In one of my previous videos I showed you how to make such a detector with the help of AS3935 sensor board which is specially designed for this purpose. This time I will show you how to make same such device, but now with homemade detector circuit based on cheap AM Receiver IC TA7642. 

This design is many times cheaper, its sensitivity is much higher, and Also the resistance to local disturbances as a various sparks from electrical devices is very high. The ingenious idea of using AM reciver IC as a detector is presented on page under the name "The Franzis thunderstorm warner". The basic Arduino code is taken from Ramser-elektro ,and I modified it by adding an active Buzzer and some other small changes.
     The device is relatively simple to build and contains several parts:
         - Detector board
         - Arduino Nano microcontroller
         - four LEDs for visual indication with resistors
         - active buzzer as audio indicator
         - and small galvanometer also for visual indication

   The detector works in the following way: The radio waves from the lightning are received, pre-amplified, demodulated and amplified by the TA7642. Then the output is routed to the analog input A0 of the Arduino. This results in a "voltage drop" in the voltage at the A0 Arduino input per lightning discharge. The more "voltage drops" at the analog input, the more discharges, the closer the thunderstorm.
    The sensitivity of the device as well as the resistance to disturbance can be changed in the following two lines of code:

    PWM_DutyCycle = (PWM_DutyCycle /3 ) * 2;  // PWM value is set to 2/3, for more sensivity 5/6 or 8/9

    if (Difference> = 15) {  // Would test 12 times there.

   The way the device works is: When starting, the voltage of the TA7642 is increased until a certain basic voltage is applied. This is indicated by turning on all the LEDs one by one and finally when all are turned off the device is ready for detection. We perform a thunder simulation with a piezo lighter. The device detects the spark from the piezo lighter at a distance of 1 meter and more. In real conditions, depending on the strength of the lightning, the range reaches up to hundred kilometers. Electrical discharge detection is indicated by a flashing white LED and a short beep from the piezo booster. There is also a small analog instrument whose arrow deflects with each lightning strike.
   If a certain number of electrical discharges occur per unit time, the green LED starts flashing and this is the first level of warning. This means that the storm is close to our region. If the discharges continue, the yellow LED starts flashing, which indicates the second level of warning, and the storm is gradually approaching. Finally, if the red LED flashes, a third level warning is activated, which means that our region is hit by a storm. By reducing the frequency of electrical discharges, the warning level is automatically reduced. 

    The device is installed in a suitable box made of PVC with a thickness of 5 mm, which is coated with colored wallpaper.