Call bells, designed to draw attention, are commonly used in various environments such as offices, hospitals and residential care homes. Here, we explore a simple 12V LED dimmer circuit, incorporating an LM556 dual timer IC, which also functions as a call bell. The LM556 dual timer IC houses two 555 timers within a single 14-pin package. In this LM556 PWM-based LED dimmer circuit, the brightness of the LEDs is effortlessly controlled using a potentiometer. The author’s prototype is shown in Fig. 1.
Circuit and working
The circuit diagram of the LED strip dimmer and call bell, as shown in Fig. 2, is built around a 230V AC primary to 15V, 500mA secondary transformer (X1), a bridge rectifier (BR1), a 12V voltage regulator (LM7812, IC1), a dual timer (LM556, IC2), a MOSFET (IRFZ44, T1), a transistor (BC337, T2), an 8-ohm 0.5-watt speaker (LS1), and a few other components.
The 230V AC mains voltage is stepped down to 15V through stepdown transformer X1. This 15V secondary output of X1 is fed to bridge rectifier BR1. Capacitor C1 filters the voltage ripples, and the filtered output is supplied to the voltage regulator LM7812 (IC1). IC1 provides a 12V regulated DC output to power IC2. LED1 serves as a power-on indicator. Both timers of the dual timer LM556 (IC2A and IC2B) are configured in an astable multivibrator mode.
LED strip dimmer
この記事は Electronics For You の September 2024 版に掲載されています。
7 日間の Magzter GOLD 無料トライアルを開始して、何千もの厳選されたプレミアム ストーリー、9,000 以上の雑誌や新聞にアクセスしてください。
すでに購読者です ? サインイン
この記事は Electronics For You の September 2024 版に掲載されています。
7 日間の Magzter GOLD 無料トライアルを開始して、何千もの厳選されたプレミアム ストーリー、9,000 以上の雑誌や新聞にアクセスしてください。
すでに購読者です? サインイン
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