jumbo clock

elektor electronics december 1985 This digital clock makes use of the giant displays published in the July Et August 1985 issue of Elektor Electronics. It has a face of 720 mm wide by 280 mm high, which makes it readable at distances of up to 100 m. The display alternately shows the time and the ambient temperature. 1111771317 by A Sevriens The circuit diagram in Fig. 1 shows that the clock is designed around well-tried ICs. The clocking frequency is derived from the mains: T1 is provided with part of the sec- ondary voltage of 7"ri and converts this into a suitable rectangular signal. Low-pass filter R1-C9 and monostable /C21 ensure a noise- free 50 Hz signal. This signal is divided by 6 in /C4, then by 5 and 10 in /C5, and finally by 10 in IC6. The signal at pin 12 of IC6 is, therefore, 1/60 Hz, which is 1 pulse per minute. Circuit /C7 functions as a frequency con- verter: signals of 8"/3 Hz, 12/3 Hz, and 1/60 Hz are applied to its D4, D2, and Do inputs respectively. When 53 is ...