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CIRCUIT · NON CONTACT AC VOLTAGE DETECTOR

Non-Contact AC Voltage Detector Circuit Diagrams

Need a non-contact AC voltage detector circuit diagram? Browse these practical examples built with transistors, LEDs, and piezo buzzers—no direct electrical contact required. Each diagram is ready to use, modify, or rebuild from scratch.

4 EXAMPLES· UPDATED 2026-09-12
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ELECTRONICS

2-Transistor Non-Contact AC Voltage Detector with Piezo Buzzer

ELECTRONICS

Non-Contact AC Voltage Detector with LED and Buzzer

ELECTRONICS

Non-Contact AC Voltage Detector

ELECTRONICS

Single-Transistor Non-Contact AC Voltage Detector

ABOUT

About these examples.

Whether you're a hobbyist troubleshooting mains wiring, an electronics student prototyping a sensor, or an engineer designing a safety indicator, these circuits show how a simple antenna and amplification stage can detect live AC fields.

Pick an example below to open it in the editor, tweak component values, and generate your own schematic in seconds.

HOW TO

Make one yourself.

  1. 1

    Choose a baseline circuit

    Start from one of the non-contact detector examples or a blank circuit canvas.

  2. 2

    Add the sensing stage

    Place an antenna (often a copper trace or wire) and a high-impedance input transistor to pick up the AC field.

  3. 3

    Build the signal path

    Add amplification and output components—LED, buzzer, or both—so the detection is visible or audible.

  4. 4

    Simulate and verify

    Run a quick simulation to check that the circuit responds to a simulated AC field before building it physically.

  5. 5

    Export or share

    Download the circuit diagram as an image or share a live link for collaboration.

FAQ

Frequently asked questions

How does a non-contact AC voltage detector work?01
It uses a small antenna to capacitively couple with the electric field around a live AC wire. The tiny induced voltage is amplified by transistors or an op-amp to light an LED or sound a buzzer.
What components are typically needed?02
Common components include an antenna (copper trace or short wire), one or two NPN transistors, resistors, an LED, and optionally a piezo buzzer. Some designs add a capacitor for filtering.
Can I test these circuits before building them?03
Yes, ChatDiagram lets you simulate the circuit and adjust component values to verify the detection threshold and output behavior.
Are these circuits safe to use near mains voltage?04
The circuits themselves are low voltage and isolated, but always follow electrical safety practices when working near live AC wiring. The detector should never touch bare conductors.
Can I modify an existing diagram for higher sensitivity?05
Absolutely. Increase the gain by adding another transistor stage or adjust the input resistor to change sensitivity. The editor supports full schematic editing.
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