Hobbyist background radiation detector that counts Alpha,Beta and Gamma.

[SpottedDick]

Hi all,

First of all, a Geiger counter typically isn't a very accurate device to start with. The hobbyist ones, even worse. So take into account that this is just for fun and a rough measurement.

I came across an old post discussing measuring background radiation and differentiating between them.

The plan I had all those years ago was to use three of the usual tubes you get from AliExpress but:

1. Alpha tube should be as exposed as possible.
2. Beta tube should be enclosed enough to try and remove as many of the Alpha particles as possible.
3. Gamma tube should be in an aluminum pipe.

The way this works, is that we would update the CPM (counts per minute) every 5 minutes. Each channel gets measured for 100 seconds, and then we do a little math to get our CPM for each channel.

Electronically, I'd still use the same base that I currently use which is this circuit:



The idea would be to switch between the three tubes with physical relays. All three will be permanently connected to the high voltage, but switched at the negative side. Disconnect a tube, connect the next.

Any thoughts on this?

[Uunoctium]

If I may be so frank to make a comment: it has now become common practice to extract the signal at the anode. The few data sheets from LND Inc that I have seen always show the pulse decoupling at the anode in circuit examples of their GMT's. And Analog Devices provides the explanation for this in its App Note CN-0536.
https://www.analog.com/media/cn/reference-design-documentation/reference-designs/cn0536.pdf

[SpottedDick]

You don't need to preface that message with "if I may be frank", this is something that has been rolling around in my head for a while, and it's probably stupid, so I love getting any sort of feedback on it.

The cathode made sense to me due to the circuit diagram, and I'm heading to bed now, but I will look at your doc in the morning. Thanks.

[daisizhou]

Why didn't you choose to use a high pressure ion chamber solution?

[Doctorandus_P]

I would put in a microcontroller, just as with any electronic project these days. There are so many additional functions you can put into a uC, that keeping with an only analog design would feel very limiting.

Some ideas:

• Dosimeter.
• Adjustable alarm thresholds.
• Calculate ratio between Alfa / Beta / Gamma ratios
• Data logging over time.
• Only enable the speaker above a certain radiation threshold.

I'm wondering what would happen to the world if Uunoctiom may not be frank.
SpottedDick? Maybe go see a doctor.

[SpottedDick]

Can you expand or give a link to a product that does what I want?

[SpottedDick]

I mean, the whole thing is going to be monitored with a micro-controller. I'm just posting and focusing on getting the pulse output right for the three radioactivity types.

The above circuit I posted is designed for a microcontroller, I have it connected to both an ESP8266 for sending to my home automation, and a nano for a live display.