CASCADED_TIMER

Published:2009/7/12 21:34:00 Author:May | From:SeekIC

Two NE555 timers give sequential timing intervals for two separate loads.Time for U1 is set by R1 and C1, and for U2 by R2 and C2. Grounding pin 2 momentarily with switch starts timing. Once started, it cannot be retriggered. With pin 2 connected to reset input 4, both functions are obtained with one push of switch, lf reset function is not wanted, connect 4 to 8. When pin 3 of U1 goes low at end of timing interval, negative pulse generated by 0.001-μF capacitor and 27K resistor goes to pin 2 of U2 to trigger second timer. With 15-V supply, each timer can handle 200-mA load.-H. Vordenbaum, Automatic Reset Timer, Ham Radio, Oct. 1974, p 50-51.



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