power source. The adjustment knob is at the left, and the switch is on the right. The red indicator LED is in the middle. Only use red, because the voltage drop of the LED is part of the circuit! The schematic diagram for the simulator. Closing the switch engages the simulator. Turning the knob clockwise simulates a lean condition, turns the LED off, and the car should start running rich to compensate. The big "V" is a digital voltmeter (not shown in the pictures). Using a smaller value for C1, perhaps 4.7 uF, will make the circuit oscillate faster and might be more like a real oxygen sensor (a new sensor switches more often than an old one). The schematic diagram for the simulator. Closing the switch engages the simulator. Turning the knob clockwise simulates a lean condition, turns the LED off, and the car should start running rich to compensate.
Basic Phototransistor Detector
2009-05-10 12:56:04
This is a Phototransistor Detector circuit. In this circuit, when the light falling on the phototransistor (Q1) is blocked, its conductance will decrease and the voltage across Q1 will rise. When the voltage rises above 1/2 of the supply voltage the output of the comparator will turn ON and the LED will be lit. The only critical part of this circuit is the value of resistor R1 which in most cases can be 470K ohms but may have to be increase if the room is dark or decreased if the room is well lit. Increasing the value of R1 will cause the sensitivity of the sensor to decrease. This may be necessary when the light falling on the cell is not very strong or shadows can affect the phototransistor. There are a number of phototransistors sizes and case styles. The smaller cases will be easier to hide but connecting wires may be more difficult. Visit Basic Phototransistor Detector See More : Tire Pressure Sensor
2009-05-10 12:56:04
This is a Phototransistor Detector circuit. In this circuit, when the light falling on the phototransistor (Q1) is blocked, its conductance will decrease and the voltage across Q1 will rise. When the voltage rises above 1/2 of the supply voltage the output of the comparator will turn ON and the LED will be lit. The only critical part of this circuit is the value of resistor R1 which in most cases can be 470K ohms but may have to be increase if the room is dark or decreased if the room is well lit. Increasing the value of R1 will cause the sensitivity of the sensor to decrease. This may be necessary when the light falling on the cell is not very strong or shadows can affect the phototransistor. There are a number of phototransistors sizes and case styles. The smaller cases will be easier to hide but connecting wires may be more difficult. Visit Basic Phototransistor Detector See More : Tire Pressure Sensor
Basic CdS Photocell Detector
2009-05-10 12:55:55
This is a Basic Cadmium Sulfide (Cds) Photocell Detector circuit. In this circuit, when the light falling on the photocell (PC 1) is blocked, its resistance will increase and the voltage across PC 1 will rise. When the voltage rises above 1/2 of the supply voltage the output of the comparator will turn ON and the LED will be lit. Due to wide variations in CdS photocells it is usually best to install the cell and then measure its resistance under normal lighting conditions. A resistor with a value that is approximately 3 to 5 times the measured resistance of the cell is then selected for R1. For example; If the cell resistance is measured at 400 ohms then a 1200 to 2200 ohms resistor would be used. Increasing the value of R1 will cause the sensitivity of the sensor to decrease. This may be necessary when the light falling on the cell is not very strong or shadows can affect the photocell. This Photocell Detector circuit can be adapted for use in dark areas by placing a small light a
2009-05-10 12:55:55
This is a Basic Cadmium Sulfide (Cds) Photocell Detector circuit. In this circuit, when the light falling on the photocell (PC 1) is blocked, its resistance will increase and the voltage across PC 1 will rise. When the voltage rises above 1/2 of the supply voltage the output of the comparator will turn ON and the LED will be lit. Due to wide variations in CdS photocells it is usually best to install the cell and then measure its resistance under normal lighting conditions. A resistor with a value that is approximately 3 to 5 times the measured resistance of the cell is then selected for R1. For example; If the cell resistance is measured at 400 ohms then a 1200 to 2200 ohms resistor would be used. Increasing the value of R1 will cause the sensitivity of the sensor to decrease. This may be necessary when the light falling on the cell is not very strong or shadows can affect the photocell. This Photocell Detector circuit can be adapted for use in dark areas by placing a small light a