LOW_COST_TIMER

Published:2009/7/14 5:16:00 Author:May | From:SeekIC

Want a simple timer at practically no cost? Depending on what parts you have, you might be able to build this circuit for less than a dollar. When S1 is closed, C1 begins to charge through R1 toward the 9-V supply. When the voltage at the input of the buffer, pin 3, reaches about 70 percent of the supply voltage, the output switches high for an 0N-time delay function. As long as S1 remains closed, the circuit will maintain the high output at pin 2. Opening S1 resets the timer by allowing C1 to discharge through D1 and R2.



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