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Up/Down Display LED Sequencer ProjectThis Up/Down Display LED Sequencer project uses a standard 4514 1 of 16 decoder to turn 16 LEDs ON and OFF in a sequential order. It uses a 4 bit binary input to select and turn ON one of the 16 outputs. A 40193 binary up/down counter IC2 supplies the binary input data to the 4514 decoder. Two gates of 4011 quad 2 input NAND gate IC1-c and IC1-d are connected in a low frequency astable oscillator clock circuit. The operating frequency is set by C2 and R20. The other 2 gates IC1-a and IC1-b are connected in a standard set and reset flip flop latching circuit. Switch S1 serves as the start switch and S2 as the stop switch. S3 selects IC2's up or down counting feature. Pressing S1 latches IC1-a's output high at pin 10, starting the oscillator by taking pin 2 of the IC1-c high. At the same time, the reset input of IC2, at pin 14 is latched low, enabling the IC to count up or down depending on the positon of switch S3. The LED1 to LED 16 turn ON and OFF in a sequential manner, one at a time as the clock operates. When the last LED turns ON and OFF, the sequence starts over and continues until the stop switch is activated. The schematic diagram of this project is as shown below.
With S3 in the UP position, the LED1 to LED16 starts the sequence and LED16 ends it. With S3 in the DOWN position, LED16 starts the sequence counting down to LED1.
Source : Extracted from Popular Electronics August 1996, By Charles D. Rakes. The specifications of
40193 Up/Down Display LED Sequencer
can be obtained from Fairchild Semiconductor website.
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