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Global Radiation monitoring system

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tobias

Thu Jul 11 2013, 11:44PM

Registered Member #1956 Joined: Wed Feb 04 2009, 01:22PM
Location: Jersey City
Posts: 172

You can always add the GPS footprint on the board and have the option of soldering it or not..
With GPS no time adjusting is needed. Why would you need buttons for a 'mobile' version? If it has battery, it is logging.

If you plan on having backup logging why not to add backup power? Lipo charger ICs are easy to deal with. And it would work ok without a battery as well.

Also, I would think it is nice to monitor temperature as well.

Can you make it water/dust proof if not using humidity/pressure sensor? That would be a nice trade-of.

For the outside-mount case. Get one with nice mounting tabs =)

macona

Sat Jul 13 2013, 05:44AM

Registered Member #3272 Joined: Mon Oct 04 2010, 11:40PM
Location: Beaverton, OR
Posts: 101

I would not use a 0 or 1 as an indicator. Use something more well know like a radio button (Circle for off, circle with dot in the middle for on). When using a display with a lot of numerical data having status displayed as numbers is kind of bad UI design.

Why not use an OLED instead of a backlight? Or try one of the Sharp memory LCDs. The use an incredibly small amount of power to run.

But for me I cant really see the point of the whole thing. It just gives people data about something they dont understand and get scared.

radhoo

Sat Jul 13 2013, 09:40AM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

@tobias, buttons are needed to setup the dosimeter alarm, eg. when the measured dose gets higher than a given threshold. This threshold comes with a defautl value, but must be changeable by the user. Also if you look at the display picture above, you'll see the content is almost entirely used by the Geiger indications only. Let's not forget about the other functionality like the additional sensors, or the GPS data. I might want to build charts for the various readings. The user will need some kind of input to browse through all of that... and a minimalistic software menu.

The external power backup is a good idea. Since this also works as a data logger, I'll see the final power consumption and decide on how to prolong its power source autonomy.

It should be dust/waterproof and for mounting externally there will be some addon tabs.

@macona, what do you mean by 0 and 1 indicator? The LCD I chose is already a low power lcd, with the backlight assured by 4 side leds.

Last days I was thinking about the direction the entire project is heading. Initially I wanted to make this an exclusive monitor, using high sensitivity tubes such as SBM-19 or SI-22 . Deciding to make it portable implied reducing size, so instead of the large tubes I went for the SBM-20. Not as sensitive but considerably smaller.

I'd like some feedback on this: was it the right choice? Is the reduced size a compulsory feature for a portable dosimeter, trading the SBM-19 for the SBM-20?

Here's a video showing some very good performance when measuring a Ra226 source contained in a 1b24 tube:

tobias

Sat Jul 13 2013, 07:49PM

Registered Member #1956 Joined: Wed Feb 04 2009, 01:22PM
Location: Jersey City
Posts: 172

Radhoo

I see more use on a 'mount outside my home/apt and forget' type of device. First of all, by connecting all in a network you want lots of data, 24/7, from devices all over the world. Best case scenario, multiple stations at the same city so you can corroborate data.

After you have that going, mobile devices will gain more importance. At least is what I think, as by the nature a mobile one will not be logging continuously.

Here is my list of ideas for the device:
1- No screen, no buttons, no HMI whatsoever. All to be done by remote access. On a browser or PC/android software. To have the alerts on my cell would be awesome!
2- Only two ports. A RJ45 and a USB. The RJ45 for data, USB for power and/or firmware upload. Multiple uCs today support usb bootloaders. And if something goes wrong you can always open the box up and go ISP.
3- A embedded 3,7V Lipo Charger to keep a small battery ready for power disruptions.
4- Enough memory to fill out when loosing connectivity.
5- Upload to a central server or something were you can se data not only from your node, but all the ones around you
6- A GPS would further reduce the HMI need. No time or location adjustment needed.
7- A vibration sensor would be nice =) Earthquakes, somebody hehe

If you do go with mobile, put a bluetooth module so you can configure it from the smartphone. It will save space, and maybe money depending on the cost of that display you have.

macona

Sun Jul 14 2013, 07:18AM

Registered Member #3272 Joined: Mon Oct 04 2010, 11:40PM
Location: Beaverton, OR
Posts: 101

radhoo wrote ...

@macona, what do you mean by 0 and 1 indicator? The LCD I chose is already a low power lcd, with the backlight assured by 4 side leds.

Ehh, forget it. I misunderstood what you said in an earlier post.

You might consider bluetooth instead of a RJ45 or at least an option. Then you can just upload to a smart phone and to a server of your choice. You could also work with the guy who wrote Geiger Bot on the iphone and get it to work as an input device for that. Geiger Bot supports bluetooth audio so you could send a raw bluetooth audio stream to the phone and let it do the heavy lifting.

radhoo

Mon Jul 15 2013, 09:59AM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

Thanks both for your suggestions.

There's another issue I'm confronting with, again it's a matter of choice.

Because I wanted to make the device portable (but not an issue if used only as a monitor), I had to trade the sensitive SBM-19 tube for the smaller-but-less-sensitive SBM-20. Background counts for SBM-19 is at 80cpm, while the SBM-20 barely touches 20. For short term readings this might result in unwanted variations from the true environment radiation dose, but would not be an issue when integrating the data over a larger time interval (a few hours or so).

SBM-19 is 19cm in length, while the SBM-20 is only 11cm:

Linas

Tue Jul 16 2013, 02:22PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

i have one question, how can you by knowing only "ticks/s" calculate Sv ?
And if you can, what is the error of calculation? (i always can't get my head around this all calculations)

Steve Conner

Tue Jul 16 2013, 02:35PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

The conversion between counts per unit time and sieverts depends on two conversion factors:

The "quality factor" of the radiation (how much damage 1 particle worth of it does to human tissue)

The sensitivity of the detector (how many particles it takes to produce one count on average) This depends both on the type of detector and the type of radiation, for example most Geiger tubes can barely detect alpha particles because they can't penetrate the outer wall of the tube.

Linas

Tue Jul 16 2013, 02:41PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

Steve Conner wrote ...

The conversion between counts per unit time and sieverts depends on two conversion factors:

The "quality factor" of the radiation (how much damage 1 particle worth of it does to human tissue)

The sensitivity of the detector (how many particles it takes to produce one count on average) This depends both on the type of detector and the type of radiation, for example most Geiger tubes can barely detect alpha particles because they can't penetrate the outer wall of the tube.

that is my point, it just way to much parameters that goes into play, and it is only possible to know the answer with a error of constant (if that is linear process, but i have doubts about that)

Steve Conner

Tue Jul 16 2013, 03:07PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I agree, I think this device is so inaccurate that it'll only be good for scaring people.

However I've seen Russian Geiger counters that read out in uSv/hr probably using a similar setup and calibration, so maybe there is a precedent for it.

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