Combustible gas alarm circuit diagram 7812 7805 555
#gas sensor
#voltage regulator
#555 timer
#comparator
#alarm circuit
#7812
#7805
#buck regulator
#transformer
#safety
Description: The circuit consists of a buck rectifier and voltage regulator, a gas sensor, a comparator circuit, and an alarm sound circuit. The buck regulator circuit includes a transformer, a bridge rectifier, and components such as QL, IC3 (7812), and IC4 (7805). The gas sensor is a semiconductor type, specifically the QM-N5 or MQ-N series. The comparator utilized is a dual voltage comparator, LM393 (IC1). The audio alarm circuit is based on the 555 timer (IC2), which drives a speaker (Y) and an LED. When the concentration of flammable gas exceeds a certain threshold, the resistance of the semiconductor gas sensor (QM-N5) decreases, resulting in an increase in the voltage at the input of the comparator (IC1). When this voltage exceeds the reference voltage, IC1 outputs a high signal, triggering the 555 timer. The 555 timer, configured with resistors R3, R4 and capacitor C1, generates an oscillation frequency of approximately 1000 Hz. This output activates the speaker to produce a 1 kHz alarm sound and causes the LED to flash. Conversely, when the gas concentration is within normal limits, the resistance of the gas sensor increases significantly, causing the voltage at the comparator input to drop. This results in a low output from IC1 (approximately 0.7 V), resetting the 555 timer and silencing the alarm circuit. The alarm system is designed to emit audible and visual signals when flammable gas concentrations exceed 0.04%.
The described circuit operates by integrating multiple components to create a reliable gas detection and alarm system. The buck rectifier converts the AC voltage from the transformer into a stable DC voltage suitable for powering the circuit. The voltage regulators (IC3 and IC4) ensure that the circuit operates within safe voltage levels, providing 12V and 5V outputs respectively for various components.
The gas sensor, either the QM-N5 or MQ-N type, is sensitive to specific flammable gases. It functions by changing its resistance in response to the concentration of gas in the environment. The comparator circuit, using the LM393, continuously monitors the voltage generated by the gas sensor. When the gas concentration rises above the defined threshold, the comparator's output transitions from low to high, activating the alarm system.
The 555 timer, a versatile integrated circuit, is configured in astable mode to generate a square wave output. The frequency of oscillation is determined by the values of resistors R3 and R4, and capacitor C1, allowing for flexibility in tuning the alarm frequency. The output from the 555 timer is used to drive the speaker, producing an audible alarm at 1 kHz, which is significant enough to alert individuals nearby. The LED serves as a visual indicator, providing an additional layer of notification.
In summary, this gas detection alarm circuit is a well-designed system that effectively combines various electronic components to ensure timely alerts in the presence of flammable gases, enhancing safety in environments where such gases may pose a risk. As shown in FIG alarm by a buck rectifier and voltage regulator circuit, gas sensor, comparator circuit and sound the alarm circuit. Buck regulator circuit by a transformer rec tifier and B, the bridge rectifier circuits QL, IC3 (7812), IC4 (7805) and other components. Gas-sensitive semiconductor sensor QM-N5-type or MQ-N-type devices. Comparator IC1 dual voltage comparator LM393. Audio alarm circuit consists of IC2 (555), speaker Y, LED and other components. When the concentration of flammable gas exceeds a certain value, between AB pole semiconductor gas device resistance becomes small, the partial pressure of the resistance R1 increases, the potential of the corresponding comparator IC1 foot rises, and when the above feet when the reference voltage value, IC1 output high, the 555 set, while 555 and R3, R4, C1 composed of the oscillator starts oscillation frequency f 1.44/(R3 + 2R4) C1, as shown in FIG. parameters corresponding to a frequency of about 1000Hz. 555 signal output pin push speaker Y issued lkHz sound alarm signal, and the LED lamp flashes. When the concentration of flammable gas is normal, between the AB QM-N5 resistance becomes very large, the partial pressure resistor R1 becomes smaller, the potential reduction of the corresponding IC1 foot, IC1 output low ( 0.7V), 555 Reset, the alarm circuit does not occur.The alarm circuit sends out the concentration of flammable gas is higher than 0.04% audible and visual alarm signals to alert the owner attention.
The described circuit operates by integrating multiple components to create a reliable gas detection and alarm system. The buck rectifier converts the AC voltage from the transformer into a stable DC voltage suitable for powering the circuit. The voltage regulators (IC3 and IC4) ensure that the circuit operates within safe voltage levels, providing 12V and 5V outputs respectively for various components.
The gas sensor, either the QM-N5 or MQ-N type, is sensitive to specific flammable gases. It functions by changing its resistance in response to the concentration of gas in the environment. The comparator circuit, using the LM393, continuously monitors the voltage generated by the gas sensor. When the gas concentration rises above the defined threshold, the comparator's output transitions from low to high, activating the alarm system.
The 555 timer, a versatile integrated circuit, is configured in astable mode to generate a square wave output. The frequency of oscillation is determined by the values of resistors R3 and R4, and capacitor C1, allowing for flexibility in tuning the alarm frequency. The output from the 555 timer is used to drive the speaker, producing an audible alarm at 1 kHz, which is significant enough to alert individuals nearby. The LED serves as a visual indicator, providing an additional layer of notification.
In summary, this gas detection alarm circuit is a well-designed system that effectively combines various electronic components to ensure timely alerts in the presence of flammable gases, enhancing safety in environments where such gases may pose a risk. As shown in FIG alarm by a buck rectifier and voltage regulator circuit, gas sensor, comparator circuit and sound the alarm circuit. Buck regulator circuit by a transformer rec tifier and B, the bridge rectifier circuits QL, IC3 (7812), IC4 (7805) and other components. Gas-sensitive semiconductor sensor QM-N5-type or MQ-N-type devices. Comparator IC1 dual voltage comparator LM393. Audio alarm circuit consists of IC2 (555), speaker Y, LED and other components. When the concentration of flammable gas exceeds a certain value, between AB pole semiconductor gas device resistance becomes small, the partial pressure of the resistance R1 increases, the potential of the corresponding comparator IC1 foot rises, and when the above feet when the reference voltage value, IC1 output high, the 555 set, while 555 and R3, R4, C1 composed of the oscillator starts oscillation frequency f 1.44/(R3 + 2R4) C1, as shown in FIG. parameters corresponding to a frequency of about 1000Hz. 555 signal output pin push speaker Y issued lkHz sound alarm signal, and the LED lamp flashes. When the concentration of flammable gas is normal, between the AB QM-N5 resistance becomes very large, the partial pressure resistor R1 becomes smaller, the potential reduction of the corresponding IC1 foot, IC1 output low ( 0.7V), 555 Reset, the alarm circuit does not occur.The alarm circuit sends out the concentration of flammable gas is higher than 0.04% audible and visual alarm signals to alert the owner attention.
Explosive gas detector circuit diagram
A gas sensor (from Allegro Electronics, Cornwall Bridge, CT06754 Ts GS823) activates in the presence of explosive gas. U5 functions as a voltage-to-frequency converter, with the sensor producing a frequency that is proportional to conductance. The output frequency varies from...
Sequential Flasher
A 555 timer is used to drive a CMOS counter in this device, which employs an RCA CA3079 zero-voltage switch to control triacs TR1 through TR4. This circuit can be utilized for sequencing lamp displays, among other applications. Caution is...
Create a flash-then-steady LED using a 555 timer
The circuit illustrated briefly flashes an LED to attract attention and remains illuminated as long as power is supplied. The circuit utilizes the well-known 555 timer integrated circuit (IC) configured as a standard astable multivibrator with resistors RA, RB, and...
Electronic Roulette wheel with 20 LEDs and with 36 LEDs
In this electronic roulette wheel, the 555 timer functions as a pulse generator with a fading frequency. The 4017 counter activates LEDs sequentially in the selected string, while a D-type flip-flop (4013 IC) serves as a divider by two to...
Grand Prix Starting Lights
This circuit replicates the starting light sequence used by FISA in Formula One racing. It can be utilized with slot car sets (such as HO scale AFX, Life Like, or Tyco sets) or radio-controlled cars. The circuit employs a 555...
hobby power supply circuit
The circuit utilizes the 7805 voltage regulator, which features three connections: input, output, and ground. It delivers a fixed output voltage, with the last two digits of the part number indicating the specific output voltage, such as 05, 06, 08,...
Intermittent start-stop cycle control circuit of seven b
The circuit, as illustrated in Figure 3-82, employs a 555 IC to control a motor automatically, managing its start and stop cycles. The running and stopping times of the motor can be adjusted by modifying the values of potentiometers RPi...
Extend Timer Range For The 555
Anyone who has designed circuits using the 555 timer chip has, at some point, wished for the ability to program longer timing periods. Timing intervals exceeding a few minutes are challenging to achieve due to the significant impact of component...
Frequency-detecting-comparator
A quad comparator serves as the foundation for a frequency detector that is both faster and more cost-effective than more complex alternatives utilizing frequency-to-voltage converter chips. Positive feedback through a 5 MΩ resistor enables the circuit to detect changes as...