Report Radiation Levels Over MQTT with the IoT Geiger Counter v3.1

Using a Geiger-Müller tube as the basis of a DIY Geiger counter is not a new idea. But, surprisingly, very few of the existing projects have a built-in Wi-Fi radio to communicate counts. The IoT Geiger Counter, now in its third version, from g3gg0, adds an ESP32 to a counter design to send radiation and other environmental measurements to an MQTT broker.

An SBM-20 style G-M tube dominates the IoT Geiger Counter's circuit board. The tube's length comes out to about 105 millimeters. Because of this tube, the device is unmistakable as a Geiger counter. However, some WS2812 RGB LEDs literally add a bit of flash to the device. Their color indicates the counter's state. For example, it is green while idle, white flashes when counting, and red when you are going to have a bad day.

An ESP32-PICO-D4 module powers the counter. The popular microcontroller has two obvious and one not-so-common function. First, the ESP32 communicates with an MQTT broker over Wi-Fi. In this case, g3gg0 uses Grafana to display graphs of the captured data. The other obvious function of the ESP32 is counting the pulses from the G-M tube.

SBM-20 tubes need 400 volts for operation. The non-obvious function of the microcontroller is acting as a controller in a boost circuit to generate the required high-voltage (HV). It outputs a PWM signal to excite the inductor and uses a voltage divider to drop the HV down to the 1.1 volt range the ESP32 can handle.

Initially, g3gg0 attempted to use surface mount parts for the entire design. However, the boost converted needed 10 milliHeneries to achieve a stable 400 volts. And unfortunately, the equivalent series resistance (ESR) of surface mount inductors was too high. So, the design now relies on a through-hole inductor.

Not only does the IoT Geiger Counter measure radiation, but it also has two other environmental sensors. A CCS811 volatile organic compound sensor monitors VOCs. And a BME280 measures temperature and humidity. In addition to the RGB LEDs, there is a 5.83 inch electrophoretic display (EPD). These are also known as E-Paper. This display shows this sensor data.

You can build an IoT Geiger Counter using this blog/tutorial from g3gg0. There are instructions and options for each of the blocks. It details a few bugs, including an organic bug that caused a high-voltage breakdown. (So, is this also an IoT bug zapper?). All design files are available from the links at the end of the post.