IoT Geiger Counter with ESP32, OLED Display and Thingspeak Channel

• Low-power mode for use with batteries, OLED display and click sounds on, WiFi off
• WiFi mode for thingspeak data upload every minute, see https://thingspeak.com/channels/758223

Feel free to use this project as a base for your own projects AT YOUR OWN RISK!

Hardware

• Russian Geiger counter tube STS-6 at 400 V with ~5 MΩ series resistor
• High voltage circuit from ArnoR at mikrocontroller.net https://www.mikrocontroller.net/topic/380666, schematic https://www.mikrocontroller.net/attachment/273334/HystereseStepUpTLC555-2.png. Keep the high-voltage capacitor small to avoid dangerous charges!
• ~400 µs pulse generation using Geiger tube series resistors as voltage divider, high impedance input to darlington transistor and TLC 555 timer for rectangle pulse generation
• ESP32 board Wemos Lolin32
• OLED 128x64 with controller SH1106 at I2C
• Voltage supply from either USB or power supply or 3x 1.5V AAA batteries, circuit works from 3.0 V up to 5.0 V
• Pulse input is expected at GPIO 18 (high pulses with at least about 250 µs length)
• Switch for WiFi mode is expected at GPIO 4 (low=WiFi mode, high=low-power mode)
• OLED I2C bus is expected at GPIO 22 (SCK) and 21 (SDA)

Software

• Eclipse sloeber project using Arduino library, ESP-IDF for sleep functions and u8g2 for display output
• Low-power mode uses light sleep, a wake-up for each signal pulse change and a wake-up every 1000 ms to update pulse statistics and OLED. This results in about 90% sleep. Could be improved using deep sleep and ULP. However, light sleep is already quite good and much easier.
• WiFi mode uses no sleep and simple interrupts for pulse counting. Pulse statistics and OLED are updated every 1000 ms, data is sent to thingspeak every 60 s.
• Credentials (WiFi SSID, password, thingspeak channel key) are only declared in credentials.h and must be defined in a credentials.cpp