GK-WiFi Add-on Kit

The GK-WiFi Kit:

The GK-WiFi kit is a good way to get your Geiger kit readings to web sites on the internet. The GK-WiFi attaches to any of the counter kits here - GK-B5, GK-Mini, and GK-Plus. The software provides support to send your data to Radmon.org, ThingSpeak and MQTT brokers. (These sites are described below.)

The kit uses an ESP8266 SOC for WiFi connectivity and processing. The board connects directly into your kit's FTDI port and reads the serial data (CPM, Dose, Vcc). coming from the kit. It then connects via WiFi to the sites you specify in the software and sends those readings. Three status LEDs show network down, data available, and send OK.

The GK-WiFi kit was also designed so that it can serve as a development platform for the ESP8266. A carrier board is used to hold the ESP8266 for ease of replacement, all common I/O pins are broken out and the LEDs can be disabled. This chip is a lot of fun to work with with using the Arduino IDE add-on package.

The software also supports an optional BME280 sensor that captures temperature, humidity, and barometric pressure and sends those in addition to Geiger readings.


An I2C OLED display can also be added. The software supports it to display the connection status, or it can be used for other developments.

The GK-WiFi is only 1.85” x 1.40” (~4.7 x 3.6 cm) and the kit includes everything you need hardware-wise to use it.

Please Note: This kit requires that you be prepared to upload your modified sketch to the ESP8266 with the Arduino IDE after you add your network and site credentials. Step by step instructions for this are provided in the Build Instructions for doing this, but I'd hesitate to recommend this kit to those with no programming experience.

For more detailed information, refer to the GK-WiFi Build Instructions below.

Purchasing the GK-WiFi kit:

The kit includes the ESP8266 and carrier board, and all parts needed to make the board shown above. All GK kit types are supported - GK-B5, GK-Plus, and GKmini. The DHT22 sensor, and I2C OLED options are not supplied.

Kits are available for purchase on the "Buy the Kit" page.

GK-WiFi Build Instructions:

The Build Instructions for the current v1.5 board with v2.0 software are here.

(Previous versions of the GK-WiFi Build Instructions may be found on the Archive Page. )

About Radmon.org, ThingSpeak, and MQTT:

Radmon.org is dedicated to radiation monitoring and has attracted a good group of users at this point. It uses a unique approach where the Geiger's output is collected at the PC which then sends it to the Radmon.org website. (Instructions for connecting the basic kit to the Radmon app on a PC are on the Graphing to a PC page.)

However, the GK-WiFi and GK-RadMon software connects directly to the Radmon.org site, so a PC is not required.

A map on Radmon.org allows you to compare your readings with other's around the globe, and very nice set of graphs for your CPM data is provided. You can see my Radmon feed from the GKnet here.


ThingSpeak is a free IOT site with nice graphs and features. It can also interface to MATLAB, but I haven't tried it.

It's supported by the GK-WiFi and GK-RadMon software.


MQTT is not an actual IOT site, but rather it's a "lightweight messaging protocol for small sensors and mobile devices" (mqtt.org). With it, GK-RadMon or GK-WiFi will send its data ('publish') to a MQTT 'broker' that you define. That data can be read ('subscribed to') by another device. Some MQTT brokers also have a web interface that will allow you to see the data that you are publishing. Adafruit IO is one of these, and is shown on the left.

You may wish to use other brokers besides Adafruit IO. When using a broker that does not have a "dashboard" or interface, you must use some other application to "subscribe" to your feed.

  • I have made a "subscriber" ESP8266 sketch that subscribes to everything that RadMon+ sends to the broker. It outputs the values to serial, and optionally on an OLED.

The diagram below may you understand how MQTT can be used.


To get started with one of these sites, refer to the Build Instructions for GK-RadMon, or GK-WiFi.