Simple Mains AC Transients Indicator Circuit

Imagine you have a device to monitor the ups and downs in your homes electricity.

This circuit is like that device, but specifically for sudden voltage spikes.

These spikes can be caused by things like lightning, appliances turning on or changes in power usage.

The circuit has a sensor that constantly checks the voltage.

If the voltage jumps up higher than usual the circuit triggers an alarm, like a buzzer or light to let you know there was a spike.

Circuit Working:

Parts List:

Instant voltage fluctuations are a common occurrence in power lines especially in areas with heavy machinery.

Inductive loads and high power transformers can generate transients and spikes in the mains lines.

These voltage fluctuations pose a risk to SMPS based power supplies and microcontrollers.

Here is a simple circuit that continuously monitors the power lines and produces a beep for each voltage fluctuation.

The circuit alerts you to potential voltage drops and spikes in the power supply connected to microcontrollers and SMPS based electronic devices.

Even a minor voltage spike as low as 10V in the mains can lead to operational errors and data loss in such devices.

SMPS power supplies are particularly susceptible to these voltage changes in the mains.

The circuit utilizes the popular timer IC 555, configured as a short duration monostable with timing elements R1 and C2.

Power for the circuit is supplied by a 0 to 12V step down transformer, with a bridge rectifier D1 to D4 and smoothing capacitor C1.

Any variation in the primary voltage of the transformer will be reflected as a corresponding change in its secondary voltage.

The trigger pin 2 of IC1 is connected to a potential divider consisting of R2 and VR.

The triggering threshold voltage of IC1 is set by VR to keep the voltage level at pin 2 slightly higher than the triggering threshold.

This ensures that the output of IC1 remains low when the mains voltage is normal.

If the voltage drops, the voltage at pin 2 of IC1 decreases triggering the IC.

The buzzer beeps to indicate the presence of transients.

If the beeps occur frequently it is advisable to unplug the electronic devices to protect them.

Formula:

A simple circuit called the Mains AC Transients Indicator Circuit finds and displays transients or spikes in the AC mains voltage.

The following formula determines the output pulse width T of the 555 IC in monostable mode:

Mode Monostable of 555 IC:

T = 1.1× R × C

where,

• R is the resistor that connects the 555 IC discharge pin 7 to threshold pin 6
• The timing capacitor, denoted as C is linked to the discharge pin 7 and ground.

Using simple electrical components, this circuit offers a basic foundation for identifying and detecting AC main transients.

Adapt component combinations and values to your desired transient sensitivity and unique needs.

How to Build:

Below mentioned are the steps to build a Simple Mains AC Transients Indicator Circuit:

Power Supply:

• Connect the positive terminal of the bridge rectifier to the positive rail of the breadboard or PCB, and the negative terminal to the ground.

IC Connections:

• Place the 555 IC1 on the PCB.
• Connect pin 8 to the positive rail and pin 1 to the ground.

Timing Components:

• Connect R1 100k between pin 7 and pin 6 of IC1.
• Connect C2 10uF between pin 6 and ground.

Threshold Voltage Adjustment:

• Connect a resistor divider using R2 10k and VR 5k preset between +12V and ground.
• Connect the junction of R2 and VR to pin 2 of IC1.
• This adjusts the threshold voltage for triggering.

Buzzer Connection:

• Connect the positive terminal of the buzzer to pin 3 of IC1, and the negative terminal to ground ground.

Power Supply for IC:

• Connect a 1000uF capacitor C1 between +12V and ground to provide smooth power to the IC.

Transformer Connection:

• Connect the step down transformers secondary to the mains power lines.
• Connect the primary side to the mains power supply.

Testing:

• Power on the circuit.
• Adjust VR until the buzzer beeps.
• The circuit will beep whenever there is a voltage fluctuation in the mains power lines.

Note:

• Exercise caution when working with mains voltage.
• If you are not familiar with working with high voltage consider seeking assistance from someone experienced.

Conclusion:

To conclude, a Mains AC Transients Indicator Circuit is a valuable tool for detecting and indicating voltage spikes or transients in the mains AC power supply.

It helps protect sensitive electronic equipment from damage and ensures smooth operation by alerting users to potential issues.

Integrating this circuit into electronic devices can enhance their reliability and lifespan.

References:

What are AC and DC transients, rather do we even classify transients that way?