Non-Contact AC Voltage Sensor Using LM358

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In this tutorial, we are making a useful project on a non-contact AC voltage sensor circuit using LM358. LM358 is a dual op-amp IC, it has two operational amplifiers built on a single chip. The circuit is simple, inexpensive, and only uses a few components like LM358A IC, a 4-inch antenna, LED, resistors, a variable resistor, and a battery. Since there are two op-amps in the IC that we are using therefore we don’t need many components to make the circuit work. This circuit is easy, beginner-friendly, and performs accurately.

The purpose of this circuit is to sense AC voltage in AC sockets or wires without making any contact or using a multimeter or any other device that needs to make direct contact with the main supply.

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Hardware Components

The following components are required to make AC Voltage Sensor Circuit

S.no	Component	Value	Qty
1.	Battery	4.5-12V	1
2.	IC	LM358A	1
3.	Antenna	4-inches	1
4.	LED	–	1
5.	Resistor	470KΩ, 470Ω	1, 1
6.	Variable resistor	1MΩ	1

LM358 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of LM358

AC Voltage Sensor Circuit

Working Explanation

This circuit can be operated on low voltage like 3V DC but an LED requires a minimum of 3.6 volts DC to operate for bright light due to which we are operating this circuit at 4.5V DC. An antenna will detect the AC voltage and sends a signal to the op-amp IC. this IC will amplify the output and activates the LED. The sensitivity of this circuit can be adjusted by the 1M variable resistor.

The power consumption of this circuit is quite low and when its in standby mode it only takes around 450µA. because of the low consumption of the circuit, the batteries will last longer. This makes the circuit ideal to use with small watch batteries or lithium coin size batteries, and with these batteries, the whole circuit can be fitted in a very small enclosure and can be carried around easily.