Introduction: Electrical Field Detector

Picture of Electrical Field Detector

This cool little project is the 1st circuit from ED Kit No.3. "Practical Devices". It is an Electrical Field Detector. One of my favorite breadboard gizmos because it is so simple in design, low cost and yet very useful. It can detect live wiring, switches, dormant power in TV's, Microwaves, Refrigerators etc in your house. Useful if your not sure if wiring or a household appliance has live power running through it or not.

When you power it on using the temporary push button the Green LED will come on, indicating that the circuit is running. As you approach an electrical field coming from live wiring or an appliance the Red LED will then start flashing, warning you the wire or device is alive!

It uses a CD4017 IC and two resistors. The sensitive timer pin on the IC is used to detect the electrical field of a nearby device with the help of a 10 cm 'probe wire'. Which is a standard 22 AWG 4.0" solid core breadboard jumper wire.

To build this circuit you will need the following parts and components:


1 x 400 point breadboard

1 x tactile push button

1 x 1k resistor 1/4W ( Brown / Black / Red / Gold)

1 x 470 ohm resistor 1/4W ( Yellow / Violet / Brown / Gold )

1 x 5mm Red LED

1 x 5mm Green LED

1 x CD4017BE I.C.

1 x 9 volt battery clip

(extra for looks) 1 x 2 point wire terminal for your battery clip

Breadboard jumper wiring:

1 x 0.2" red wire

1 x 0.4" yellow wire

5 x 0.6" blue wires

1 x 2.0" red wire

1 x 3.0" orange wire

1 x 4.0" yellow wire (probe)

Power Source:

1 x standard 9 volt battery

If you can't source these components our kit is available here:

Kit No 3 on Ebay

There is also a video of this project working at the end of this instructable.

Step 1: Push Button & I.C.

Picture of Push Button & I.C.

Place your CD 4017 IC onto the breadboard into sockets: F10 - F17 / E 10 - E 17.

Add the tactile push button to sockets: F6, F8 / E6, E8.

Step 2: Wire the Bus Lines

Picture of Wire the Bus Lines

Next wire the bus lines that will provide power to the circuit.

Place 1 x 2.0" red wire into positive power slots: W1 and Y1. Then 1 x 3.0" orange wire into: X1 and Z1.

Step 3: Add the Circuit Wiring

Picture of Add the Circuit Wiring

Place the following jumper wires into the breadboard:

(A) 1 x 0.2" red wire into: G8, G10

(B) 1 x 0.4" yellow wire into: A6, W7.

(C) 5 x 0.6" blue wires into the following slots: Z5, H4 / Z13, H11 / Z15, H13 / Z24, H22 and D17, X19.

Step 4: Add the Resistors

Picture of Add the Resistors

Time to add the two resistors to the circuit.

(A) Insert the 1k ohm resistor (Brown / Black / Red / Gold) into: J5, J8.

(B) Insert the 470 ohm resistor (Yellow / Violet / Brown / Gold) into: J15, J21.

Step 5: Insert the LED's

Picture of Insert the LED's

Insert the LEDs into your circuit.

Place the Green LED into G4, G5. (G5 is the longest leg which is called the Anode ). The Green LED is the 'Power On' light for this circuit.

Place the Red LED into G21, G22. (G21 is the Anode). The Red LED is the 'Alert' light to tell you the probe has detected an electrical field. It will flash continuously while you are in the electrical field and stop once you move away from it.

Step 6: Connect the Probe Wire and Power Wires

Picture of Connect the Probe Wire and Power Wires

Time to connect the 1 x 4.0" yellow probe wire into slot J12.

Don't use a flexible wire (nicknamed spaghetti by some) for the probe, as that would mean you would have to hold it in your hand. Your body's own electrical charge can sometimes be detected by this gizmo, that's why we use a solid core wire for the probe so that it can 'stand alone' without interference.

Last, add your battery clip wires to Bus Lines: W31 (red) and X31 (black). Connect a 9 volt battery. Make sure it is fully charged. A used or depleted battery will not work correctly.

Step 7: TEST the Device

Time to give it a test.

Once you have connected your battery give it a test and press the button. If it is all wired correctly the Green LED should come on. If not, check your wiring again or battery.

Walk around your home with the probe wire out in front of you and hold the battery behind the device. Try going near a power socket, extension cable wires, light switch, TV, computer screen, microwave, refrigerator etc and watch that red LED start firing away! Have fun. Be safe.


Electric Dreams Co.

Kaohsiung. Taiwan.

Face Book Link

Online Store

Ebay Store


pj200 (author)2017-02-09

Will Ic cd4017 work instead of cd4017be?

Thanks, and great project.

Rocky Chen (author)pj2002017-02-09

Hi. There shouldn't be a problem using another CD4017. Although the difference may be in the power requirement. The CD 4017 BE runs on 3 to 15 volts. (A 9 volt battery is used in this one described) The BE I use is a standard 4017 made by Texas Instruments. Yours may be of another manufacturer. If so the voltage requirement could be different. It may be between 2 to 6 volts. To be safe, 1st use a 3 volt power supply to test it. (2 x AA 1.5v).

About This Instructable




Bio: Rocky is a circuit designer for Electric Dreams Co., Kaohsiung, Taiwan.
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