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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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24th Mar 2023, 1:43 pm | #21 | ||
Heptode
Join Date: Nov 2018
Location: London SW16, UK.
Posts: 655
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
Quote:
Even high-quality camera lenses can contain lanthanum,zirconium and thorium dioxide....I still have my Canon 200mm F1.2 L super telephoto lens under my bed for years..but I doubt it is radioactive. Last edited by regenfreak; 24th Mar 2023 at 1:54 pm. |
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24th Mar 2023, 8:08 pm | #22 |
Octode
Join Date: Jul 2018
Location: Worthing, West Sussex, UK.
Posts: 1,003
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
Regenfreak
Which triodes are they?
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"Behind every crowd, there's a silver Moonshine" |
24th Mar 2023, 8:38 pm | #23 |
Heptode
Join Date: Nov 2018
Location: London SW16, UK.
Posts: 655
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
One of my high-power triodes is 811A which contains thoriated tungsten filament(mildly radioactive). I can't remember all the names of my high-power triode collection. I am a very untidy person, and they are stored in mountains of junk boxes at home.I have power triodes from the transceivers of the British Spitfire fighter and US Navy fighter planes, all containing thoriated tungsten filaments. Usually, they state it in the valve datasheets.
The Radium Girls used to lick the tips of the paint brushes for the luminous paint. Some highly collectable Leica camera lens are radioactive.... |
24th Mar 2023, 8:49 pm | #24 |
Octode
Join Date: Nov 2003
Location: Bath, Somerset, UK.
Posts: 1,806
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
I used a 555 oscillator circuit to drive a 240V to 9V transformer in reverse. To get the highest output voltage, I was able to tweak the oscillator frequency to match the resonant frequency of the transformer. I was able to achieve 425V which was sufficient to drive the tube.
Neil
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preserving the recent past, for the distant future. |
2nd May 2023, 9:01 pm | #25 |
Octode
Join Date: Jul 2018
Location: Worthing, West Sussex, UK.
Posts: 1,003
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
Just to update: I built and completed the Geiger counter, it was based on the R&EW design from April 1982 issue.
The original will not work as the interfacing in to the 7555 input (pin 2, trigger) is all wrong. You have to bias the pin 2 with 100k resistors to +5 volts and ground and couple in with a 100 nF capacitor from the collector of Q4. The mag is available here https://worldradiohistory.com/UK/Rad...1982-04%20.pdf I did however, have to build a completely different HT generator based on a flash gun transformer made by Jessops. I drove it it with a CMOS 4001 NOR gate oscillator and a VN10 FET mini power FET running at 9.64 kHz driving the tfmr, the best frequency that the tfmr worked at. Almost any cheap flash from a charity shop (usually £2-7) should do fine for an HT Generator for the Geiger-Muller tube. I designed it to run from a PP3 and to work down to 8.2 Volts, but it functions well below 7 volts Testing and Calibration I tried large transmitting tubes with Thorium/Thoriated filaments as a source, and none showed any readings. An old gas lamp mantle worked very well as a test source. To calibrate you will need a 100 Hz 1v P-P square wave source, the R&EW article describes how to do it.
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"Behind every crowd, there's a silver Moonshine" Last edited by Cruisin Marine; 2nd May 2023 at 9:30 pm. |
3rd May 2023, 11:15 am | #26 |
Banned
Join Date: Jan 2023
Location: Neath, Port Talbot, Wales, UK.
Posts: 286
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
Yes, the old gas mantles are really impressive. The new ones not at all.
Much more active than the uranium glass seems to be. I'd not thought of the flash gun approach. |