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Mittwoch, 8. Januar 2020

Be prepared for the atomic fallout



We live since a long time in peace and harmony. But the global situation has changed dramatically. The big players stopped speaking about demilitarization. They starting to build new weapons!

So, in the worst case, we have to deal with a atomic fallout. But radiation has no smell. You can´t see it. And it makes no noise. But if the radiation is high enough it will kill you in short time!

To measure radiation we need a tool called Geiger counter. This device can count the appearance of ionized radiation in the atmosphere. How does it work? The main part of the device is called Geiger Mueller tube. It is a tube filled with e. g. noble gases. In the tube is although a wire. The tube itself and the wire runs unter high voltage ( > 350 V). The ionized radiation in the tube let electrons flow between the tube and the wire and we can measure a short electrical impulse.

Geiger counters are not very cheap. If you want a good one, you have to invest more than 200 EUR. But there is an alternative from Amazon! I bought this one:

I modified the device to talk to an ESP32 and send the measurements to the cloud and via Bluetooth.

Lets get started:
To bring our brand new device online we have to connect it to an ESP32. I bought this one. But you can use every ESP32 clone you want. On one side of the Geiger board we see some pin headers. The pins are labeled with 'GND', '5V' and 'VIN'. 'VIN' is not correctly named. On this pin we get the impulses from the Geiger tube. We can connect our ESP32 to this 3 pins. Ground to ground and 5V to 5V. VIN can be connected to a input pin of choice.

This approach will work but it is not very accurate. The signal on the VIN pin came from a transistor and the level is bouncing. We count to much impulses. To get rid of this problem, we need a little circuit.

The IC in the middle of the schema is a good old 555 Timer IC. Connect Pin 2 of the IC with the output of the Geiger counter board. Pin 3 is the output of the 555 IC. Connect it with an input pin of the ESP32.

If you want to calculate a different output pulse width, you can use this online calculator:
http://www.ohmslawcalculator.com/555-monostable-calculator

The signal to the ESP32 is now crystal clear throw the monostable 555 Timer circuit. To get the things running, we need code for the ESP32.

Here is my version of the code:
https://github.com/rassware/Geiger-Counter-RadiationD-v1.1-CAJOE-

The code can post the data to thingspeak.com and can trigger a notification via IFTTT. It contains also a little web server to present the data on a nice website. Ready to crawl! I wrote a python script to scrap the data and send it to my homepage.

The results of my homemade radiation measurements can be watched at https://www.rassware.de/.





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