I am building an experimental radiation detector. Being an experiment, I want to avoid buying anything for it. Sort of a junkbox project to see what could be done using the parts I have. The geiger muler tubes I have require 400 volts. I could do it easily buy buying 200 volt zener diodes and put two in series. Or I could buy a 400 volt gas discharge tube from a Soviet geiger counter cheaply. But I have neither. What I do have is 50 NE2 bulbs with resitors. Could I use those? It would probably take 5 or 6 in series to do it, which compared to two 5 cent zeners from eBay seems like a waste of money and circuit board real estate, but I am looking to do something that does not require me to order anything from anyone. TIA Geoff -- Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379
Using NE2 bulbs as voltage regulators
Started by ●August 9, 2015
Reply by ●August 9, 20152015-08-09
On Sunday, 9 August 2015 05:49:07 UTC+1, Geoffrey S. Mendelson wrote:> I am building an experimental radiation detector. Being an experiment, I > want to avoid buying anything for it. Sort of a junkbox project to see > what could be done using the parts I have. > > The geiger muler tubes I have require 400 volts. I could do it easily buy > buying 200 volt zener diodes and put two in series. Or I could buy a 400 > volt gas discharge tube from a Soviet geiger counter cheaply. > > But I have neither. > > What I do have is 50 NE2 bulbs with resitors. Could I use those? > > It would probably take 5 or 6 in series to do it, which compared to two > 5 cent zeners from eBay seems like a waste of money and circuit board real > estate, but I am looking to do something that does not require me to > order anything from anyone.Neons wre used as volt reg references in the valve days. Just beware that V is far higher until it strikes, so your following stage should ramp up. And keep the neon in the dark to avoid erratics. And keep current down to avoid failure. And smooth their output well, they get get a bit messy years down the line. NT
Reply by ●August 9, 20152015-08-09
On Sunday, 9 August 2015 06:44:17 UTC+1, tabb...@gmail.com wrote:> On Sunday, 9 August 2015 05:49:07 UTC+1, Geoffrey S. Mendelson wrote: > > I am building an experimental radiation detector. Being an experiment, I > > want to avoid buying anything for it. Sort of a junkbox project to see > > what could be done using the parts I have. > > > > The geiger muler tubes I have require 400 volts. I could do it easily buy > > buying 200 volt zener diodes and put two in series. Or I could buy a 400 > > volt gas discharge tube from a Soviet geiger counter cheaply. > > > > But I have neither. > > > > What I do have is 50 NE2 bulbs with resitors. Could I use those? > > > > It would probably take 5 or 6 in series to do it, which compared to two > > 5 cent zeners from eBay seems like a waste of money and circuit board real > > estate, but I am looking to do something that does not require me to > > order anything from anyone. > > Neons wre used as volt reg references in the valve days. Just beware that V is far higher until it strikes, so your following stage should ramp up. And keep the neon in the dark to avoid erratics. And keep current down to avoid failure. And smooth their output well, they get get a bit messy years down the line.Voltage overshoot could maybe be reduced wth high R resistors from V_in_+ to various points in the neon chain. NT
Reply by ●August 9, 20152015-08-09
On Sunday, 9 August 2015 14:49:07 UTC+10, Geoffrey S. Mendelson wrote:> I am building an experimental radiation detector. Being an experiment, I > want to avoid buying anything for it. Sort of a junkbox project to see > what could be done using the parts I have. > > The geiger muler tubes I have require 400 volts. I could do it easily buy > buying 200 volt zener diodes and put two in series. Or I could buy a 400 > volt gas discharge tube from a Soviet geiger counter cheaply. > > But I have neither. > > What I do have is 50 NE2 bulbs with resistors. Could I use those? > > It would probably take 5 or 6 in series to do it, which compared to two > 5 cent zeners from eBay seems like a waste of money and circuit board real > estate, but I am looking to do something that does not require me to > order anything from anyone.Apparently neon bulbs need 90V to start conducting and settle to about 60V at their rated current. Six or seven of them in series would give you 360V or 420V. You'd need better than 630V to drive a seven lamp string into conduction, and your series resistor would be dropping 210V after they'd turned on. 100uA should be enough current to keep them glowing, so the resistor would have to dissipate at least 20mW, which should not be a problem. Getting the extra 200V might be a pest. http://www.bristolwatch.com/ele/neon.htm Zener diodes don't need extra voltage to get them conducting, but you do need enough voltage headroom to cope with their temperature dependence - about 0.13% per degree Kelvin - about 5% over the 40C "room temperature range" or 21V in your 400V, on top of the +/-5% tolerance - another 20V - on the zener voltage. The data sheets typically use 5mA tests currents (which is high - 10W - for a 200V part). The 3W Motorola 1N5956B http://www.farnell.com/datasheets/112148.pdf at least specifies the zener impedance at 0.25mA and shows a plot of voltage versus current. You'd still need about 20V headroom above the worst case 440V for a simple series resistor based shunt regulator. You could do better with a PNP constant current source to provide a constant current through the Zener string, which would work fine with only only a few volts of extra headroom. -- Bill Sloman, Sydney
Reply by ●August 9, 20152015-08-09
Ever see the designof alotof 1990s DC regulators ? they use a Zener with a voltsage divided down reference. I you want to stick with tubes, a constant current source is not all that hard. you could make one neon cancel out the other actually. From there it is a simple feedback circuit. I could do it, IF I understand what you want properly. One thing though, I owuld suggest a lead cage for the neons and any other sensitive tubes. you might geet away with steel actually if you don't go digging around Fukushima, but it depends on how much accuracy you want.
Reply by ●August 9, 20152015-08-09
On Sun, 9 Aug 2015 04:49:03 +0000 (UTC), "Geoffrey S. Mendelson" <gsm@mendelson.com> wrote:>What I do have is 50 NE2 bulbs with resitors. Could I use those? > >It would probably take 5 or 6 in series to do it, which compared to two >5 cent zeners from eBay seems like a waste of money and circuit board real >estate, but I am looking to do something that does not require me to >order anything from anyone.The last time I tried to use a neon lamp as a voltage regulator, I managed to build to perfectly functional relaxation oscillator instead. Try googling for a GM power supply schematic: <https://www.google.com/search?tbm=isch&q=geiger+counter+power+supply+schematic> See any that use neon lamp regulators? That should be a clue. My antique CDV-900 counter uses a 900v regulator tube made by Victoreen. <http://www.logwell.com/tech/dhdwe/HV_woes.html> <http://www.logwell.com/products/Codatron_Corotron.html> There's a difference between these and neon lamps, but I don't recall the details. The designer of these replacements is someone that posts regularly to this newsgroup. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Reply by ●August 9, 20152015-08-09
Sure, but why? Where are you generating the voltage from in the first place? If it's from a big iron transformer and rectifier, or a hand-cranked leather and glass apparatus... it's probably a good idea to regulate (or at least filter heavily)! If you're starting with battery power, you're much better off using an SMPS, and throttling that. Don't fight a dirty supply, bend it to your will and make it work for you. As for the bulb themselves, they're kind of noisy, and sure to drift (especially over age), but as mentioned, they have been used from time to time, and given their operating envelope, do about as well as you'd expect. There were some varieties that were specially selected or formulated or aged, if you wanted something smaller than a proper 0A3 or 0G3*. I'm guessing this isn't important in this case, as your pile of junk-box bulbs probably isn't the fancy kind. *0G3 was the precision zener of its day, doing about 0.5% stability and 600nV/rtHz noise -- volt per volt, quieter than a TL431. Tim -- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com "Geoffrey S. Mendelson" <gsm@mendelson.com> wrote in message news:slrnmsdml7.eis.gsm@cable.mendelson.com...>I am building an experimental radiation detector. Being an experiment, I > want to avoid buying anything for it. Sort of a junkbox project to see > what could be done using the parts I have. > > The geiger muler tubes I have require 400 volts. I could do it easily buy > buying 200 volt zener diodes and put two in series. Or I could buy a 400 > volt gas discharge tube from a Soviet geiger counter cheaply. > > But I have neither. > > What I do have is 50 NE2 bulbs with resitors. Could I use those? > > It would probably take 5 or 6 in series to do it, which compared to two > 5 cent zeners from eBay seems like a waste of money and circuit board real > estate, but I am looking to do something that does not require me to > order anything from anyone. > > TIA > > Geoff > > -- > Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379 >
Reply by ●August 9, 20152015-08-09
Bill Sloman wrote:> On Sunday, 9 August 2015 14:49:07 UTC+10, Geoffrey S. Mendelson wrote: >> I am building an experimental radiation detector. Being an experiment, I >> want to avoid buying anything for it. Sort of a junkbox project to see >> what could be done using the parts I have. >> >> The geiger muler tubes I have require 400 volts. I could do it easily buy >> buying 200 volt zener diodes and put two in series. Or I could buy a 400 >> volt gas discharge tube from a Soviet geiger counter cheaply. >> >> But I have neither. >> >> What I do have is 50 NE2 bulbs with resistors. Could I use those? >> >> It would probably take 5 or 6 in series to do it, which compared to two >> 5 cent zeners from eBay seems like a waste of money and circuit board real >> estate, but I am looking to do something that does not require me to >> order anything from anyone. > > Apparently neon bulbs need 90V to start conducting and settle to about 60V at their rated current. Six or seven of them in series would give you 360V or 420V. You'd need better than 630V to drive a seven lamp string into conduction, and your series resistor would be dropping 210V after they'd turned on. 100uA should be enough current to keep them glowing, so the resistor would have to dissipate at least 20mW, which should not be a problem. Getting the extra 200V might be a pest. > > http://www.bristolwatch.com/ele/neon.htm > > Zener diodes don't need extra voltage to get them conducting, but you do need enough voltage headroom to cope with their temperature dependence - about 0.13% per degree Kelvin - about 5% over the 40C "room temperature range" or 21V in your 400V, on top of the +/-5% tolerance - another 20V - on the zener voltage. The data sheets typically use 5mA tests currents (which is high - 10W - for a 200V part). The 3W Motorola 1N5956B > > http://www.farnell.com/datasheets/112148.pdf > > at least specifies the zener impedance at 0.25mA and shows a plot of voltage versus current. > > You'd still need about 20V headroom above the worst case 440V for a simple series resistor based shunt regulator. You could do better with a PNP constant current source to provide a constant current through the Zener string, which would work fine with only only a few volts of extra headroom. >All of these schemes mentioned are rather noisy; unless one uses a large current thru those zeners,they will be very noisy (look like they are oscillating). If you can afford it,how about a regulator that is quiet from 1uA to 1mA (beyond spec current). Available in 50V steps from 50V up to a few KV.
Reply by ●August 9, 20152015-08-09
Jeff Liebermann wrote:> On Sun, 9 Aug 2015 04:49:03 +0000 (UTC), "Geoffrey S. Mendelson" > <gsm@mendelson.com> wrote: > >> What I do have is 50 NE2 bulbs with resitors. Could I use those? >> >> It would probably take 5 or 6 in series to do it, which compared to two >> 5 cent zeners from eBay seems like a waste of money and circuit board real >> estate, but I am looking to do something that does not require me to >> order anything from anyone. > > The last time I tried to use a neon lamp as a voltage regulator, I > managed to build to perfectly functional relaxation oscillator > instead. Try googling for a GM power supply schematic: > <https://www.google.com/search?tbm=isch&q=geiger+counter+power+supply+schematic> > See any that use neon lamp regulators? That should be a clue. > > My antique CDV-900 counter uses a 900v regulator tube made by > Victoreen. > <http://www.logwell.com/tech/dhdwe/HV_woes.html> > <http://www.logwell.com/products/Codatron_Corotron.html> > There's a difference between these and neon lamps, but I don't recall > the details. The designer of these replacements is someone that posts > regularly to this newsgroup. > > > > > >Yes; i just mentioned that the Codatron(R) is very quiet and available in 50V steps from 50V.
Reply by ●August 9, 20152015-08-09
