Voltage Relay Activated Circuit Advice Required

Thread Starter

Aodius Tan

Joined Jan 17, 2018
Hi all,

I would like to check if there's anyone able to help me out with a basic circuit design as shown in the image.

Basically, there is a door that is normally close where current should flow through hence not activating the alarm.

In the event that someone wants to pass through this door, the normally close circuit will then be open which will cause the buzzer to sound.

Therefore, a voltage relay is added into this circuit that will be normally open. It should only be close when a door entry switch is pressed and allow entry without causing the buzzer to sound.

However, there are some issues I may face whereby how long can the voltage relay last in a close circuit when my door entry switch will only be a ''one tap pressure''. This means that the voltage that trigger this voltage relay will not last longer than a specific duration.

How can I better manage this time frame of my voltage relay to ensure it will not goes back to normally open until my door is closed back?

As well as how can I connect my this door entry switch (that will send the voltage) to the normally open relay in the circuit that I drew.

My sincere apology for my lousy English and at the same time appreciate and thankful for all the help that I may get.



Joined Jan 29, 2010
hi AT,
Welcome to AAC.
The circuit diagram you posted is incomplete, it will not work as you expect.
You say when the door is Closed the 'Sensor' switch is Closed, when the door is opened the Sensor switch is Opened and a Buzzer sounds.?

You want to add a Door Entry switch, when pressed it disables the Buzzer, but you do not have control over the Entry button press duration.?



Joined Jan 4, 2017
Hi there, can you please clarify your question? The way I understand it, you either want:
  1. The door to open and the buzzer to sound continuously until it is closed or...
  2. The door opening triggers a buzzer for a set amount of time then turns off
I also assume you are not making this from scratch and you are modifying some existing circuit? In theory this should be easy to come up with a solution.


Joined Jan 29, 2010
hi AT,
This simple relay circuit will link across the Sensor switch.
When the Entry button is pressed the relay will operate and link the the Sensor contacts, the buzzer will not sound.
The time period the relay is energised for is set by the 10uF and 1 megohm resistor.[ let us know the required time period]
The Relay will require its own 6V DC supply.