Home Projects Oscillators and timers Digital Stopwatch 0-60sec Digital Stopwatch 0-60sec author: Koukos Konstantinos, Tsormpatzidis Dimitrios - Aristotle University of Thessaloniki Undergraduate students at Department of Electronics and Telecommunications - Physics Department Introduction       By using the same circuit of the Digital Stopwatch 0-99sec , we can add an AND gate, and transform the 0 – 99sec stopwatch to a 0 – 60sec stopwatch.         We must find a way to control the RESET function of the BCD counter, which is responsible for the counting of the seconds. As we studied above, the circuit resets when we have 99 to 100, that is 1001 1001 à 0001 0000 0000. To make a transformation successfully we must force the pulse from 59 to 60 0011 1001 à 0100 0000 on the output of the BCD counter.      By placing the AND gate, with its inputs on the Q1 and Q2 of the BCD counter of the decades, we make sure that when the gate closes, the RST input of the BCD counter will be set to logical “1”, which on its turn, will force the circuit to start over. The transformed circuit appears in picture 2. Search Site | Advertising | Contact Us Elektrotekno.com | Free Schematics Search Engine | Electronic Kits p.footer { margin: -24px 0px 8px 0px; color:#F4DE34; line-height:16px; font-family:Arial; font-size:12px; text-align:center; } Electronics-lab.com - 2002-2015 Any logo, trademark and project represented here are property of their owner