Short to medium time power on delay ...

... with an operational amplifier. This is a circuit which delays for the time configured by the cap and the poti and then switches the output on. The output could switch an relais on to power up some devices. If you want to bridge a longer time increase the cap's size. I wouldn't increase the poti's size because the nearer you get to the OP's input resistance the more the timing gets inaccurate (nonelinear drift of delay over poti-position as an example). If you really want to increase the poti's size you need an OP with a higher input resistance. You can use a lower voltage too, but on more volts the circuit is more accurate. On my phone this circuit generates the loved "cannot find solution" when the configured delay is over, but in reality this circuit works pretty well.

published 11 years ago