The 20-second period can be checked with wristwatches and the stopwatches on mobile phones, but these are not convenient to use while washing hands. This proposed circuit rings a buzzer for 20 seconds and switches on an LED for audio as well as visual indication (for those with hearing issues). The author's prototype is shown in Fig. 1.
The circuit for this alarm, shown in Fig. 2, comprises a 9V battery, 5V voltage regulator LM7805 (IC1), timer NE555 (IC2), relay driver ULN2003 (IC3), 5V SPDT relay (RL1), and a few other components.
Resistor R2 and capacitor C2 decide the time of monostable, which is around 20 seconds here. This output time period of IC2 at its pin 3 (monostable multivibrator built around NE555) can be calculated using following relationship:
T = 1.1RC
where R = R2 = 18k and C = C2 = 1000μF.
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Denne historien er fra January 2023-utgaven av Electronics For You.
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TRULY INNOVATIVE ELECTRONICS -INNOVATION UPDATES
Amongst numerous press releases of new products received by us, these are the ones we found worthy of the title Truly Innovative Electronics
Elastomer enhancing smart wearable performance
A high-tech, flexible wearable device made from the innovative elastomer material
Nanotechnology based noninvasive cancer diagnostics
Nanoflake sensors built from indium oxide with platinum and nickel detect changes in isoprene
Space communication with silent amplifiers
In the new communication system from researchers at Chalmers University of Technology, in Sweden, a weak optical signal (red) from the spacecraft's transmitter can be amplified noisefree when it encounters two so-called pump waves (blue and green) of different frequencies in a receiver on Earth.
Advancements in TOPCon solar cells
The structure and performance of tandem devices with highly passivated TOPCon bottom cells
Quantum leap in magnetism refines superconductors
Rice University physicists have uncovered key magnetic and electronic properties in kagome magnets, structures resembling basket-weaving patterns.
Sensor targets food antioxidants
A research team from Hunan City University and Xiangtan University in China has developed a sensor for detecting TBHQ, a food antioxidant used in oils and fats, addressing health concerns at high concentrations.
Data sensing with repurposed RFID tags
UC San Diego researchers have advanced passive data collection with a breakthrough in battery-free sensing.
Seal-inspired sensors to safeguard offshore wind farms
Schematic structure of the seal whisker-inspired flow sensors
Artificial nose identifies scents accurately
Artificial nose identifies scents accurately
