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FREE_RUNNING_COUNTER_DISPLAY

2016-12-04 03:00  
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FREE_RUNNING_COUNTER_DISPLAY
Atten-tion-getting circuit simply counts at predetermined rate while driving 3-digit display using 7-segment LEDs. Circuit uses two sections of 4011 CM0S quad NAND gate to generate pulses at rate controlled by 100-megohm pot. Pulses trigger 4026 counters connected as shown, with outputs a-g of each going to 7-segment LED dis-play. When all three displays reach 9, next pulse resets all to0 and count continues. Auxiliary circuit at upper right uses remaining sections of 4011 as flip-flop controlled by touch-plate switches; bridging gap between center and grounded plates with finger makes counter run. Bridging other gap resets counter to 0 and holds it there. If reset is not used, connect input pins 8, 9, 12, and 13 of unused gates to pin 14. -J. A. Sandler, 9 Easy to Build Projects under $9, Mod-em Electronics, July 1978, p 53-56.