Simple Delay Timer Circuit

Posted on Feb 5, 2014

Without the specified delay the circuit could malfunction or even get damaged. A capacitor, which is the crucial part of the circuit gets the specific position in the circuit, we can see thatit`s been placed at the other end of the base resistor and not directly to the base of the transistor. On depressing the button momentarily, a positive voltage from the supply line enters the base

Simple Delay Timer Circuit
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resistor and switches ON the transistor and subsequently the LED. On releasing the push button, though the power to the base gets disconnected, the transistor continues to conduct with the aid of the stored energy in the capacitor which now starts discharging its stored charge via the transistor. Along with the capacitor, the value of the base resistor also plays an important role in determining the timing for which the transistor remains switched ON after the push button is released. The addition of another transistor stage increases the sensitivity of the circuit, which enables the use of larger values of the timing resistor thereby enhancing the time delay range of the circuit. The above circuit can be modified to produce a two step sequential delay generator. This circuit was requested by one of the avid readers of this blog, Mr. Marco. "I am looking to build a circuit that would control an output relay. This would be done in 12V and the sequence will be initiated by a manual switch. I will need an adjustable time delay (possibly displayed time) after the switch is released, then the output would go on for an adjustable time (also possibly displayed) before shutting off. The sequence would not restart until the button was pressed and released again. The time after the button release would be from 250 milliseconds to 5 seconds. The "on" time for the output to turn on the relay would be from 500 milliseconds to 30...

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