Sorry no PIC here.

[JonW]

Seems to be alot of people on here monitoring radiation....   

[Wimax]

What is the current consumption of your Geiger Counter?

Hello Ken,

I confess I have to resurrect it, I parked it for several months waiting for parts from AliExpress so I could integrate it in an encloser ... devoting the time to other projects. Tomorrow I will try to check it out!

[Wimax]

Tip: If you place a voltage divider at the high voltage generator with 1 GOhm resistor and cheap pico-amp amplifier, you can set the Geiger tube voltage, monitor it without loading the generator and keep the high voltage constant. Here's one rock ... 

It's a smart solution, reading the voltage and changing the duty cycle ? I adopted a cascade of zener diodes to limit the HV, Data-sheet aside...I was a bit sceptical about how the zener actually works, but I had to change my mind.
Congratulations for the presentation of the data, that display is very nice!

[ken_k]

Tip: If you place a voltage divider at the high voltage generator with 1 GOhm resistor and cheap pico-amp amplifier, you can set the Geiger tube voltage, monitor it without loading the generator and keep the high voltage constant.

You design looks outstanding the GPS is a nice touch. I was unaware 1 GOhm resistors were available at such a reasonable price. Can you adjust the tube voltage via software?
This Geiger Counter design may turn into a competition! Maybe my next one should have double overhead chrome plated grease nipples.

[Fanie]

A Geiger tube will have an optimal voltage it will perform best from.
When exposed to bombardment will increase current flow, through a resistor can be detected and amplified.
A G-ohm resistor sounds like instability to me.

I cannot remember how the geiger tubes looked that we used, and I cannot remember that they ever went faulty despite the extreme conditions they worked in.  I would think the larger the tube, the more sensitive it can be for a specific radiation.  Certain tubes will be better for certain emissions, depends what it was designed for.

If you need 170V for a tube, it may not be so easy to generate that off a battery to get a calibrated output, but it can be compromised by using a small tube with less resolution that still give an acceptable indication for detection.
If you are to go on a site where there is contamination you would probably wear a tag that indicate when you had your dose of radiation (for the next 500 years  ) irrespective of what your instrument showed.  The more or less clicking is only an indication which direction the hornets nest is and if there is one.

Audible output is preferred to visual because it is difficult to watch the indicator when you move over difficult terrain.

[Fanie]

Btw, not all radiation is bad for us.  IR radiation is apparently good, while UV is considered bad, and fortunately UV-C is mostly shielded by the atmosphere.  Perhaps there is a form of nuclear radiation that is good for us, imagine you become a glow-in-the-dark without ill effects... or your eyes emit red beams enhancing your night vision.  Or just think you become invisible... I will be sooo naughty if that happens 

[trastikata]

A Geiger tube will have an optimal voltage it will perform best from.
When exposed to bombardment will increase current flow, through a resistor can be detected and amplified.
A G-ohm resistor sounds like instability to me.

This is why I regulate the voltage every few 10s of milliseconds. The high voltage monitoring is built around this circuit, the 1 GOhm resistor loads the high voltage circuit insignificantly and because it is behind the capacitor tank it is quite accurate.

Indeed the high tube count draws more current and the current circuit lags or overshoot with 3-5 volts when there's a high count change.

[Fanie]

I would use a power supply for the tube and a simple amplifier measuring a voltage over a resistor on the neg of the tube.  If the tube supply voltage does change with emission (ie conducting more), it will not matter because it would be in relationship with the amp output you get and can be compensated for very easy.
If you breathe on that G-ohm resistor it will change value...
I would use lower value resistors and rather amplify the smaller voltage output. 

[Fanie]

Something like this


The current flow through RVt will generate the input voltage to the opp amp.  The value should be so that the voltage is within the opp amp range.
If you're going to use a pic then the damping components to the right of the perforated line can be omitted as it is very easy to average the output of the amp, and / or read peak value(s) with the software.
For audio you can generate the clicking going faster as the emission increase, or play a low to high tone,
and beyond a certain value you play Les's Death March 

[Wimax]

What is the current consumption of your Geiger Counter?

Hello Ken,

Counter resurrected...current consumption is 60 mA @ 6VDC with LCD always on.
Below two pictures of my creation, with the tube alone (on the left) and with a little bit of ThO2  (alfa, beta and gamma emission, but the tube stops the first... the decay time roughly equal to the age of the universe ).
Beside the Dspic33FJ and the LCD there is a nice old-style piezo buzzer for the ticks.

[trastikata]

Something like this
The current flow through RVt will generate the input voltage to the opp amp.  The value should be so that the voltage is within the opp amp range.
If you're going to use a pic then the damping components to the right of the perforated line can be omitted as it is very easy to average the output of the amp, and / or read peak value(s) with the software.

I am confused here or I misunderstand the concept - the current flowing through the resistor depends on the number of electrons from the avalanche effect in the tube. This number however will depend from tube to tube, also very much on the state of the quencher gas, so how this can be related to the voltage at the tube anode?

[Wimax]

Yes I'm confused too, in normal conditions the tube behaves as an open circuit and you can try to stabilize the HV, when you have interactions with particles, gas ionization due to avalanche effect, the voltage drops, then a current flows through the resistor (and you can conveniently detect the pulse).
----------
----------
Assuming the tube is new, which is unlikely, I have found an apparently reliable formula on the net to go from the easily measurable CPMs to the dose in air.
I believe the factor used is too high, i.e. Dose= CPM*0.00812, based on the tube's stated sensitivity =18 cps/mR/h for Cs-137.
Months later and with the help of ChatGPT it seems that for the beta/gamma decay of the auer 200 HK net the most suitable conversion factor is 1/850.
Trastikata did you used Thorite ?

[trastikata]

Trastikata did you used Thorite ?

In the picture above is Thorite as written on the bag - rare natural thorium-uranium mineral.

https://en.wikipedia.org/wiki/Thorite

P.s. For SBM-20 the generally accepted conversion factor is 170-190 CPM per µSv/h. Looking at the local radiation monitoring station online and measuring the background outside, I think my tube is close to 190 CPM per µSv/h.

[ken_k]

or your eyes emit red beams enhancing your night vision.  Or just think you become invisible... I will be sooo naughty if that happens

Maybe xray vision.  https://www.youtube.com/watch?v=IkBdPW545gA

[ken_k]

P.s. For SBM-20 the generally accepted conversion factor is 170-190 CPM per µSv/h. Looking at the local radiation monitoring station online and measuring the background outside, I think my tube is close to 190 CPM per µSv/h.

I guess you have lots of data on the SBM-20.
Can I post a .mhtml? I have added a .txt and will try. Remove the .txt
Parameters and characteristics SBM-20.mhtml.txt

Quick edit, very interesting it worked.

[Wimax]

Very interesting! I had found something on the net some time ago, but my Cyrillic is really bad!
The problem is that the SBM-20 tube has a non-linear sensitivity characteristic, a commonly adopted coefficient for CPM/dose conversion is 0.0057, but it neither corresponds to the equivalent dose absorbed by the human body (according to the phantom model), nor does it seem to be related to the manufacturer's declared data.
I found this number in scientific paper, but here there is an interesting discussion, the most suitable coefficient seems to be 0.00812 when the tube has been calibrated with a Cs-137 source.

What about the current consumption of your Geiger Counter (mine is near 60 mA @ 6 VDC, with LCD on) ?



And just to mention artificial intelligence...ChatGPT advised me to use, an SBM-20 tube, a factor of 1/850, Deepseek 1/50...

[ken_k]

Very interesting! I had found something on the net some time ago, but my Cyrillic is really bad!
The problem is that the SBM-20 tube has a non-linear sensitivity characteristic, a commonly adopted coefficient for CPM/dose conversion is 0.0057, but it neither corresponds to the equivalent dose absorbed by the human body (according to the phantom model), nor does it seem to be related to the manufacturer's declared data.
I found this number in scientific paper, but here there is an interesting discussion, the most suitable coefficient seems to be 0.00812 when the tube has been calibrated with a Cs-137 source.

What about the current consumption of your Geiger Counter (mine is near 60 mA @ 6 VDC, with LCD on) ?

Thank you for the above, very good information.

Due to the fact the supply voltage for the boost converter is taken from the input DC voltage  and not the regulated 5V rail the CMOS geiger counter draws less current on a full 9V battery.

I disconnected it from its test battery today and wired it up to a bench supply via a 100 ohm series resistor so I could measure the voltage drop across the resistor and calculate the current.

9V input, speaker off, background radiation, supply current 220uA.

9V input, speaker off, background radiation, full scale on a 100uA meter  supply current 380uA.

7V input, speaker off, background radiation, supply current 670uA.

9V input, speaker on, high click rate with a thorium mantle over the GM tube, around 2.5mA. The click is loud a series resistor to the speaker may be in order.

The speaker drive circuit is from a darlington emitter follower so the drive voltage to the speaker remains the same, it's collector is connected to battery voltage in to avoid ripple on the 5V rail.

I expect to improve the HV power supply. My goal it to improve performance and reduce the current consumption.