LCD-LED Display

# Random Flashing LED Schematic Circuit Diagram

In recent years, the chapter ‘flashing lights’ in its many incarnations has already received plenty of attention in Elektor Electronics. Therefore, a newly presented flasher circuit has to have at least one special character in order to be considered for publication.

#### Random Flasher Circuit with Unique On/Off Rhythm

The circuit described here deviates significantly from an ‘ordinary’ flasher, setting itself apart by featuring a non-regular and random on/off rhythm. This distinctive characteristic opens the door for diverse applications, making it suitable for various games. Moreover, its potential as a ‘pseudo-alarm indicator’ can effectively deter potential burglars.

#### Complex Circuitry for Random Flasher Operation

Creating a random flasher entails a more intricate circuit design compared to standard versions. The schematic reveals the use of Schmitt-trigger IC3a to construct a conventional oscillator operating at a relatively low frequency. This oscillation signal serves as the clock for a shift register IC. By directing the outputs of the shift register through three inverting XOR gates (IC2a/b/c), the level changes at the output QH of the shift register adopt a quasi-random characteristic. This voltage variation is then applied to a high-efficiency LED (D1), completing the random flashing effect.

#### Optimized for 5 V Supply with Low Current Consumption

The circuit has been meticulously engineered for a power supply voltage of 5 V. When the LED is illuminated, the circuit consumes approximately 8 mA of current. This careful optimization ensures efficient operation within the specified voltage range, enhancing the circuit’s overall performance.

#### Understanding XOR Logic Gate and Nonlinear Functionality

The XOR logic gate, serving as a one-bit adder, combines two bits to produce a single-bit output. For instance, when adding binary 1 plus 1, the expected output is 10 (equivalent to 2 in decimal). In this context, the XOR gate calculates the trailing sum bit, while the preceding carry bit is computed using an AND gate. It’s worth noting that XOR’s distinctive nonlinear behavior, where it outputs 0 for identical inputs and 1 for different inputs, makes it impossible to represent using linear or two-layer networks. This inherent nonlinearity underscores XOR’s unique computational properties.

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