Last Updated on October 9, 2025
When ever I work with Transformers, Inductive circuit, I encounter a common problem, IS IT WORKING or NOT? I wonder if it’s possible to build a very simple Electromagnetic field (EMF) detector circuit using only few components (budget is my concern). After lot of browsing and searching I found numerous circuits again the same question rises will IT WORK? When I look into CD4017 CMOS decade counter based circuit, I thought to give a try. But that circuit requires little retouch hence that I came up with this simple EMF detector and electroscope circuit.
Here I have tested it with breadboard assembly and then made a PCB for that, You can use that PCB Gerber file to make one for you also. Happy circuit making!
Circuit Diagram
Components Required
- CD4017 Decade Count
- BC547 NPN transistor
- LED
- Resistors 150Ω, 270Ω
- Antenna wire, Normal 5 to 10 cm wire works fine
- Battery (5V–9V)
- Breadboard & connecting wires
Working Video
Construction & Working
Main element here is CD4017 CMOS decade counter IC and then Indicator LED. We know that this CMOS IC very sensitive to small voltage and current flow changes. Here I connected Antenna wire (normal hookup wire) to CLK input pin 14 and grounded CKEN, Reset pins. Then I take output from Q0 pin 3 to make it large enough to drive a LED I used a transistor switch made by BC547 NPN, Here the LED Anode is connected with Positive supply through 150Ω Resistor and Cathode is connected with collector terminal of Q1 BC547.
This LED either stays ON or OFF when there is NO EMF detected through Antenna wire and LED starts to BLINK Faster when the Antenna wire receives enough EMF. IC CD4017 receives impure clock through Antenna wire and counts fast from Q0 to Q9, It makes LED connected to Q0 blink. That’s it you know the EMF location.
Printed Circuit Board
Simple EMF Detector and Electroscope Circuit Gerber file.
Interactive Board Viewer
Note:-
Here the Antenna Wire plays important role, Too short = Less Sensitivity, Too long = picks up noise. Just try 5cm to 15cm and if it possible use 6X6 cm metal plate. This circuit works better near AC mains wiring and Active electronic Devices. If the LED stays ON continuously then reduce the length of Antenna wire.