PROGRAMMABLE_0_825_Hz_PULSES

Published:2009/7/14 5:13:00 Author:May | From:SeekIC

Inexpensive pulse generator is programmable in 0.4-Hz steps from 0 to 825 Hz, and can be modified to extend range to 200 kHz, Circuit uses 555 connected in astable mode, with timing resistor RA replaced by 11 sets of timing resistors and switching transistors. Inputs and outputs are TTL-compatible. When bit input is high (0), its associated transistor is turned off. When bit input is low (1), transistor is on, allowing C1 to charge. When more than one input is low, charging is through parallel combination of resistors. Width of output pulse T1 is constant over frequency range.-E. G. Laughlin, Inexpensive Pulse Generator Is Logic Programmable, EDN Magazine, Aug. 20, 1974, p 92.



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