<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></head><body dir="auto"><div dir="auto">Reply from my contact in the radiation world.</div><div dir="auto"><br></div><div dir="auto">Peter</div><div dir="auto"><br></div><div dir="auto"><br></div><div dir="auto"><br></div><div id="composer_signature" dir="auto"><div style="font-size:12px;color:#575757" dir="auto">Sent from my Galaxy</div></div><div dir="auto"><br></div><div><br></div><div align="left" dir="auto" style="font-size:100%;color:#000000"><div>-------- Original message --------</div><div>From: Gareth Thomas <jgbcthomas@talktalk.net> </div><div>Date: 12/03/2025 21:25 (GMT+00:00) </div><div>To: "'peredur.net'" <peredur.net@gmail.com> </div><div>Subject: RE: [Swlug] DIY Geiger counter </div><div><br></div></div><div class="WordSection1"><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Hi Peter</span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Rhys seems like a keen electronics guy. What he describes is making a solid state photo luminescent ionising radiation detector rather than a much more basic ‘regular’ Geiger counter. It is a long time since I studied the electronics of radiation detectors so not sure I have the answers he is seeking, but I am pretty sure most Geiger counters don’t ‘store’ the electrical pulses, they just amplify them to a sufficient level to be able to register them on a needle or electronic display.</span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Gareth</span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span></p><div><div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm"><p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif" lang="EN-US">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif" lang="EN-US"> peredur.net [mailto:peredur.net@gmail.com] <br><b>Sent:</b> 06 March 2025 16:47<br><b>To:</b> Gareth Thomas <jgbcthomas@talktalk.net><br><b>Subject:</b> FW: [Swlug] DIY Geiger counter</span></p></div></div><p class="MsoNormal"> </p><div><p class="MsoNormal">The mail below cropped up in my inbox, and I thought, "Who do I know who works with radioactive materials?"</p></div><div><p class="MsoNormal"> </p></div><div><p class="MsoNormal">Peter</p></div><div><p class="MsoNormal"> </p></div><div><p class="MsoNormal"> </p></div><div><p class="MsoNormal"> </p></div><div id="composer_signature"><div><p class="MsoNormal"><span style="font-size:9.0pt;color:#575757">Sent from my Galaxy</span></p></div></div><div><p class="MsoNormal"> </p></div><div><p class="MsoNormal"> </p></div><div><p class="MsoNormal"><span style="color:black">-------- Original message --------</span></p></div><div><p class="MsoNormal"><span style="color:black">From: Rhys Sage via Swlug <<a href="mailto:swlug@mailman.lug.org.uk">swlug@mailman.lug.org.uk</a>> </span></p></div><div><p class="MsoNormal"><span style="color:black">Date: 06/03/2025 16:34 (GMT+00:00) </span></p></div><div><p class="MsoNormal"><span style="color:black">To: South Wales Linux User Group <<a href="mailto:swlug@mailman.lug.org.uk">swlug@mailman.lug.org.uk</a>> </span></p></div><div><p class="MsoNormal"><span style="color:black">Cc: Rhys Sage <<a href="mailto:rhys_sage@yahoo.com">rhys_sage@yahoo.com</a>> </span></p></div><div><p class="MsoNormal"><span style="color:black">Subject: [Swlug] DIY Geiger counter </span></p></div><div><p class="MsoNormal"><span style="color:black"> </span></p></div><p class="MsoNormal">I'm in the middle of a project - to build a Geiger counter. It's a fun project so far.<br><br>I have all the bits I need (I think) but as with all projects there's a lot of experimentation and changes made on the fly. <br><br>I'm using a Thalium-doped Cesium Iodide crystal in combination with a BPX61 photo diode. For those that don't know- the BPX61 is slightly more sensitive to green light. The crystal emits blue/green light when struck by gamma radiation. Whether it emits light when struck by Alpha, Beta or X-Ray, I don't know. I do know there are other crystals more suited to those.<br><br>The BPX61 output will feed into an OPA134PA amplifier and then that will in turn feed into a microcontroller. Given that the events generated by radioactive decay are very brief, would microcontroller speed make much difference? I could use an ATTiny13/ATTiny85 or something small like a micro RP2040 or an ESP32 C3 Super Mini.<br><br>With a regular Geiger counter,does the system store the events somehow or does it just rely upon measuring maximum pulses when a pulse happens during a sampling period?<br><br>Rhys Sage<br><br>-- <br>Swlug mailing list<br><a href="mailto:Swlug@mailman.lug.org.uk">Swlug@mailman.lug.org.uk</a><br><a href="https://mailman.lug.org.uk/mailman/listinfo/swlug">https://mailman.lug.org.uk/mailman/listinfo/swlug</a></p></div></body></html>