Learn more about VLF here
TO ORDER: Call 903-558-1007
Basic Lightning Sensor
Build your own lightning flash warning alarm

Excellent for experimenters who are interested in watching the weather electronically.

lightning sesor

Use this basic lightning sensor to detect approaching lightning strikes!

This basic lightning sensor monitors the VLF electromagnetic activity of approaching storms and can sound a buzzer, blink an LED lamp, or activate other devices when it detects lightning.


  • Detects from all directions. No need to 'aim' it.
  • Detection range is adjustable easily by mounting height:
  • Range up to 10 miles when mounted 5 feet above ground.
  • Up to 30 miles range when mounted 10 feet above ground.
  • Up to 60 miles range when mounted 15 feet above ground.
  • Single "Beep" indicates distant lightning.
  • Several beeps in a second indicates closer lightning.
  • Nearly steady alarm indicates severe lightning storm.
  • Buzzer sold separately, below.
  • Draws no battery power while on standby. Works like a switch that turns "ON" when lightning is sensed.
  • Switches ON pass-thru current briefly for half a second for each lightning flash detected.
  • If powered by a 9-volt battery more than 2 years of standby operation.
  • Strong thunderstorms having intense lightning will cause a loud steady alarm to sound.
  • Detects VLF 3 KHz - 30 KHz for stable operation day and night.
  • Simple 2 wire connection to a 9-volt battery and a buzzer or LED lamp.
  • Rugged: Solid design resists dropping or vibrations.
  • Easy 2 wire connection: Output Red = (+), Black = (-).
  • You can use inexpensive "telephone cable" (available at LOWE's, or any hardware store) for outdoor connections.

    It is overload protected and reverse current protected, so you can't burn it out if experimenting with alarm circuits powered at 9 volts.

    Part # LSU-101 is $ 29.95 + $ 15.00 s/h. Ships via flat-rate Priority US Mail.

    Support Parts:

    You can purchase these parts or supply your own from your 'junk box'.

    Part # Buzzer1 $ 5.00. Beeps each lightning flash.

    Part # LED1Yellow $ 2.00 (supplied with dropping resistor if to be used without buzzer)

    9V battery snap connector $ 1.50

    TIP-120 NPN power transistor (makes the alarm super loud!) $ 3.00

    U-Mounting clamp: Available at any hardware store.

    Lightning Sensor Tester:

    Use this tester to check alarm operation. Simply shake it near the lightning sensor.

    Lightning Sensor Tester $ 10.00


    Save and refer to these online instructions.

    Wire the unit as shown above.

    The sensor module should be mounted on a 10-foot tall pole away from power lines, phone lines, and trees.

    Do not mount the sensor indoors, or in your attic, building materials may block the VLF radio waves.

    The sensor tip should not be higher than 20 feet above ground. If the sensor is too high then extreme range will result in detecting storms outside your area!

    Any two wire cable can run back indoors to your 9-volt battery alarm circuit.

    Connect a ground wire to the black wire on the sensor and connect to a ground rod (a 3 foot long piece of copper pipe) driven in the ground next to the mounting pole.

    When power is first turned ON, the alarm will sound for about 1 second.

    The lightning sensor module draws less power on standby than a wrist watch, so the battery will last about 2 years under normal use.

    If the range is too great, then lower the sensor.