Simple Pressure Sensor Alarm Circuit

In this article it is an electronic gadget that can sense pressure changes.

Imagine a special plate that feels pressure like a doormat.

If someone steps on the plate pressure increases or air pressure changes in a machine, this circuit can detect it.

When the pressure gets higher than a set level, it sends a signal like a doorbell.

This signal then triggers an alarm or something else to let you know about the pressure change.

Circuit Working:

Parts List:

The simple pressure sensor alarms general purpose circuit is constructed using inexpensive readily available components.

Its operation is basic and easy to understand.

When powered by a 9V battery, the circuit activates the piezo sounder connected to IC1 emitting a short beep before entering an idle state.

Upon gently tapping the pressure sensor element a piezo ceramic wafer, an electric pulse triggers MOSFET T1 through the related components re enabling IC1.

Consequently, the piezo sounder beeps briefly as determined by the values of R3 and C2 in the circuit.

The piezo sounder can be swapped with a low current 6 to 9V electromagnetic or solid state relay to control external loads.

The specific values of components T1, R3 and C2 are not overly critical allowing for experimentation and adjustment to suit individual requirements.

Piezo sensors in wafer form are readily available from reputable hobby electronics component suppliers.

Formula:

The IC 555 operates as a one shot pulse generator while it is in monostable mode.

The following formula is used to calculate the output pulses duration.

Unchanging Mode Formula for IC 555 :

In monostable mode, the timing resistor R and timing capacitor C attached to the IC 555 determine the output pulse duration T.

Pulse Duration (T):

T = 1.1 × R × C

where,

• T is the duration of the output pulse in seconds.
• R is the resistance in ohms Ω.
• C is the capacitance in farads F.

It should be noted that the IC 555 internal mechanisms provide the constant 1.1.

Using the IC 555, this formula offers a simple method for designing a monostable circuit that allows for exact control over the length of the output pulse that is triggered by an external event, such as a pressure sensor.

How to Build:

Below mentioned are the steps to build a Simple Pressure Sensor Alarm Circuit:

• Connect pin 1 ground of IC1 to the negative supply of the breadboard.
• Connect pin 4 and pin 8 of IC1 to the positive supply of the breadboard
• Connect pin 2 of IC1 to pin 6 of IC1 together to the positive supply of the breadboard through a resistor R3 1M.
• Connect pin 6 of IC1 to pin 2 of IC1 through a capacitor C2 47nF and ground.
• Connect pin 3 of IC1 to ground through a BZ1 piezo buzzer.
• Connect the drain of the MOSFET T1 to the positive supply and connect the source of the MOSFET T1 to the negative supply through R3 1M resistor
• Connect the pressure sensor element piezo transducer between the gate of the MOSFET T1 and the negative supply.

Note:

• Once you have assembled the circuit, you can test it by applying pressure to the pressure sensor element.
• If everything is connected correctly the piezo sounder should emit a short beep.
• Adjust the values of R3 and C2 to control the duration of the beep as needed.

Conclusion:

A pressure sensor alarm circuit is a useful and relatively simple electronic circuit that can detect changes in pressure and trigger an alarm or other output.

It is commonly used in security systems, industrial automation and other applications where pressure changes need to be monitored and responded to.

References:

Circuit diagram of pressure sensors

Datasheet IC 555

Datasheet MOSFET BS170