A weight sensor, or load cell, uses strain gauges bonded to a bending beam. Their electrical resistance changes minutely when force is applied, stretching or compressing them. These gauges are arranged in a Wheatstone bridge circuit, producing a small voltage change. This signal is amplified and converted to a digital reading by an integrated circuit like the HX711, which a microcontroller can then interpret as a weight measurement.
Automatic hallway lighting is designed to activate lights temporarily when a person is detected, and natural light is insufficient. A pyroelectric motion sensor or sound detection is used for presence detection. The BISS0001 chip controls the lighting, and components like resistors and capacitors set the light's activation duration. The circuit is powered by AC, using a full-wave bridge rectifier and solid-state relay to manage the light.
Overheating in electronics can result from factors like fan failure, degraded thermal paste, dust buildup, or blocked ventilation. To address this, devices use temperature monitoring systems that trigger alarms or disable functions when thresholds are exceeded. A demo circuit uses a 555 timer and LM358 comparator to simulate automatic overheating protection.
Flammable gas sensors, such as the MQ-5, are vital for detecting dangerous gases like propane, butane, and methane. These sensors use a sensitive semiconductor layer to react to gases, with components like a heating coil and gold electrodes ensuring accurate detection. They are critical in safety applications, including home gas detection and industrial use, offering early warnings of gas leaks and preventing explosions.
A sensitive amplifier with a filter is needed to process signals from ultrasonic or infrared sensors. The GL3274 IC, designed for infrared receivers, is used for this purpose. It operates at 4.7–5.3 VDC and features internal protection, band-pass and low-pass filters, and comparators. Replacing a photodiode with an ultrasonic receiver enables accurate distance measurement.
