Anticipating timer switches before you push the button

  EDN Design Idea   This Design Idea   offers a solution to the challenge of turning devices on or off in the past. In Figure 1, IC2 is a 555-type timer (preferably CMOS) connected as a monostable one-shot multivibrator. The pushbutton switch, S1, triggers IC2. You can replace S1 with a transistor or an optocoupler, for example. You can connect VOUT to a relay or a transistor, if needed. You might need to adjust the values of R4 and R5, depending on the output load and the characteristics of S1. The interval during which VOUT remains high is T=1.1RC2. …

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