GS-Gamma-Recorder

Gamma spectacular, theremino adapters, non-sound card based, etc...
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Steven Sesselmann
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GS-Gamma-Recorder

Post by Steven Sesselmann » 11 Nov 2019, 11:54

I made this device for a client who wants to conduct areal gamma surveys by drone.
GSGR(3).jpg
Gamma Recorder front
GSGR(3).jpg (29.21 KiB) Viewed 348 times
It's essentially just a Raspberry-Pi-4 with a Python script that records a .wav sound file, but as these things go, the basic idea is simple, but final execution always ends up taking more time than expected (at least for me). I had the basic program working pretty well until I decided it would be more practical to write the file to a removable USB drive, that's when I discovered that simply plugging a USB stick into an RPI doesn't work, 10 hours later after reading all the posts by others who had the same problem, I finally found the work around.
GSGR(4).jpg
Gamma Recorder back
GSGR(4).jpg (36.52 KiB) Viewed 348 times
Anyway here is how it operates..

STEP #1
Insert the small black Lexar USB drive in any of the USB ports.
The gamma-recorder is programmed to only work with one specific USB drive, using it with other USB drives will require a change to the code.

STEP #2
Connect the GS-USB-PRO to any of the other USB ports.

STEP #2
Connect a USB power supply capable of at least 2.5 mA. and wait !!
The RPI will immediately start the booting up process (there is no on/off switch)
During the boot process, the RPI will look for and mount the USB drive
The python script will automatically execute and indicate ready when the yellow LED light comes on.

STEP #3
Start recording by pressing the red button once.
The yellow led will switch off
The red led switches on indicating that the system is recording.
Survey mission can begin

STEP #4
Stop recording by pressing the red button once and wait (be patient).
Both LED indicators will switch off while the computer is writing to disk.

DON'T REMOVE USB DRIVE UNTIL ALL ACTIVITY STOPS

You will see a blue led flashing in the USB drive twice
At this stage the recording has been saved on the drive as YYMMDD-HH-MM-SS.wav
Go to step 5 only when all activity has stopped and the yellow LED comes back on

< DECISION > Back to step 3 to start another recording or Proceed to step #5 to exit

STEP #5
Press and hold the red button for 5 seconds to unmount the USB and exit program.
The USB drive can now be safely removed and the files transferred to a PC for post analysis with Pulse Recorder and Analysis (PRA).


After the survey mission you simply transfer the audio file to a PC and open it in PRA. The objective with this kind of survey is to produce a time stamped 3D map which can then be mapped using GPS positions.

The exact recording end time is in the file name, so in PRA the bin size for count rate vs time can be set to say 60 seconds, so you can correlate counts with position.

I took the equipment for a test in my car and it performed as intended, although the 30 minute drive didn't reveal anything too interesting.

If anyone wants to try this route, just send me a PM, I am happy to share the python script and save you hours figuring out how to write to a USB drive.


Steven
kit.JPG
The whole gamma recorder kit with 3" detector
Steven Sesselmann | Sydney | Australia | gammaspectacular.com | groundpotential.org | beejewel.com.au |

Conor Whyte
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Re: GS-Gamma-Recorder

Post by Conor Whyte » 19 Nov 2019, 19:32

The A72 processor on the Pi4 runs wickedly hot!!! Anyone building their own pi recorder must have at least a 5V 3A capable power supply and an active cooling solution ( heatsink + 5V fan).
I use a 20A/hr battery pack that has a USB-C /3.1 power out ports for using it as a portable computer. The battery bank I have can supply the pi for a couple of hours.
I have found while you can power the pi4 with a 2.5A supply, on higher workloads there can enough current draw to cause the pi to brownout, and this can end up in a corrupted uSd card. Also, stay away from cheap
USB-C power supplies on amazon or Ebay. Many of these so called 5V 2.5-3A supplies in circulation are either simply not capable of delivering the current and as such fail to run the Rpi4 or can get piping hot leading to an eventual wall fire. AC noise, due to lack of filtering is also an additional issue that has popped up.

Here is a list of chargers/PSU that have been tested to their exact output.

https://lygte-info.dk/info/ChargerIndex%20UK.html

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Steven Sesselmann
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Joined: 27 Apr 2015, 11:40
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Re: GS-Gamma-Recorder

Post by Steven Sesselmann » 20 Nov 2019, 11:46

Conor,

Yes you are quite right, the processor on the Pi4 runs quite hot, so I added copper heatsinks on the processor and the two other chips, and yes the peak current draw can reach 2.5-3A but the way I configured the recorder, it was running without screen, mouse and keyboard, so even with the GS-USB-PRO and detector connected, the current draw was only around 0.8A while recording.

That said it needs a bit more current while booting up.

Recording a mono audio track at 48 kHz without any graphics is a very easy load for the Pi4, you could easily do it with a Pi-Zero.

Steven
Steven Sesselmann | Sydney | Australia | gammaspectacular.com | groundpotential.org | beejewel.com.au |

Conor Whyte
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Joined: 28 Apr 2019, 15:06
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Re: GS-Gamma-Recorder

Post by Conor Whyte » 20 Nov 2019, 14:42

Steven Sesselmann wrote:
20 Nov 2019, 11:46
Conor,

Yes you are quite right, the processor on the Pi4 runs quite hot, so I added copper heatsinks on the processor and the two other chips, and yes the peak current draw can reach 2.5-3A but the way I configured the recorder, it was running without screen, mouse and keyboard, so even with the GS-USB-PRO and detector connected, the current draw was only around 0.8A while recording.

That said it needs a bit more current while booting up.

Recording a mono audio track at 48 kHz without any graphics is a very easy load for the Pi4, you could easily do it with a Pi-Zero.

Steven
yes, that's quite a light load for the Pi4. --- speaking about graphics and such.... I wonder if a port of Theremino MCA could run on the pi under the new Unbuntu mate release?

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