Pomelo: Hand-held gamma-ray spectrometer

Battery-powered instrument for gamma spectroscopy with ample interfacing options

Similar projects worth following
Pomelo is a stand-alone instrument for gamma-ray spectroscopy. It uses a CsI(Tl) scintillator to measure gamma ray energies and can be operated using its buttons & graphical LCD interface. The hardware also supports USB, WiFi, Bluetooth, ZigBee, and an SD card. The whole thing is powered by a rechargable 18650 battery.

Pomelo is a complete instrument for hobby-level gamma spectroscopy. It is built around the Pomelo Core and Physics which handle all the radiation detection, but adds a user interface and ample communication in the form of an Arduino-compatible ESP32-C6 add-on board, the Pomelo Zest.

Pomelo Zest board displaying a Th-232 spectrum in logarithmic scale

The Pomelo Zest features:

A brief user interface demo of the instrument is shown in the following video.

The Pomelo Zest can be used as a generic ESP32-C6 development board, but its mechanical design is built to match the Pomelo Core and Physics so it might not be optimal because of the battery and power button placement.

Block diagram

Detector block diagram showing available connectivity for the system components. The Pomelo Core can still be accessed from a computer through USB for control and firmware update even while it also connected to the Zest

The software on the Pomelo Zest is written in the Arduino environment so it is very easy to follow and modify, but not optimized for low power consumption. However, the Pomelo Core stays powered when the Zest is switched off, so data can still be accumulated using little power.


Pomelo Zest schematic

  • Updated scintillator and power consumption

    mihai.cuciuc06/19/2024 at 17:30 0 comments

    Pomelo detector on the shoulders of giants

    I got the scintillators I intended to use with this detector and have some performance plots with them in this project log. With them the hand-held detector is also starting to look better. I added top & bottom laser cut acrylic plates as basic protection of both electronics as well as of fingers from the ~80V generated by the bias circuit.

    The detector consists of a top user interface & connectivity board based on the ESP32-C6 (Pomelo Zest), and a bottom gamma spectroscopy board (Pomelo Core). The power consumption of these two boards can be measured individually:

    Pomelo Core:

    • active: ~3 mA at background radiation levels

    Pomelo Zest:

    • active, connected to WiFi: 50 mA
    • active, LCD backlight on: 70 mA
    • active: 40 mA
    • light sleep: 0.7 mA
    • deep sleep: 0.35 mA
    • deep sleep with SD card inserted: 0.65 mA

    On future board revisions I intend to gate the power to the LCD and SD card.

    Here are some pictures of the detector with its laser cut acrylic protection plates.

View project log

Enjoy this project?



Gianmarko72 wrote 06/13/2024 at 08:02 point

this is a very interesting project.
is it going to be available in some form like kit?

  Are you sure? yes | no

mihai.cuciuc wrote 06/19/2024 at 16:17 point

Hi! Yes, that is the plan :) But it might take a while until I'm actually ready to sell these. Hardware is pretty advanced, but getting all the paperwork in order is something I'm not very experienced with.

  Are you sure? yes | no

Gianmarko72 wrote 06/25/2024 at 06:29 point

Hi Mihai
we will patiently wait :-)

  Are you sure? yes | no

kogosi wrote 06/07/2024 at 07:02 point

Hi, i´m Ralf. What Type ist the scintillator? I dont find anything in the Net. Thanks. Ralf from Germay ;-)

  Are you sure? yes | no

mihai.cuciuc wrote 06/19/2024 at 16:15 point

Hi, Ralf! I used a CsI(Tl) scintillator from OST-Photonics:

It's 3 cm^3, but I've since switched to 2 cm^2 ones :)

  Are you sure? yes | no

Gianmarko72 wrote 06/25/2024 at 06:30 point

Hi Mihai
why move to smaller scintillators? i thought the bigger the better (more chances to catch an event)

  Are you sure? yes | no

mihai.cuciuc wrote 06/25/2024 at 06:45 point

Hi, Gianmarko! The main reason I moved to smaller scintillators was that I read in someone's thesis that the reflective wrapping I use for the crystal works best when the aspect ratio of the crystal was at most 2:1. The previous crystals were 30 mm long with a base of 10 mm x 10 mm. Another reason is cost, as the price of the crystal goes quite linearly with size. Now the crystal and SiPM are in the same ballpark :)

  Are you sure? yes | no

juliaroberts981 wrote 06/07/2024 at 01:25 point

 Living in Castleford, UK, I've had my fair share of unpredictable weather. Trust me when I say that I've tried numerous weather forecasting tools, but nothing comes close to this one. It's like having a meteorologist at your fingertips! I've found the forecasts incredibly accurate, which is essential when planning outdoor activities. I've been able to avoid rain on my weekend hikes and even found the perfect sunny days for family picnics. Honestly, it's changed the way I plan my days. I strongly recommend for anyone needing reliable weather updates in Castleford.

  Are you sure? yes | no

Similar Projects

Does this project spark your interest?

Become a member to follow this project and never miss any updates