The "on" time for the output to turn on the relay would be from 500 milliseconds to 30 seconds.
The time after the button release would be from 250 milliseconds to 5 seconds. The sequence would not restart until the button was pressed and released again. 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.
Phase shifter vs simple delay manual#
This would be done in 12V and the sequence will be initiated by a manual switch. "I am looking to build a circuit that would control an output relay. The following circuit was requested by Fastshack3 Delay Timer with Relay This circuit was requested by one of the avid readers of this blog, Mr.Marco.Ī simple delay OFF alarm circuit is shown in the following diagram. The above circuit can be modified to produce a two step sequential delay generator. The solution to the above problem is provided in the following schematic: Two Step Sequential Timer Is there any way to take a long pulse into a circuit and send a much shorter pulse out? I have a situation where I have a pulse of 12V that lasts about 4 seconds (from a rotary switch being turned by a slow motor) but I only want about half a second pulse (to trigger a mechanical bell/chime). Glen (one of the dedicated readers of this blog): The following circuit shows how the associated push button may be rendered inactive as soon as it's pressed and while the delay timer is in the activated state.ĭuring this time any further pressing of the push button has no impact on the timer as long as the output is active or until the timer has finished its delay operation. The above delay OFF effect without a push button can be further improved by using two NPN transistor, and by using the capacitor across base/ground of the left NPN If the above design is intended to be used without a push button, the same may be implemented as indicated in the following diagram: The above could be further modified with a self contained power transformerless power supply as shown below: Without a Push-Button 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. However the circuit using just one transistor will be able to produce time delays which may range only for a few seconds.īy adding one more transistor stage (next figure) the above time delay range can be increased significantly. Te value of the capacitor determines the time delay or for how long the transistor stays in the conducting mode.Īlong 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 LED also stays switched ON until the capacitor gets fully discharged. 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. However in the course of the above action, the capacitor also gets charged fully. On depressing the button momentarily, a positive voltage from the supply line enters the base resistor and switches ON the transistor and subsequently the LED. The transistor has been provided with the usual base resistor for the current limiting functions.Ī LED which is used here just indication purposes behaves like the collector load of the circuit.Ī capacitor, which is the crucial part of the circuit gets the specific position in the circuit, we can see that it's been placed at the other end of the base resistor and not directly to the base of the transistor.Ī push button is used to initiate the circuit. The first circuit diagram shows how a transistors and a few other passive components may be connected for acquiring the intended delay timing outputs.
Using a Single Transistor and Push Button You may also want to read about IC 555 based delay timers. Let's analyze the various configurations in details. Without the specified delay the circuit could malfunction or even get damaged. In many electronic circuit applications a delay of a few seconds or minutes becomes a crucial requirement for ensuring correct operation of the circuit.
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