For makers who want to purchase the GGreg20_V3 Geiger counter module without a tube (because they already own a compatible tube or plan to source one elsewhere), this small technical note details the dimensions of the tube mounting on our module’s PCB.

As you can imagine, having the option to buy just the module can be very convenient for some. We have always provided this option (on our website, Etsy, and previously on Tindie) — allowing you to select and order only the components you need right now. Over time, we received feedback, gained experience, and discussed this matter with our customers.

Note: The GGreg20_V3 was originally designed for the SBM20 tube, but its Soviet-era stock quickly ran out, so we specifically chose the even better J305 tube as a replacement. This means the standard SBM20 will also fit the module, as it was the tube we originally designed it for.

It turns out that the Chinese market offers J305 tubes with varying dimensions. This is why we want to explain exactly which J305 tube (or similar) will fit the GGreg20_V3.

We provide data for the J305 tube that we currently supply with the GGreg20_V3. We use the data provided to us by our J305 tube supplier from China.

Further on, we include a technical drawing with dimensions and a few photos to clearly illustrate the setup.

We also provide a photo of several J305 tubes from the latest batch, which clearly shows that while J305 tubes have minor size variations, they can be considered identical for our purpose. In several years of working with the J305, we have only encountered two initially defective tubes, as well as one tube that significantly differed in size from the rest of the batch and from the dimensions specified in the datasheet.

We hope this publication will help you understand which tube to choose so that it fits the module, particularly in terms of length.

Good luck!
IoT-devices team

Our Idea

Over the past few years, we’ve encountered situations where a Geiger counter needed to be used simply and quickly, without specialized knowledge or experience, without connecting additional devices, and without complex communication. Of course, you could just count pulses and time them with a stopwatch. But we thought, why not create a convenient app for this? And we did.

Benefits of Using GGreg20_V3 with This App

• Affordable Solution: No need for a controller like Arduino, ESP8266, ESP32, or Raspberry Pi.
• Ease of Use: No programming skills required.
• Wireless: No need to solder or connect cables.
• Quick Start: No need to search for or pair a new device.
• Broadcasting: If needed, one Geiger counter can be used simultaneously by many users.

Who This App Is For

While this app isn’t precise and, paired with GGreg20_V3, isn’t a finished device, users who can’t or don’t want to program can immediately use the GGreg20_V3 module simply by powering it and installing this app.

But remember, this is only an educational, demonstration, and testing app for beginners. Please choose appropriate tools for appropriate tasks.

This app is also convenient for quickly testing the module’s functionality, for example, when picking it up at the post office.

For Accurate Measurements

If you’re looking for accurate and reliable measurements using the GGreg20_V3 module, we recommend checking out our other companion app for GGreg20_V3, which is about to appear on Google Play. That app uses a controller with Bluetooth as the data transfer channel between the module and the smartphone.

Please note: the BLE app requires significantly more work on the DIY project – at least knowledge of ESPHome, BLE Server, and controllers like ESP32 or Raspberry Pi Pico W, etc.

How It Works

GGreg20_V3 users only need the module powered (according to documentation) and this smartphone app. Wireless data transfer from the GGreg20_V3 module to your smartphone occurs via sound signals from its built-in buzzer. The app filters sounds captured by the smartphone’s microphone, recognizing only those that match the signals from the GGreg20_V3 buzzer.

Known Limitations

Using the wireless audio channel can lead to false readings or inaccuracies in noisy environments.

Specifically:

• Although the GGreg20_V3 Geiger counter can register all pulses that tubes like J305, SBM20, or LND712 are capable of in high-radiation conditions, this app has a significant limitation. To differentiate pulses, an artificial 70-millisecond delay between the pulses the app perceives had to be implemented. This means the app can correctly process radiation levels only up to 850 CPM (or 3 uSv/hour). This is entirely sufficient for normal household conditions but will be insufficient in the event of a nuclear disaster.
• While the app effectively filters events only of a specific frequency, there’s a problem of signal clutter, for instance, from a nearby conversation. In such cases, the signals overlap, and the app ignores relevant pulses.
• We’re also aware of an echo problem with relevant signals. This occurs in enclosed spaces. You can see this effect in the video in the app description on Google Play, where the buzzer pulses once, but the app sometimes counts them twice, likely due to echo. (For shooting this video, we use a lightbox where the echo occurs.)

Important Note

This app, like the GGreg20_V3 module, is not a precise measuring device. It’s intended for personal use, hobbies, learning, and creative experiments, not as a finished product. It’s created for DIY electronics enthusiasts.

Keywords

Geiger counter, GGreg20_V3, Ionizing Radiation, Companion Application, Conversion Factor, Geiger Muller Tube, DIY, IoT, Radiation Measurement, Embedded Electronics, Electronics

As new users of the GGreg20_V3 module may have noticed, the board now comes in black. The black PCB is likely the tenth generation of the GGreg20_V3 module. This version features an improved circuit for smoother high-voltage regulation and a voltage limit of approximately 600 volts.

The module also comes with two stickers. The first is a Q.C. (Quality Control) sticker on the back of the board. The second is a VOID (warranty) sticker placed on the module’s high-voltage adjustment potentiometer.

Since implementing these changes—over six months ago—we’ve had the opportunity to gather feedback from our customers. One of the most common questions directed at our support team has been about the VOID sticker. Naturally, people are curious (and sometimes even genuinely frustrated) about why we’ve restricted high-voltage adjustments and what this sticker actually means in practice.

Let’s go over everything step by step.

Over the past year (2023–2024), we grew increasingly concerned about the statistics on sudden module failures. Diagnostics consistently pointed to excessively high voltage as the likely cause. Over time, this inevitably damages module components and can even lead to the failure of the Geiger tube.

That’s why, starting around September–October 2024, we introduced several improvements to our internal quality control procedures. The Q.C. sticker is now applied at the final stage of product testing.

Additionally, we decided to further restrict access to the potentiometer’s settings.

Since the module requires precise tuning and this part of the circuit is analog, the potentiometer’s setting can be easily disrupted—whether during use, due to vibrations in transport, or for other reasons. We hope that the VOID sticker now serves as an additional safeguard, keeping the potentiometer fixed in the position set by our specialists.

This sticker also acts as a warning for both beginners and experienced users: if you’re not sure, don’t touch it.
Our goal is to ensure that anyone considering adjusting the potentiometer first makes sure they know what they’re doing, understands the correct procedure, and has the necessary tools.

Now, what about cases where adjusting the high voltage is actually necessary? As far as we know, there is only one such scenario: when replacing the Geiger tube with one that requires significantly different operating voltage.
For example, if you’re swapping a J305 tube for an SBM20 (or vice versa), there’s no need to adjust the module, since their recommended operating voltages are almost the same—380V for J305 and 400V for SBM20. However, if you’re replacing a J305 with an LND712, then an adjustment is necessary to change the operating voltage from 400V to 500V.

Some customers have asked: What should I do if I absolutely need to adjust the potentiometer to a different voltage?

Warning!

The module operates at voltages that can be hazardous to health and life. Do not violate safety regulations or electrical installation standards. If you’re unsure, it’s best to consult a qualified specialist with the proper experience and certifications.

Our Recommendations

1. Review the technical note on initial self-diagnosis of voltages on the GGreg20_V3 module.
2. Use the knowledge gained (see point 1) to correctly measure the voltages on the module without adjusting the potentiometer. Ensure that you are using the appropriate measuring tools and following the procedures outlined in the note.
3. Contact (via email) our support team to inform us that you plan to adjust the settings. If needed, consult with our specialists for guidance.
4. Adjust the potentiometer to the required voltage by removing the VOID sticker.

Conclusions:

• Since implementing Q.C. and VOID stickers as part of our improved procedures, we have not received a single report of GGreg20_V3 module failure.
• If you need to replace an SBM20 tube with a J305, there is no need to adjust the potentiometer. The operating voltage ranges of these Geiger tubes overlap, so you can simply swap the tube.
• Every module shipped with a Q.C. sticker has been properly calibrated and extensively tested. Our test bench records measurement statistics to verify the performance and stability of both the module and the tube over an extended testing period—typically about an hour. Only after passing these tests does our specialist approve the module for shipment.
• The extended final testing phase also allows for selective thermal control of module components, ensuring long-term reliability.
• The VOID warranty sticker on the potentiometer does not restrict you as a user. It simply serves as a warning that adjusting the potentiometer without proper knowledge and tools is dangerous. By breaking the VOID seal, the user knowingly accepts the associated risks.
• If you follow the documentation and handle the module correctly, you won’t need warranty service, repairs, or replacement for your GGreg20_V3.
• Simply leave the VOID sticker intact and avoid adjusting the settings unless absolutely necessary.

Since each user can choose one of many possible variations of the GGreg20_V3 configuration on the website and on Etsy when ordering, we conduct this analysis every year, because we are always interested in which configurations we need to have in stock the most to meet the needs of our online store users in a timely manner.

We also thought that potential buyers might also be interested in which GGreg20_V3 packages other radio amateurs order most often. So we decided to publish the statistics for the past year.

Option packages are available to order:

What we found this time

GGreg20_V3 Basic + J305 tube + Connectors (installed) and cables + Casing3d

In more than half of the cases, users ordered the complete configuration, which includes the module, the J305 Geiger tube, and two JST-JST and JST-Dupont cables and a protective 3D-printed case.

SKU of the set: ggreg20_v3_basic305_cabcas

GGreg20_V3 Basic + J305 tube + Connectors (installed) and cables

Almost a quarter of the orders included a J305 Geiger tube and cables in addition to the GGreg20_V3 module. Obviously, the casing was either not needed in these orders or the customer was able to print it out on their own, as the STL model of the casing is distributed by IoT-devices for free.

SKU of the set: ggreg20_v3_basic305_cab

GGreg20_V3 Basic + J305 tube

Twelve percent of our orders included the base module with the J305 Geiger tube. It’s surprising that only 12.2% of customers chose this option. We believe it’s the most optimal configuration in terms of price-to-functionality ratio. If you’re looking to save money while getting a fully functional, ready-to-use module, this variation is an excellent choice.

SKU of the set: ggreg20_v3_basic305

GGreg20_V3 basic

In more than seven percent of orders, customers have ordered the GGreg20_V3 module without additional options. We can add that such orders are usually intended to replace an existing Geiger counter module with the GGreg20_V3. Users tell us that they already have the tube and only need the module. Most often, the basic module without options is ordered by radio amateurs who know what they are doing. We also have long-term customers who have already bought modules from us twice, three times, and even four times, for which we are very grateful. We appreciate it and thank them for their trust and support.

SKU of the set: ggreg20_v3_basic

GGreg20_V3 basic + Connectors (installed) and cables

The rest of the orders, which is almost five percent, were for configurations containing the GGreg20_V3 module and cables. It’s good that we made this variation as well, because it was useful to a significant number of our customers.

SKU of the set: ggreg20_v3_basic_cab

Diagram

Table

Note. Please note that the data on replacements and repairs, which also sometimes occurred in 2024, are not included in the statistics we are discussing in this article.

Testing methodology

To conduct the measurements, we developed a special test bench based on the Home Assistant platform. The central element of the system was the Raspberry Pi Pico W controller with ESPHome firmware, which controlled the operation of the GGreg20_V3 module. To accurately measure the energy consumption, we used an INA219 sensor connected to a NodeMCU/ESP8266 controller also running ESPHome firmware. We used a laboratory power supply as a power source for the GGreg20_V3, which set the exact voltage level during testing.

Since the GGreg20_V3 module supports a wide range of supply voltages, from at least 3.0V to 5.5V, we used the three most common supply voltage levels to show how the test result differs: 3.3V, 3.7V, 5.0V. These voltages give us an idea of the module’s consumption when powered by:

• another controller or source with a voltage of 3.3V;
• a 3.7V lithium battery;
• another controller or source with a voltage of 5V.

It is important to note that the INA219 sensor measured only the power consumption of the GGreg20_V3 module, while the controllers were powered separately. This allowed us to obtain the most accurate data.

Also note that the supply voltage level did not change over time during the 60-minute test. Therefore, you should not expect that we have performed a complete emulation, for example, of a lithium battery that discharges under load and, accordingly, loses voltage from 4.2V to 2.5V during the test. Although this would have been a really useful and interesting experiment, we decided not to bother with it that much.

Test bench

Software on the side of the measuring sensor of consumed electric energy based on ESP8266 + INA219 with ESPHome firmware:

sensor:
 - platform: ina219
 address: 0x40
 shunt_resistance: 0.1 ohm

 current:
 name: "INA219 Current"
 accuracy_decimals: 5
 id: current_value

 power:
 name: "INA219 Power"
 accuracy_decimals: 5
 id: power_value

 bus_voltage:
 name: "INA219 Bus Voltage"
 accuracy_decimals: 5

 shunt_voltage:
 name: "INA219 Shunt Voltage"
 accuracy_decimals: 5

 max_voltage: 32.0V
 max_current: 3.2A
 update_interval: 1min

 - platform: integration
 name: "Total Energy Consumed"
 id: total_energy
 sensor: power_value
 time_unit: min
 accuracy_decimals: 5
 unit_of_measurement: "Wh"
 filters:
 - multiply: 0.0166666666666667

 - platform: integration
 name: "Total Current Consumed"
 id: total_current
 sensor: current_value
 time_unit: min
 accuracy_decimals: 5
 unit_of_measurement: "Ah"
 filters:
 - multiply: 0.0166666666666667

This YAML configuration snippet provides all the necessary data for our planned testing of the GGreg20_V3 radiation sensor module in terms of power consumption during operation under normal background radiation conditions.

Measurement process

The power consumption was measured every minute, with data accumulated for previous periods. The test lasted for an hour, which allowed us to obtain the real consumption of the GGreg20_V3 module for 60 minutes for each of the three supply voltages.

The Home Assistant platform was used to collect and record sensor data. It also provided tools for creating visual graphs of electricity consumption.

Results and conclusions

Thanks to the testing, we have obtained detailed data on the power consumption of the GGreg20_V3 module at different supply voltages. These results allow users to optimize the power consumption of their DIY projects using this module.

Power supply with a voltage of 3.3V

Power supply with a voltage of 3.7V

Power supply with a voltage of 5.0V

Summary of results

The power consumption of the GGreg20_V3 module was tested for 60 minutes at different voltages under normal conditions. INA219 measurement update cycle: 1 minute

Test dates: 27.08. – 31.08.2023

No deviations in radiation level measurements were observed during testing

Testing was performed in the default settings of the GGreg20_V3 module. The buzzer is enabled. The Schottky protection diode is installed. Blue power supply LED lights constantly. The supply voltage remained unchanged throughout the test cycle.

Appendix. Theoretical battery discharge diagram

We also decided to show the theoretical discharge graph at three different voltages when the GGreg20_V3 module is powered by batteries of different chemistry and capacity.

The basis for our calculations was the battery characteristics available on the Internet:

However, please note once again that this graph is a theoretical assumption and does not take into account the discharge of real batteries under load over time and changes in voltage and current consumption during discharge.

About GGreg20_V3

The Geiger counter module GGreg20_V3 manufactured by IoT-devices, LLC is the company’s flagship product, which has found its users in more than 30 countries.

All over the world, radio amateurs use GGreg20_V3 to create their own DIY projects, learn and conduct experiments related to radiation measurement.

When developing this product and improving it since 2020, we tried to make the module compact, ready-to-use, compatible with as many DIY platforms and systems as possible, undemanding in terms of power supply voltages, easy to program, and harmonized in terms of operating characteristics with various Geiger tubes.

We have also developed a number of examples and posted them on GitHub for various hardware and software platforms such as Arduino UNO, ESP32, ESP8266, Raspberry Pi Pico W, NodeMCU, ESPHome, Tasmota, MicroPython, Home Assistant.

And we, at IoT-devices Company, hope that our Customers will have a great user experience and real pleasure by implementing this module in their projects.

We also thank everyone for supporting and choosing this product designed and manufactured in Ukraine. We really appreciate it!

Keywords

Geiger counter

GGreg20_V3

Testing of energy consumption

DIY-projects

Home Assistant

Raspberry Pi Pico W

ESPHome

INA219

NodeMCU

ESP8266

I2C

WiFi

YAML

If you have encountered the same situation after updating your ESP32 devices with ESPHome firmware, we recommend that you check out our repository, which already contains a description and workaround for the issue. Here is the way to go:
https://github.com/iotdevicesdev/GGreg20_V3-ESP32-HomeAssistant-ESPHome

We also invite you to read the discussion on GitHub:
https://github.com/iotdevicesdev/GGreg20_V3-ESP32-HomeAssistant-ESPHome/issues/5

Best Regards,
IoT-devices Team

The DCDC_3V3_400V_V1 module is a high voltage source for powering a wide range of Geiger-Muller tubes with different anode-cathode voltage levels, and can also be used as a low-power high voltage source in other DIY projects.

The need to set different output voltage levels is one of the reasons for installing a tuning potentiometer in the module.

The other adjustment components are resistor R1 and capacitor C1.

For explanation, please see the block diagram below.

The left part of the block diagram shows the structure of the high-voltage converter DCDC_3V3_400_V1 module.

The right part of the block diagram shows the components of the power consumers from the DCDC_3V3_400_V1 module integrated into the DIY project, according to the user’s design.

The output cascade of the DCDC_3V3_400_V1 module is a high-voltage multiplier. In projects of radiation detectors based on the Geiger-Muller counter, the tube receives a high voltage of 300 to 2000 volts through the R1C1 circuit.

The resistance, capacitance and voltage values for R1 and C1 depend on the type of tube or DIY circuitry. For this reason, R1 and C1 are not installed on the DCDC_3V3_400_V1 module.

Another reason for the absence of R1 and C1 on the module is the possibility of damage (electrical breakdown) of C1 when adjusting the voltage with a potentiometer.

Taking these factors into account, we recommend that when testing the DCDC_3V3_400_V1 module, you solder or connect a circuit to the output contacts according to the following scheme:

The voltage adjustment and measurement should be performed similarly to the steps described in the Initial Diagnostics Manual for the Geiger counter module GGreg20_V3.

Before you begin

1. The components of the device contain dangerous voltages. Do not violate safety precautions and rules for handling electrical installations.

2. To maintain the warranty of the device, users are not allowed to adjust the potentiometer themselves. To make changes to the module settings, please first obtain authorization and instructions from the support team.

3. Please note that if you use a conventional voltmeter (not the one required by this manual) to measure high voltage on the GGreg20_V3 module, the measurements will be inaccurate and insecure. Often, inaccurate measurement and adjustment leads to the device being inoperable or damaged.

Please do not attempt to measure high voltage with inappropriate tools.

A conventional voltmeter may show 150V, while the real voltage value may reach 500V, which is guaranteed to damage the module or tube. The multimeter can also be damaged.

Also, a conventional multimeter may not have the necessary speed to convert the analog values being measured.

And finally, note that high voltage measurements are performed on a capacitor, so do not forget to give it time to charge before the next measurement.

Getting started

1. Disconnect the module from the MCU board and provide power to the module via the corresponding connector on the module (BAT).

2. Inspect the detector board with a magnifying lens for damaged components.

3. Check the input DC power supply voltage Upower_supply that is supplied to the module. The input DC voltage must be between 3.0 and 5.5 V. The power supply must be at least 5 watts (1 amp at 5 V).

4. Check whether the J305 tube is properly mounted on the holders. Caution! The electrodes of the tube and some other components may contain dangerous voltages for a long time after switching off.

5. Turn on the GGreg20_V3 detector module without the case to access the diagnostic points.

6. The blue LED lights up normally.

7. The red LED does not blink (the buzzer does not beep, there are no pulses at the output, even with a jumper).

1. Tools needed

Note: Alternatively, a multimeter with the above characteristics can be used. However, an oscilloscope will be much more convenient for this task.

2. Diagnostic actions

Objective: to obtain data on voltages:

• on the module’s power supply points (low-voltage part);
• on the module’s elements of the high-voltage part.

2.1 Diagnostic points

2.2 Low Voltage Measurement

2.2.1 Make sure that the DC voltage level of U5V at the point shown in the Fig. is 5V +-5%.

2.3 High Voltage Measurement

2.3.1 Set up the oscilloscope and probe as follows:

– Select the input channel, set the mode to DC, 10 volts per division.

– Set the switch on the probe to the 1:10 position.

– Sampling rate (number of signal points per unit time): 1 division per 1 second.

– Set the function of fixing instantaneous maximum voltage values.

2.3.2 Carefully connect the oscilloscope’s GND pin to the module’s GND. To do this, point the GND pin (or solder a wire) to the point “GND” shown in the Fig. Measure the voltage level at the point shown in the Fig. with a probe.

2.3.3 Make several measurements of U400V. Between measurements, pause for 5-10 seconds, which is necessary to restore the capacitor charge level. Observe on the oscilloscope screen the waveform of the capacitor discharge by the input resistance of the oscilloscope and the measured maximum voltage values. The correct voltage value should be as follows: 380 +- 40 volts for J305 tube.

Warning:

a) A voltage of 400 volts is dangerous to the human body.

b) Inaccurate positioning of the oscilloscope probe at the measurement point may cause damage to other components.

3. Observed Data Collection and Reporting

Please contact our support team with the measurement results (Upower_supply, U5V, U400V). We will provide additional instructions.

We have previously written about how to calculate the coefficients for the SBM20 tube and the J305, tube that come with our Geiger counter module GGreg20_V3 for DIY / IoT projects.
However, in those articles, we focused heavily on the calculation formulas and almost overlooked a very important detail: when calculating the conversion factor for the Geiger tube pulse count, we need to be aware of what exactly we want to get as the output.

If we need to obtain the radiation power of a radioactive source registered by the counter, this is one task.
It is a completely different task when we need to obtain the equivalent value of the radiation dose absorbed by the human body over a certain period of time.

We describe in detail how to calculate the coefficients in our previous publications, so we will not waste the reader’s time now.
Instead, we will try to show the differences between the calculated coefficients and how best to use them for a DIY project.

The data is provided for the J305 tube. Any other Geiger tube, such as the SBM20 or LN712, can also be used in its place, since they all have a similar principle of operation except for certain nuances that we can neglect for the purposes of this discussion.

In our previous publications, we went from start to finish: we have pulses -> we want to keep the value in μSv/h.
Today we will try to go the other way: from the goal of the DIY project through the sequential steps to achieve it.

As DIY Geiger counter users, we would most likely want to have access to the following information on our device’s display:

1. CPM: The number of registered pulses per minute received from the counter;
2. μSv/h: The radiation power of the source registered by the counter;
3. μSv: The absorbed dose by the human body over a certain period of time.

Take a close look at these values. The secret to calculating them correctly lies not only in the correct formulas and coefficients, but also in understanding the overall process:

• The source emits radiation;
• The counter registers it;
• The human body absorbs it.

The human body does not absorb everything that the counter registers. The counter readings and the absorbed dose are highly dependent on many factors. Therefore, to simplify the measurements, it is common to use ready-made data from the manufacturer and equivalent models for calculating the corresponding coefficients.

Pulse Count

We obtain the pulse count from the Geiger counter module. For convenience of calculations, as well as based on the pulse density during normal background radiation measurements, this parameter is best calculated in counts per minute (CPM).

For example, the J305 manufacturer specifies in the datasheet that the tube should emit 25 pulses per minute under normal background radiation. In other words, 25 CPM.

Why do we need the CPM value on the display if there are other, more understandable indicators? Indeed, it is possible to do without pulses per minute. However, it is a very convenient indicator when we want to understand if there are any malfunctions in the device. Usually, in our devices, we make a cumulative counter of the number of registered pulses for the entire time the device has been operating since the power was applied.

In this case, even if we do not have a source of accurate synchronized time, such as NTP or RTC, we can still calculate the average number of pulses per minute by dividing the sum of all pulses by the total time elapsed since power was applied. This indicator can indicate the quality of our data, even if hours have passed since the device was turned on.

We hope that since the principle of such checks is already known to you, you will develop your own algorithms for checking the data quality and the operation of the counter if necessary. There can be many implementations.

Radiation Source Power

When we want to estimate the radiation source power, we need to apply the conversion factor from CPM to μSv/h obtained by calculation based on the data specified in the tube’s datasheet from the manufacturer:

For the J305 tube, the manufacturer specifies a sensitivity of 44 cpm per 1 μR/h from a Co-60 source;

Let’s convert the data we need:

1. Converting to counts per minute at 1 mR/h:

CPS / mR/h → CPM / mR/h: 44 * 60 = 2640;

2. Converting to counts per minute at 1 μSv/h:

CPM / mR/h → CPM / μSv/h: 2640 / 10 = 264;

3. Value of one pulse per minute in μSv/h:

1 / ( CPM / μSv/hr ) = 1 / 264 = 0.00378;

Therefore, if we need to convert the pulses registered by the J305 tube during a minute to μSv/hour and obtain the radiation source power value:

1 CPM = 0.00378 [μSv/h];

or

When we read the documentation for a Geiger tube, this is the parameter that is usually discussed.

Equivalent Dose Absorbed by the Human Body

To obtain the value of the equivalent dose of radiation absorbed by the human body, we will apply the model of a human body phantom:

1. Lets convert counts per second to counts per minute at 1 mR/h:

44 * 60 = 2640 pulses/minute / mR/hour

2. Convert CPM at 1 mR/h to CPM at 1 R/h:

2640 * 1000 = 2640000

3. Let’s find the value of the exposure dose R/h at 1 CPM:

1 / 2640000 = 0.0000003787878788

4. Find the air-kerma (Ka, kinetic energy released per unit mass/in matter):

The equation is as follows:

Ka [Gy] = 0.00877 [Gy/R] x exposure [R]

where 0.00877 – radiation dose absorption coefficient by the human body on a phantom model under the influence of photon energies of 100 keV – 3 MeV

0.00877 * 0.0000003787878788 = 0.000000003321969697 Ka[Gy]

5. Let’s convert Ka[Gy] to Ka[μSv] (i.e., from Gray to μSv):

0.000000003321969697 * 1000000 = 0.003321969697 Ka[μSv]

Thus, the formula for the equivalent absorbed dose of radiation by the human body for the Geiger-Muller J305 tube with gamma sensitivity for Co-60 of 44 cps/mR/h is as follows:

Please note: To obtain the cumulative value of the equivalent dose of energy absorbed by the human body, we need to add the hourly values to the previous accumulated sum throughout the entire measurement period (from the moment of power supply or resetting the counter value). See the example below.

Why should we be more interested in the dose of radiation absorbed by the human body than in the radiation source power? There are at least two reasons for this, which follow from each other.

First, from the point of view of radiation safety, it is not the power of the source itself that is important, but the dose that we will absorb over a certain period of time if we are exposed to the radiation source.

Second, since the dose of absorbed radiation is so important, it is the dose for humans that is calculated and provided by government organizations for radiation protection and public health.

Usually, the permissible dose is given for a period of one year. It is such tabular data that allows us to objectively assess what is the normal level of background radiation – the moment when the radiation source power and the equivalent dose absorbed by the human body can be converted to common units and compared.

If the normal background level, in terms of its instantaneous power converted to a year, turns out to be higher than the permissible dose per year, then this may not be background, but a certain radioactive source. And then something needs to be done immediately with the radiation source that creates such a “background” so as not to exceed the permissible absorbed dose of radiation by our body.

Practice and Examples

Now we come to the most important thing: when creating sensor entities for GGreg20_V3 with a J305 tube, for example in ESPHome, we need to use the appropriate coefficients for different physical values.

1. Number of pulses per minute is always just the number of pulses – a dimensionless value. But if necessary, a conversion or averaging coefficient can also be applied (not considered in this article);
2. For radioactive source power: CPM * 0.00378 [μSv/h];
3. For the equivalent dose absorbed by the human body: CPM x 0.00332 [μSv/h], finding the sum of the minute-by-minute values [μSv] for the entire measurement time.

Example for ESP32 + GGreg20_V3 + J305 у ESPHome

# 1. Pulse Count Sensor from a Counter with a 60-Second Measurement Cycle

 sensor:
- platform: pulse_counter
 pin:
 number: 23
 inverted: True
 mode: 
 input: True 
 pullup: False
 pulldown: False
 unit_of_measurement: 'CPM'
 name: 'Ionizing Radiation CPM'
 count_mode: 
 rising_edge: DISABLE
 falling_edge: INCREMENT # GGreg20_V3 uses Active-Low logic
 use_pcnt: False
 internal_filter: 180us # for J305
 update_interval: 60s
 accuracy_decimals: 0
 id: my_cpm_meter

# 2. Radiation Source Power Sensor with a 60-Second Measurement Cycle

- platform: copy
 source_id: my_cpm_meter
 unit_of_measurement: 'uSv/Hour'
 name: 'Ionizing Radiation Power'
 accuracy_decimals: 3
 id: my_power_meter
 filters:
 - multiply: 0.00378 # for J305

# 3. Sensor for Equivalent Dose Absorbed by the Human Body per Hour with a 60-Second Measurement Cycle

- platform: copy
 source_id: my_cpm_meter
 unit_of_measurement: 'uSv/Hour'
 name: 'Ionizing Radiation Equivalent Absorbed Energy'
 accuracy_decimals: 3
 id: my_dose_meter
 filters:
 - multiply: 0.00332 # for J305

# 4. Cumulative Equivalent Dose Absorbed by the Human Body from Radiation Since the Start of Measurement (i.e., from the Moment of Power Supply)

- platform: integration
 name: "Total Ionizing Radiation Equivalent Absorbed Energy Dose"
 unit_of_measurement: "uSv"
 sensor: my_dose_meter # link entity id to the pulse_counter values above
 icon: "mdi:radioactive"
 accuracy_decimals: 5
 time_unit: min # integrate values every next minute
 filters:
 # cumulative absorbed dose. Converting it from uSv/hour into uSv/minute: [uSv/h / 60] OR [uSv/h * 0.0166666667]. 
 - multiply: 0.0166666667
 # but if my_dose_meter in CPM, then [0.00332 / 60 minutes] = 0.000055; so CPM * 0.000055 = dose every next minute, uSv.
 #- multiply: 0.000055 # for J305

Conclusions

In this article, we made an important discovery that the coefficients for different tasks for the same Geiger tube should be different. This approach differs from the examples that are given on the Internet.

Although we have already written in passing about different coefficients (see articles on calculating conversion coefficients), in our numerous examples on GitHub , we previously used only one coefficient, because that’s what everyone does.

Now we believe that it is better to calculate a separate coefficient for each sensor entity depending on its type and purpose. Perhaps we will even update the YAML files in our examples on GitHub.

References to other publications and examples

UA: Geiger tube J305: How to calculate the conversion factor of CPM to μSv/h Technical note
EN: Geiger tube J305: How to calculate the conversion factor of CPM to μSv/h. Technical note

UA: Технічна нотатка: Як розрахувати коефіцієнт перетворення для трубки Гейгера СБМ20
EN: Technical note: How to calculate the conversion factor for Geiger tube SBM20

UA: Трубки Гейгера-Мюллера: порівняння SBM20, J305 та LND712
EN: Geiger-Muller tubes: Comparison of SBM20, J305 and LND712

EN: DIY Geiger counter GGreg20_V3 on GitHub

Easy Links

Unique Vendor ID: https://go.iot-devices.com.ua/ggreg20_v3
User Friendly ID: https://go.iot-devices.com.ua/geiger-counter

Where and how to order

Website Online Shop
Etsy Store
Tindie Marketplace

According to our statistics, the J305 tube is second only to the Soviet-made SBM20 tube in terms of prevalence among DIY Geiger counter projects.

However, time passes, technologies improve, and supply chains change. New products and components are steadily occupying their niche on the shelves of electronics suppliers, gradually displacing temporary solutions from the market, which, in fact, was the Soviet SBM20 tube in the DIY electronics market.

If we were asked to compare SBM20 and J305 tubes, we would choose J305 for our project, as we have already mentioned in a separate publication. This article compares J305, SBM20, and LND712 tubes that we have worked with and with which the Geiger counter module GGreg20_V3 is electrically compatible.

This publication also describes the J305 tube as the closest and best alternative to the SBM20 tube, in our opinion. We will look at how to calculate the conversion factor for converting the number of pulses per minute of the J305 tube into the value of μSv/h, the equivalent dose of radiation absorbed by the human body.

The Internet widely publishes data that the conversion factor for the J305 Geiger tube is 0.00812.

0,00812

As in the case of the SBM20 tube, we had to carefully search the Internet for the original source of this information. Unlike the investigation of the coefficient for SBM20, our search for data on J305 was successful and led us to the primary source of the common coefficient of 0.00812.

But let’s not get too far ahead of ourselves and set out everything in order.

Here are the general technical characteristics of the tubes so that we can look at them while studying the calculations that follow.

Some formulas and calculations

As for the SBM20 tube, the calculation procedure for the J305 tube will be the same.

We will make calculations for J305 based on the manufacturer’s data.

The rate of event registration by the J305 tube at 1 μR/h from the Co-60 source is 44 pulses per second;

1. Let’s write down the initial data from the manufacturer’s datasheet. Pulses per second at 1 mR/hour:

44 pulses/s / mR/h

2. Convert to pulses per minute at 1 mR/h:

44 * 60 = 2640 pulses/minute / mR/hour

3. Convert to pulses per minute at 1 μSv/h:

2640 / 10 = 264 pulses/minute / μSv/h

or

264 pulses/minute = 1 μSv/h

or

1 pulses/minute = 1:264 μSv/h

4. Calculate the value of one pulse per minute:

1 / 264 = 0,00378

Thus, if we need to convert the pulses detected by the J305 tube during a minute to μSv/hour:

Everything would have been fine, and we could have stopped calculations there. But the coefficient we have just obtained

0,00378

gives us the exposure value recorded by the Geiger counter. We are primarily interested in the equivalent dose of radiation absorbed by the human body.

Therefore, let’s move on to the next part of the calculations.

In order to estimate the equivalent dose of energy absorbed by the human body, science uses the so-called human body phantom model, which calculates certain conversion factors for converting one value to another.

If you are interested in reading the theory on this subject, we can advise you to read this publication:

https://web.archive.org/web/20230402162906/https://www.automess.de/en/service/radiation-quantities-and-units

We now proceed to derive the conversion factor for converting the CPM of the tube into an equivalent dose of absorbed radiation in microsieverts per hour, taking into account the phantom model of the human body.

Let’s start the calculation with the coefficient provided by the manufacturer in the documentation: 44 imp/s per 1 mR/h of Co-60.

J305 sensitivity to gamma rays: 44 CPS/mR/h

1. Let’s convert pulses/s to pulses/minute at 1 mR/h (we already have this value, but we are going to calculate it again for the reader’s convenience):

44 * 60 = 2640 pulses/minute / mR/hour

2. Convert CPM at 1 mR/h to CPM at 1 R/h:

2640 * 1000 = 2640000

3. Find the value of the exposure dose R/h per 1 CPM:

1 / 2640000 = 0.0000003787878788

4. Find the air-kerma (Ka, kinetic energy released per unit mass/in a substance):

The equation is as follows:

Ka [Gy] = 0.00877 [Gy/R] x exposure [R]

where 0.00877 is the coefficient of radiation dose absorption by the human body on the phantom model under the influence of photon energies of 100 keV – 3 MeV

Note . For the air-kerma equation and coefficients, see the link: the link: https://web.archive.org/web/20230402162906/https://www.automess.de/en/service/radiation-quantities-and-units

0.00877 * 0.0000003787878788 = 0.000000003321969697 Ka[Gy]

5. Convert Ka[Gy] to Ka[uSv] (i.e., switch from Gray to µSv):

0.000000003321969697 * 1000000 = 0.003321969697 Ka[uSv]

6. Perform the check and find the inverse value:

0.003321969697 ^(-1) = 301.0262258

Thus, the formula for the equivalent absorbed dose of radiation by the human body for the Geiger-Muller J305 tube with gamma sensitivity for Co-60 of 44 cps/mR/h is as follows:

where

0.00332 μSv/h is the value of one count, pulses/min;

CPM is the number of counts (events) per minute detected by the Geiger tube.

Something is wrong here

Well, an attentive reader will say, but where is the number 0.00812, which was mentioned at the beginning of the calculations?

You are right! We were also surprised: as a result of the calculations, we got the coefficient equal to 0.00332, but we expected that the calculation should result in a value of 0.00812. That is, a completely different number for the CPM to μSv/h conversion factor.

We started searching on the Internet and found it.

As it turned out, most of the examples of settings for the J305 tube simply refer to each other, but we did find out where this coefficient came from.

Follow the link (or here, in PDF on the Libelium website) to find a document with the following data:

“…The current version of the pack comes with the J305ß Geiger tube which detectes Beta and Gamma radiation.
Specifications:
Manufacturer: North Optic
Radiation Detection: β, γ
Length: 111mm
Diameter: 11mm
Recommended Voltage: 350V
Plateau Voltage: 360-440V
Sensitivy γ (60Co): 65cps/(µR/s)
Sensitivy γ (equivalent Sievert): 108cpm / (µSv/h)
Max cpm: 30000
cps/mR/h: 18
cpm/mR/h: 1080
cpm/µSv/h: 123.147092360319
Factor: 0.00812037037037…”

Everyone refers to this text and there is no way to verify the data, because the website of such a manufacturer as North Optic does not exist.

The most surprising thing is that respectable resources also publish (or allow users to do so) this coefficient without the note “Attention! No one knows where it came from.”

Note. Please contact us if you have any information on how to contact North Optic or explanations on the reliability of the 0.00812 coefficient. Thank you in advance. Thank you in advance.

As you can see, the original data provided by North Optic is very different from the data currently provided by Chinese manufacturers with their tubes.

For comparison, here is the datasheet for the J305 glass tube we have. These are the tubes that we use to equip the Geiger counter module GGreg20_V3:

Fig. Characteristics of the J305 tube from the manufacturer’s datasheet

Given the materials we found, it is at least clear where the numerical value of the conversion factor of 0.00812 comes from.

Look, from the mathematical point of view, everything is very simple:

[18 CPS / mR/h] x 60 / 8.77 = 123.1470923603193

1 / 123.1470923603193 = 0.0081203703703704

Here, we immediately applied a quick formula and obtained a conversion factor of 0.00812 for a tube with a sensitivity of 18 CPS / mR/h.

Indeed, if we assume that the tube has a sensitivity of 18 CPS / mR/h, then the coefficient should be exactly 0.00812.

But the 2022 J305 tube that suppliers sell through Alibaba in 2023, and that we hold in our own hands, has completely different properties. Declared by the Chinese manufacturer in the datasheet: 44 CPS / mR/h.

Conclusions

We provided a complete algorithm and showed how to calculate the conversion factor of CPM to the equivalent dose of radiation absorbed by the human body (uSv/h) for a Geiger tube such as J305.

We also considered two variants of the conversion factor.

The first is the one we calculated based on the data in the datasheet: 0.00332.

The second is the one that everyone uses: 0.00812

It is up to you to decide which conversion factor you prefer to use.

Examples for ESPHome

We would like to remind you that the GGreg20_V3 module is compatible with both tubes: SBM20 and J305.

On our GitHub , you will find several examples of ESPHome firmware configuration files for both SBM20 and J305 handsets. The difference is only in a few coefficients of these tubes:

• CPM -> uSv/h conversion factor;
• coefficient of compensation of internal noise of the tube (for cases when it is used).

Currently, ESPHome is a fairly common and popular platform with wide support for a variety of MCUs, such as ESP8266, ESP32, RaspberryPi Pico W, and others. That’s why most of the examples in our GitHub repositories are aimed at and based on the ESPHome firmware and Home Assistant server.

Where to order GGreg20_V3

You can order the Geiger counter module GGreg20_V3 on our website, as well as on one of our electronic platforms:

• Online shop: go.iot-devices.com.ua/shop
• Etsy store: go.iot-devices.com.ua/etsy
• Tindie store: go.iot-devices.com.ua/tindie

If ordered, the GGreg20_V3 module is equipped with several additional options to choose from. Among them:

• Geiger tube J305
• cables for connection to the MCU
• protective 3D printed plastic cover for GGreg20_V3

Please also note that you can also order the ESP12.OLED_V1 universal controller module (based on the ESP8266) on our website.

Both of these modules are sufficient to build a DIY Geiger counter with a display:

[GGreg20_V3] + [ESP12 .OLED_V1] = [DIY Geiger counter]

We hope that this and our other publications were useful and interesting.

Good luck!

Team IoT-devices, LLC