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17th Mar 2023, 10:32 pm | #1 |
Heptode
Join Date: Jul 2018
Location: Worthing, West Sussex, UK.
Posts: 983
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Step up transformer from 9 to 575 volts for a Geiger tube.
Am in the process of building a Geiger counter. I am initially planning on using a 555 at something like 100 kHz, driving a transistor and a step up transformer to increase a say 7 volt DC regulated supply from a pp3 battery supply source.
Anything from say 150 volts AC at bugga' all current will be fine 'cos I can use voltage multipliers easily on the secondary. Any ideas greatly appreciated. Thanks PS the title of the thread needs editing, I typed too fast and posted- ty.
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17th Mar 2023, 10:46 pm | #2 |
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Re: foStep up transformer from 9v to 575 volts r a Geiger tube
Look up "Boost converter" and use a proper SMPS drive chip to do current mode control, like LM5022. This avoids a lot of troubles of trying to use 555 and adding more circuits to fix shortcomings.
Boost = flyback architecture means you don't need so extreme a turns ratio and you also get regulation. David
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17th Mar 2023, 11:13 pm | #3 |
Nonode
Join Date: Oct 2010
Location: Tintinara, South Australia, Australia
Posts: 2,324
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Re: foStep up transformer from 9v to 575 volts r a Geiger tube
"If" you can find one of those old disposable film cameras, the flash unit out of them can be easily modified for use and as a bonus, works off a 1.5V battery.
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19th Mar 2023, 8:36 pm | #4 |
Heptode
Join Date: Jul 2018
Location: Worthing, West Sussex, UK.
Posts: 983
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
Look up "Boost converter" and use a proper SMPS drive chip to do current mode control, like LM5022. This avoids a lot of troubles of trying to use 555 and adding more circuits to fix shortcomings.
Boost = flyback architecture means you don't need so extreme a turns ratio and you also get regulation. David Thanks, I am investigating that route. It is new tech for me, I have researched on the net and see endless info. much of which is a bit iffy, but I shall have to bite the bullet and try it. I get the jist of how it works using PWM, but like everything new, go slowly and learn, those chips are not overly cheap so will try to avoid any mistakes. The Geiger Muller tube needs a set voltage to work efficiently, within the plateau or Geiger region, this is all new ground for me- but great fun. Re the 555 idea, The chances of getting a bias transformer from a reel-to-reel bias oscillator or similar seem very slim anyway.
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"Behind every crowd, there's a silver Moonshine" Last edited by Cruisin Marine; 19th Mar 2023 at 8:58 pm. |
19th Mar 2023, 10:02 pm | #5 |
Dekatron
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 8,173
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
Hi, plenty of pot cores available on ebay. Ideally get one with a 4 section bobbin to reduce self capacitance and give better insulation
A 30mm dia or greater type should give sufficient space for your windings Ed |
19th Mar 2023, 10:25 pm | #6 |
Heptode
Join Date: Jul 2018
Location: Worthing, West Sussex, UK.
Posts: 983
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
Can you please link to a relevant one please Ed?
Thanks
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19th Mar 2023, 10:37 pm | #7 |
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
I bought a geiger counter kit from Bull Electrical back in the mists of time.
It uses a transistor multivibrator driving some iron cored transformer followed by a voltage multiplier. The geiger tube is tiny and windowless so if it clicks you know something quite significant hit it. It detects some uranium glass quite well and the I-131 treatment my late mother had sent it crazy even through a wall. The tube runs at about 350 - 400V. On the other hand, the GM4 geiger tube requires 1500V plus. It worked quite well connected to a Tek curve tracer about 40 years ago. The pulses were quite visible on the screen. |
20th Mar 2023, 12:38 am | #8 |
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
A few hints:
Be careful about internet advice. In a fair proportion of cases it amounts to the blind leading the blind. Not all, but you almost need enough knowledge to be able to do the job yourself in order to spot the clueless. National Semiconductor (now part of Texas Instruments) and Linear Technology inc (Now part of Analog Devices inc) Wrote excellent applications notes on these sorts of circuits. They take new users by the hand and lead gently. The LT ones , many of them were written by the legendary Jim Williams are worth reading even if you aren't using their parts. Often, inductors may be available from Coil Craft inc. They have a place near Cumbernald and if contacted via their website, are known to give the occasional (one-off) part to hobbyists as a free sample. Their parts are excellent, their service is excellent, but they are also friendly and encouraging. David
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20th Mar 2023, 11:05 am | #9 |
Triode
Join Date: Feb 2014
Location: London, UK.
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
I've put together a geiger counter twice. The first time I used a reversed 9V mains transformer followed by a voltage doubler as in this video:
https://www.youtube.com/watch?v=8zM1HG9Agzk The second time I used a reversed AF driver transformer from an old transistor radio followed by a 7 stage Cockcroft-Walton multiplier. The frequency applied to the transformer was around 15 kHz in the second case. Tim
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20th Mar 2023, 3:13 pm | #10 |
Dekatron
Join Date: Jan 2003
Location: Bradford on Avon, Wiltshire, UK.
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
You might be able to use the gubbins from one of those fly killer tennis racquet things they sell in the pound shops. Because I’m a nerd I measured the voltage of one for curiosity and found it was several hundred volts.
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20th Mar 2023, 8:05 pm | #11 |
Heptode
Join Date: Jul 2018
Location: Worthing, West Sussex, UK.
Posts: 983
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
I got a very cheap camera flash unit made by Jessops today in a charity shop. It has a transformer driven by two 2SA1242 PNP devices, I need to do some tracing to see how they are driven. It works fine (or did before I dismantled it all). Hopefully I am sorted now.
Thanks to all, especially Tim for the interesting video, nice to know which sources can be used to test the Geiger. I wonder if that Uranium glass or porcelain is still easily available?
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"Behind every crowd, there's a silver Moonshine" Last edited by Cruisin Marine; 20th Mar 2023 at 8:15 pm. |
20th Mar 2023, 9:26 pm | #12 |
Nonode
Join Date: Jan 2010
Location: North Somerset, UK.
Posts: 2,129
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
A useful test source is an old stock pressure lamp mantle. Newer production might be non radioactive but older ones contain radioactive thorium.
"Uranium glass" has come to mean a style of glassware that may not contain any actual uranium. Genuine antique uranium glass can be a useful test source, but modern production may not be. |
20th Mar 2023, 10:09 pm | #13 |
Dekatron
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
Hi Presently away from home, but try looking for Pot cores on ebay. Ideally you want a new one, but cheap older ones can be stripped. Mullard made them in a variety of sizes up to 45mm and on a range od ue grades (higher ue/ lower turns needed)
An inductor core normally has an airgap(possibly with an adjuster); a transformer core is ungapped (but can easily be gapped). Transformer types are used with push pull drivers, rather like with audio amps. David (RW's) warning is very valid there is now a huge amount of crap out there on various social media sites Ed |
21st Mar 2023, 12:36 am | #14 |
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
I'd forgotten about the lamp mantle so beloved of the Late Nuclear Boyscout: I have a fairly old camping gaz lamp with a mantle, that makes the geiger click too.
As I understand it the thorium has been removed from more modern examples. I cobbled together an inverter for the GM4 tube using a large prewound pot core with some added thick primary winding. Worked a treat driven by a big fat MosPower pulsed at 1kHz or so though I doubt if it would last long before the insulation on the secondary failed. |
22nd Mar 2023, 11:46 pm | #15 |
Heptode
Join Date: Jul 2018
Location: Worthing, West Sussex, UK.
Posts: 983
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
I am researching this still and getting further and further.... but, one aspect I don't know the answer to is - can the Geiger Muller tube be used in a screened aluminium box? Or should it be plastic?
A dumb question maybe, but one that I have to ask. I don't intend to have a remote sensor, all built in one box. Thanks.
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23rd Mar 2023, 12:18 am | #16 |
Triode
Join Date: Feb 2014
Location: London, UK.
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
Most Geiger-Muller tubes will detect beta and gamma radiation. Some, such as the Mullard MX168, will detect alpha radiation as well. An aluminium sheet will certainly stop alpha radiation but beta radiation can penetrate thin aluminium. Gamma radiation will penetrate aluminium sheet.
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23rd Mar 2023, 7:39 pm | #17 |
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
Goodness me, beta particles can penetrate 3cm of aluminium.
I didn't know that. As against 1mm of lead. |
23rd Mar 2023, 11:44 pm | #18 | |
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
Quote:
Some WWII photoreconnaissance lenses used lenses doped for anomalous refractive index and the dopant was a radioactive salt For added fun the 'hot' element was often the front one and the glass was slightly water-soluble! Do not clean by licking! This stuff after the war turned up in some specialist telephoto lenses as well... until it was thought better to leave this technology behind. David
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24th Mar 2023, 2:32 am | #19 |
Nonode
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
One of these any good?
https://www.ebay.co.uk/itm/115274062...mis&media=COPY . . .They appear to give about the right sort of h.t. voltage for a G.M. tube off a 3–5V supply, and you can always add a 78L33 or 78L05, or an LM317 circuit with a 240 Ω & a 1k preset, between your battery supply and this module to give your desired output! Chris Williams
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24th Mar 2023, 10:44 am | #20 |
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Re: Step up transformer from 9 to 575 volts for a Geiger tube.
Just dug out a Griffin & George geiger counter with a Mullard GM tube.
The background count is low, a count every 5 seconds or so. The uranium glass doubles or trebles the count. The mantle in the camping gaz lamp is hot compared with the uranium glass. The mantle in the Lidl gas lamp is as inert as expected. |