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Description

The dual-direction counter employs a 4-bit binary increment/decrement counter (CD4516) and two “1 of 8 line decoders” (74HC138 or 74HCT138) to produce the recognizable “Night Rider” display. A Schmitt Trigger oscillator furnishes the timing signal for the counter, and its frequency can be modified utilizing the 500K potentiometer. Two supplemental Schmitt Trigger inverters are utilized as a SET/RESET flip-flop, enabling control over the counting direction – either upwards or downwards. It is crucial to utilize the 74HC14 and not the 74HCT14, as the 74HCT14 may exhibit non-operational behavior due to its lower TTL input trigger level. Upon reaching the maximum count value (1111), the low output at pin 7 activates the latch, subsequently causing the UP/DOWN input to the counter to become inactive, thereby initiating the counter’s decrementing operation. When the minimum count value (0000) is achieved, the latch is reset (high), permitting the counter to resume incrementing with the next rising clock pulse. The three lowest counter bits (Q0, Q1, Q2) are interconnected with both decoders in parallel, while the highest bit, Q3, is implemented to select the appropriate decoder.

Integrated Circuit Details

The CD4516 is a versatile 4-bit binary counter IC. This device consists of two up-down counters, each capable of counting from 0 to 15. It utilizes static CMOS technology and is ideal for applications requiring precise counting.

Integrated Circuit Details

The 74HC138 is a versatile 8-to-1 line decoder IC. It converts an 8-bit binary input into one active output line. This IC is commonly used in digital logic circuits and displays.

Integrated Circuit Details

The 74HC14 is a high-speed CMOS inverting gate. This IC provides a reliable and fast inversion of input signals, and it is widely employed in digital circuits for signal manipulation.

Circuit diagram