MyGeiger ver.2 Dosimeter DIY Geiger Counter Kit with LCD Shield and USB

Why choosing MyGieger ver.2.00 over others DIY Geiger Kits? MyGeiger is the high quality and professional Do It Yourself kit of dosimeter that can be used for home and educational nuclear radiation measuring. The project mostly intended for hobbyist, enthusiasts, students and scientists. The device is easy to use and has opportunity to configure the hardware for many popular Geiger tubes, such as SBM-20, LND-712, SI-29BG, SI-180G and more.

There are many others DIY Geiger Kits on the market today. All of them are good for their own reasons as amateur devices. When designed MyGeiger version 2.00 we tried to eliminate the design flaw related to all of others DIY Geiger Kits, such as high current consumption and HV fall under radiation load over 0.5mSv/h. MyGeiger ver.2.00 consumes only 5mA at background (other kits can drawn more than 30-50mA even at background); MyGeiger produce stable tube High Voltage to ensure that tube works within plateau limits (other kits has HV fall under real radiation fast count  down to 350V); MyGeiger was tested with SBM-20 and CT x-ray radiation up to 1700uSv/h 300000CPM so it promised to operate stable in real radiation levels up to 1000uSv/h and it excellent for standard device.

MyGeiger ver. 2.00 has carefully crafted electrical circuit diagram with improved software algorithm. As a result, now we have more professional and stable device with all important for portable dosimeter functions, but the project still kept easy for soldering. Even it has SMD components installed on PCB, you need to solder only DIP through hole parts.

Tiny power consumption: MyGeiger ver.2.00 has twice reduced power consumption, now it less than 5mA at background without backlight. At background radiation dosimeter can continuously operate during 200 hours with one 3.7V Li-PO 1000mAh. With one 3800mAh - 4200mAh Li-Ion it can operate during 30 days without additional charging. Tiny power consumption allows you using MyGeiger for pocket continuous monitoring day by day and charge battery when USB is available.

Built-in lithium charger: The board has built-in lithium charger with protection circuit which abolishes the need to carry a special li-ion charger. Indicator led will inform you about charge status. You can charge the kit’s battery directly from your computer or from any 5V power supply with USB jack. Another important new function is battery over-discharge limiter protection. When cut-off 3V battery voltage reached, device goes into sleep mode with about 0.5mA (500uA) power consumption. Then you need to power off the kit and connect USB for charging.

Battery Indicator and USB connection detect: New edition has improved battery indicator and USB connection detection.

Powerful MCU: MyGeiger ver.2.00 run on PIC18F2550 powerful microprocessor. It has better performance and bigger memory in compare to the older edition.

Tube high voltage: Now you can select tube voltage for 400V or 500V output. Even under high radiation load, or when battery is discharged, high voltage stays between tube plateau limits. This functions fully controlled by original software algorithm. The algorithm takes care about tube voltage under high speed count load and keep HV in recommended plateau.

New High Quality Graphic Display: The kit comes with high quality graphic LCD with blue backlight. The display has very tiny power consumption and it’s readable in daylight even without backlight. The display comes pre-installed on LCD Shield board.

Auto Scaling CPM Graph: Keeps all CPM readings for the last 5 minutes in graphical representation. The graph is auto-scaling and auto-scrolling with nice flow on the LCD.

Built-in USB support: MyGeiger kit has built-in USB support and you can log data to computer directly, without external TTL modules! The kit can log CPM (counts per minute) or Bq/cm2 data every 5 seconds.

Logging Software: For CPM data you can use our freeware “Radiation Logger” Windows application or freeware RadMon application. For Bq/cm2 logging we supply link to download third-party UART terminal program, it also freeware and easy to use.

Radiation Dose Units: MyGeiger ver.2.00 can displays radiation dose automatically in uSv/h, mSv/h or uRn/h, mRn/h units. You can switch between the Sv an Rn units with “-“ tact button, make a short push once. The counter will remember your choice in eeprom memory. Accumulated dose in uSv units is also presented on LCD. Each time you power the dosimeter, a new accumulated dose count starts.

Measuring Period: The dosimeter has moving average radiation counting with every 5 seconds data updates.

Maximum Radiation counting ability: Maximum radiation counting ability for DIY Geiger kit is correlation of 3 factors: software interrupt capability, high voltage stability and GM tube type. When talking about maximum radiation count, the common mistake is reporting only microprocessor counting ability. But it also important to take into consideration GM tube HV stability under maximum count load. SBM-20 capable to register up to 1.5mSv/h (300K CPM). This is realistic maximum level even the processor can count more CPM. MyGeiger was tested with SBM-20 and CT x-ray radiation up to 1700uSv/h 300000CPM so it promised to operate stable in real radiation levels up to 1000uSv/h and it excellent for standard dosimeter.

MyGeiger ver.2.00 mostly intended for home and laboratory usage, testing radioactive samples or monitoring gamma radiation level. Instead of SBM-20 you can connect any other compatible GM Tubes, such as popular 400V/500V alfa-tubes, just remember to change software settings to get right radiation readings.

Kit sound and Silent Operation: Kit has improved sound, very close to the classic Geiger counters clicks. You can mute the buzzer and led flasher by pressing “+” tact button for reducing power consumption and silent operation. Your settings are saved to eeprom memory.

Alarm: You can set CPM alert value during device start-up. Your choice is written to eeprom memory for next usage. Alert is settable with 10 cpm steps from 10-200 and with 100 cpm steps from 200-5000. When radiation levels becomes dangerous, the LCD backlight will be activated to inform you about high level. It’s possible to use alarm function with external relay module or with second alarm buzzer / led, additional wiring required in this case.

There are several software settings you need to set in calibration menu when using different tube model:

“Conversion Factor” used for conversion from CPM to uSv/h units. Default is 0.0057

"BG” maximum normal background CPM level for your tube, default is 30

“SQ” surface area of your tube in square centimeters units, default is 22

“DL” is detect limit, calculated by software from your BG and SQ parameters, you do not need to set this parameter. BG, SQ and DL used for calculating Bq/cm2. Becquerel logging actual for testing small size radioactive samples, that physical size is smaller than tube surface size. Becquerel mode is experimental function that currently we are not guarantee it has high precision results. Becquerel logging mode is not intended to measure background radiation.  

"DT" is tube dead time settings. This option available since firmware 2.15 only. Dead time value set in microseconds between 1us-250us, depend on your tube model. Maximum dead time value can be found in Geiger tube datasheet, but in practice every GM tube may slightly differs. The actual value can be determined with an oscilloscope. By default you can use datasheet value if no oscilloscope available. For example SBM-20 has maximum 190us.

Dead time settings affect dose rate calculation only. No difference for background or moderate CPM activity, but noticeably in high radiation condition. Set it for 1us if you do not want to use dose correction.

To select tube voltage you need to set DIP Switch 1. Off position for 400V and On position for 500V. Then trim 2K potentiometer to the middle position. Power the kit and check voltage value on LCD. For 400V tubes it has to be between 400V-450V, and for 500V tubes between 500V-550V. If you read more or less then turn off the kit and trim 2K a little right or left. After check voltage again. Do not trim potentiometer when kit is powered! You need to find optimal settings for the potentiometer.

Model	Voltage Set	Factor	BG	SQ
SBM-20	400V	0.0057	30	22
SI-29BG	400V	0.0081	15	12
SBM-19	400V	0.0021	100	80
SI-180G	400V	0.0031	70	42
SBT-9	400V	0.0117	10	16
SBT-11	400V	0.0050	30	5
J305 / M4011	400V	0.0081	20	25
LND-712	500V	0.0081	15	16
LND-7317	500V	0.0024	50	16

MyGeiger ver.2.00 requires one Lithium Polymer or Lithium Ion 3.7V battery. You can use branded or no-name types, just take care about connector polarity in advance. Main PCB has PH 2.00mm connector that fits polarity for this Li-PO battery from SparkFunhttps://www.sparkfun.com/products/339 You can use others 3.7V lithium battery types and capacity, but be carefull about right polarity.

It's recommended to use at least 800mAh or 1000mAh capacity, but it also possible to run on one 10440 AAA size Li-Ion. In this case you'll need to charge the battery every 2-3 days because AAA size batteries usually has 300mAh capacity only. Otherwise when running the kit with 3800mAh-4200mAh capacity battery you can use the dosimeter non-stop on background radiation count during 30 days.

Important point to understand that any additional modules, high radiation level or LCD backlight impact power consumption directly. That's why when using the dosimeter in high radiation area during long term period you need to carry additional batteries or have an option to charge from USB. Good advice for portable charging is solar powered cell phone charger. This devices has 5V output with USB jack.

Here is the summary table with power consumption of the kit under different conditions. On normal background radiation the kit drawn about 5mA only without backlight. With high radiation count, and depend on HV settings, it can consume from 8mA to 30mA with LCD backlight powered. With 2.15 firmware you can set the backlight to manual activation that reduce total consumption.

 

Test Condition	400V  SBT-10	500V  LND-712
Normal Background Radiation	4.5mA	5.5mA
Normal Background + LCD Backlight	8.0mA	9.0mA
12000 CPM + LCD Backlight	8.5mA	10.0 mA
150000 CPM + LCD Backlight	12.0mA	30.0mA

Computer Logging:

MyGeiger has built-in FTDI FT232RL virtual COM Port IC for USB logging. You need USB cable with mini-usb male connector. To allow logging please download and install FTDI FT232RL drivers: http://www.ftdichip.com/Drivers/VCP.htm

 

USB Serial Port Settings:

• Baud Rate: 2400
• 8 Data Bits
• Parity none
• 1 Stop Bit

 

Radiation Logger Software:

Please download the latest version of PC logger software from our website: https://www.rhelectronics.store/rad-logger

Pre-set counter for CPM output, in kit’s calibration menu “Bq to UART”, press “-” for NO.

Radiation logger software works with Windows OS. It allows creating CSV logs file on your PC and build graphs from previously saved logs files. Since 1.4 logger version it support direct uploading to http://xively.com and to http://radmon.org  

 

Becquerel Output Logging:

Becquerel logging actual for testing small size radioactive samples, that physical size is smaller than tube surface size. Becquerel mode is experimental function that currently we are not guaranteeing its precision results. Terminal.exe is an excellent COM port freeware application with configurable connection settings and ability to create log files. You can use it for writing Becquerel logs data.

Download and run Terminal.exe program. Pre-set counter for “Bq to UART” in kit’s calibration menu, press “+” for YES.