Thunder Click Lightning Detector
1471-1115-ND / MIKROE-1444
AS3935-BQFT-ND / AS3935-BQFT
The MIKRO-1444 is an expansion board from MikroElektronika that is meant to help detect lightning. This is done by using the AS3935-BQFT lightning sensor from AMS. This device communicates using I2C and SPI and also allows for several threshold settings. This device has the ability to provide an estimate to the head of a storm by calculating how far away a lightning strike is. The device has a range of 40km and can estimate up to 1km away from where the lightning strike occurred. There is even an embedded algorithm that helps to reject unwarranted man made noise. This device is great for weather stations that record lightning strikes, or any application that needs to monitor weather. Since this has a range of 40km it can effectively give a safe warning to people that a storm with lightning is coming.
There are several controllable features of this device. The user will have the ability to control the noise floor level. There is an internal noise floor generator that can be set to different levels. This is helpful because it can be set so that if the noise level is too high and interrupt can be sent to inform an MCU that the AS3935 cannot operate properly. The noise floor shares an address with the watchdog and is named NF_LEV. Figure 1 shows the settings for the noise floor threshold.
Figure 1 – Settings for the noise floor threshold
Another controllable feature is the “Analog Front-end” (AFE) that amplifies and demodulates the received signal. This will basically have two modes of operation, indoor and outdoor. The default setting is for indoor use, but the device can be changed to have less gain if being used outside. Figure 2 shows the AFE settings for indoor and outdoor use.
Figure 2 – Settings for AFE
An additional value that can be changed is the “Watchdog” threshold. This “monitors the output of the AFE and alerts the integrated lightning algorithm block in the event of an incoming signal.” This algorithm has the capability of providing an MCU with an estimated distance to the head of the storm. This can be set in the register WDTH REGX01[3:0] which shares an address with the NF_LEV. Figure 2 is from the detailed register map and shows the WDTH and NF_LEV address and names. The address is 0x01 and the names and default values of 010 and 0001 can be seen.
Figure 3 – Address and names for Watchdog and Noise Floor Level
Spike rejection is another value that can be changed in the AS3935. This is used to reject impulse signals picked up by the antenna. This is found in the register REG0x02[3:0], larger values will correspond to better disturber rejection.
The MIKROE-1444 from MikroElektronika was used for this project. It was hooked up to an Arduino Pro Mini 3.3v. The code that was used was taken from GitHub using the ThunderAndLightning example from Eva Schindling, there is a link below. This project used a different evaluation board than the MIKROE-1444 but it was still possible to convert the project over to an Arduino Pro Mini 3.3v. Table 1 illustrates the pinout that was used.
Arduino Pro Mini 3.3v
SI (Internally grounded – no need to connect)
Table 1 – Pinout for MIKROE-1444 using Arduino Pro Mini 3.3v
Figure 4 shows a schematic of the Thunder Click board. As previously mentioned, SI is internally grounded on the Thunder Click board.
Figure 4 – Schematic of Thunder Click (MIKROE-1444)
There is also a page on LibStock that has some different compilers and example code if a PIC MCU is desired rather than an ARM MCU. A link to this can be found below.
LibStock example: https://libstock.mikroe.com/projects/view/750/thunder-click-example