Check out the new RadMon kit if you're interested in a monitoring device.


The first "DIY Geiger Kits" were produced in 2011, shortly after the Fukushima disaster. The goal was to have a low cost solution for the sudden interest in radiation detection. It was one of the first Geiger counter kits available. Since then there have been severial models and many improvements.

These kits provide the electronics needed to run, and detect events from a GM tube. The events are counted and displayed as CPM and dose rate by a microprocessor running preloaded software. Counts can also be output to a PC via a serial connection.

Assembly requires moderately good soldering skills, and the ability to read and follow the Build Instructions supplied. Geiger Kits are not an "instant Geiger counter" ready for field use. They do not include a GM tube, battery, case and controls that you may wish to put on a case. However, with these simple additions the kits are a fully functioning Geiger counter.

The kits will work with GM tubes that require high voltage in the range of 350-940V (which is most tubes.). For a list of tubes that have been successfully used with the kit, see GM Tube Info.

The GK-B5 and GK-Mini kits use an ATmega328P. The GK-Plus kit uses a larger ATmega1284P. All have all pins broken out and an FTDI connector that will allow it to be programmed with the Arduino IDE if desired. See the Software page for more info.

Getting more info:

This site should provide a good overall view of each kit type. However you can get a more detailed understanding by downloading the Build Guide and User Guide for the kit you are interested in. You might also check out the Gallery of finished kits to see what others have done with this kit. Of course you can also contact me with specific questions.


If "imitation is the sincerest form of flattery" then I am truly flattered! But I should first define what I call a knock-off (clone is another word).

From the beginning, the software I've written for the kit is open source, and the circuit is thoroughly defined. I did this thinking that people who wanted to build their own could reference what I have. Of course there were some who just wanted to sell a kit, and I expected they would build on my ideas by adding their own ideas and create something new and different. This has happened in some cases. However, there are some who apparently just want to "cash in" by taking the design, software, hardware and even the documentation and the name, and adding little if anything to the project. These, I call "knock-offs" or more politely "clones". If you want to see a fun video on this subject check out EEVblog #333 - Unwritten Rules of OSHW.

Have you been reading "Sour Grapes" ? Honestly, not really - that's just the way it is. Should you buy a clone? Of course that's up to you. My only advice is that you consider the differences. Looking at what is here should help you make the best choice. I should be the last person on earth to point them out, but if you'd like my opinion on a particular point, let me know. No matter what, enjoy your Geiger counter. They are surprisingly interesting.

Types of Kits Available:

For many years only one model of Geiger Kit was available - the GK-B5. Now other models are available; the GK-Plus a more advanced kit, and the GKmini a simpler and smaller kit. In addition there are RadMon and GK-WiFi kits that provide connection to the internet. Each has their own page and description available from menus at the top or clicking on the heading. Below is a snapshot of each.

This is by far the most common model of Geiger Kit. Over the years it has evolved and improved through 6 major revisions to its latest design.


Below is a bullet list of some of the features of the GK-B5

  • ATmega386 microprocessor is Arduino “Uno” compatible with all I/O pins
  • the standard 2x16 LCD display simply plugs into provided headers
  • runs with a 9V battery or AA batteries
  • high voltage power supply – adjustable from 200 to >940 volts
  • miniature speaker instead of piezo for a classic Geiger counter sound
  • FTDI connector outputs activity to serial port
  • interfaces to various graphing programs and the free “Geiger Bot” phone app
  • highly evolved Version 12.0 software pre-installed
  • display in CPM and choice of uSv/h, uR/h or mR/h
  • uses a running average for count display along with a fast acting bar graph
  • two scalier displays for 1 minute and user defined accumulated counts
  • alarm for high counts with settable threshold triggers off of either CPM or dose
  • Setup Menu - configure parameters and features with the included TV remote
  • Tone Mode - optionally set speaker to produce a tone that varies in pitch with activity. (like a metal detector)

The video above should help you understand the basic functionality of the GK-B4 Geiger Kit.

The GK-Plus provides all the features of the GK-B5 along with a graphic display, SD card, clock, GPS support, and a more powerful processor.


This kit uses one surface mount part that is not too difficult to solder. The SD card, GPS module, and GM tube are not included. There are more details and videos on the Geiger Kit - GK-Plus page.

This is a smaller version of the GK-B5 kit, with fewer components that is faster to build. However it provides virtually all the functionality of the GK-B5. The GK-mini uses an Arduino Pro-mini compatible processor on a plug-in board.

There are more details on the Geiger Kit - GK-mini page.

This kit is a dedicated radiation monitoring station. Add a GM tube, and it sends its readings to monitoring and IOT websites like Radmon.org, ThingSpeak and MQTT brokers. This is an ESP8266 based kit that uses WiFi to connect to your local network.

You can use solar power to power this kit giving you a totally wireless monitoring system.


RadMon (basic)


with OLED


solar powered

This is an extension to the GK-RadMon kit described above. It's software is designed to eliminate the need to program the ESP8266. The network and site credentials are entered through screens using the browser on your phone or notebook. The ESP8266 comes pre-programmed and ready to go.

The PCB is sized to fit a larger weatherproof case and the OLED is now a formal part of the unit.

There are more details on both of these kits on the Geiger Kit - GK-RadMon page.


RadMon Plus

This is a kit attaches to the serial port on any Geiger Kit. It reads the output, and sends it to monitoring and IOT websites like Radmon.org, ThingSpeak and MQTT brokers. This is an ESP8266 based kit that uses WiFi to connect to your network.

There are more details on the Internet Logging Kits page.


GK-WiFi attached to GK-B5



small size