Most of us are held up with our busy life, be it at office or at home. Often due to our workload and carelessness we tend to forget to close the doors in our office or at home. This habit can lead to robbery or sometimes pets/ animals will sneak through the door looking for food. Here is a simple door open alarm circuit that will raise an alarm whenever a door is left open. The alarm will only cease when door is closed. This alert system will remind us to close the door.
COMPONENTS REQUIRED:
- 555 IC
- Resistors- 2.2k,10k
- Capacitors – 1micro, 0.01 micro, 100micro
- 2 pin headers
WORKING OF DOOR OPEN ALAM CIRCUIT:
door-open-alarm-circuit-security-system
This circuit uses 555 IC as an astable multivibrator ( read about working of IC 555 here ). This generates square wave pulse as output. This circuit uses magnetic reed switch which acts like a simple switch to establish connection. This reed switch closes when a magnet is enters its proximity. This magnet attracts the throw of the switch and closes it. When magnet is moved away from the switch reed opens up breaking the circuit connection.
reed-switch-magnet-placement
The above image shows the position you can install your Reed switch and magnet. In this position the magnet will influence the reed switch when it is closed. When the door is opened the magnet moves away breaking the reed switch connection.
In a of 555 IC pin 4 or reset is used to switch the 555 operation to active or inactive state. When the pin 4 is connected to high state 555 gets activated and when it is connected to low state 555 gets deactivated. Here reed switch is used with reset pin to set 555 operation. Let’s consider the below two cases to understand this circuit working.
Case 1: When the door is closed
According to our need when the door is closed alarm should remain inactive. When the door is closed the “Reed switch” will be attracted by the magnet present at the door. Due to this magnetic field, Reed switch closes its connection and the reset pin will be connected to ground via reed switch. This will set the 555 IC to inactive state. There will be no output from 555 hence the speaker will not produce any sound.
Case 2: When the door is opened
When the door is opened the alarm should turn ON. Opening the door will move the the magnetic field away from the reed switch. This breaks the reed switch connection. This pulls the the reset pin of 555 IC high using pull up resistor R1. This forces the 555 IC to active state thus producing square wave pulse as output. This square wave drives the speaker ON, thus raising the alarm.
NOTE:
- The above suggested reed switch and magnet position is for your reference. You can choose any feasible position to install but ensure the magnet is in a proximity to influence the reed switch when the door is closed.
- You can use a low watt speaker if you want the alarm to be low subtle. The speaker shown in the circuit can considerably produce very high volume alarm which can be annoying.
Try this circuit out and post your queries and feedback in the comments section below. Visit our Circuits library page for more circuits and projects.
your door alarm circuit is not usable
and incomplete, check your posts before
displaying them.
I think there is a mistake. You need to connect pin 8 of 555 Timer to Vcc.
It is helpful to us so thank you
Will I need the pin headers if I am going to use q bread board ..and concerning the pin headers both are male right?
Seif,
Pin headers are not mandatory you can use any other means of connectors that’s convenient to your setup. Yes both are male headers.