Interesting happenings with neon ring counter

Discussion in 'General Electronics Chat' started by magnet18, Feb 1, 2011.

  1. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Hi everyone,
    A few nights ago I threw together a simple neon ring counter with some parts I had lying around

    After experimenting for a couple minuets I got it to work with a SPDT switch and some 50V caps I scavenged

    theres a video of it on youtube here, my question is, i thought they were only supposed to trigger on a positive input pulse, but with mine it triggers both when i make the capacitors high (180V), and when i make them low (0V)

    I have some ideas in my head as to why this is, but i really don't know, and was wondering if anyone else did

    In addition to this, I was messing around and when increased the lower resistors enough the tubes began triggering themselves, I believe this to be because enough of a negative charge is building up on the capacitor that it forces the next tube to light, but I was wondering if this assumption would be correct

    And finally, when I added another resistor in parallel to the large bottom ones when it was self triggering, the tubes all began flickering almost too fast to perceive and i heard a loud buzz like an angry wasp, i didn't mess with this for fear of damaging something, but i was wondering why it was happening

    I realize this is a long post, thanks for reading it and thanks in advance for explaining things :)
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Something doesn't look right. I don't think the original design used diodes.

    The neon bulb is a switch, it hits 60V, starts conducting, and drops to 20V as it discharges the capacitor. At around 20V it stops conducting (goes out), and becomes an open switch again.

    Here is what I remember...

    http://analogouslyspeaking.blogspot.com/2009/06/neon-oscillators.html
     
  3. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Bill, youre thinking the multivibrator you pointed out to me
    i built a variation of this
    [​IMG]
    off of this site :)
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    Ah. OK. Other than a quick study in high school around 197<mumble>. I suspect you are way ahead of me on the game.

    I see how it is supposed to work, the diode only allow current to flow one way, and steer which component goes off next.

    The neon triggers off of 60V as I recall. One conducting it will stay on with as little as 20V (this keeps gas ionized). The exact current is not important, it can be quite low. In some ways a neon is similar to an LED, in a mirror sort of way. It is a voltage fired device, the current keeps the gas ionized, but drop below the critical voltage (20V) it stops conducting until it is fired with 60V again.

    Try using a voltage divider to drop the power supply. I suspect you are swamping everything out. A neon with more than 60V across it will fire, and drop to 20V (across the neon). You don't need current here, just a stable voltage. This is where a stock of meg ohm resistors come in handy.
     
  5. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    90V and 45V for these actually
    doing some maths the most current these could see is about 1.15 with what i have, which is well within their ratings

    but im not concerned about making this work, it has no purpose and i know how it works if i follow the directions

    i want to know why it does what it does when i do stuff to it that i shouldn't :)

    Im looking for answers about the theory of why the next one fires when i connect c4 to ground, if i was right in my assumption about the glow transferring by itsself when the bottom resistors are really large, and why a scary buzzing sound was made when 2 resistors were connected in parallel
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Think in terms of voltages. When you connect a point to ground, where is the high(est) voltage going to be.
     
  7. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    so when i connect the capacitors to ground, they "suck away" all available positive charge?
    I think i get it :)
     
    Last edited: Feb 1, 2011
  8. Wendy

    Moderator

    Mar 24, 2008
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    With the diodes, there can be only one capacitor that is charged up, the others are lagging behind, they can't charge over the maximum voltage until their diode is back biased. This is why you have a starter injection point. You keep this up I may have to buy the parts and try it out, it is interesting stuff. It looks like a protoboard would work with it.

    Where did you get your DC/DC converter?
     
  9. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Same converter one im using for my nixie clock

    And by "capacitors" i meant the ones im using in parallel, between the switch and the neon's positive

    I know only one capacitor is charged, when you get a chance, read through Ronald's page, it explains it in great detail (this seems backwards here:))

    it is pretty interesting, and if you look at the video, im using a protoboard (unless that is something different than a bread board

    Its like digital signal division using neon, if i ever get my current clock done i might make one using this principle :)
     
  10. nomurphy

    AAC Fanatic!

    Aug 8, 2005
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    Here's a random flasher version:
     
  11. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    interesting, looks like the capacitors are being used to extinguish their own neon
     
  12. bitrex

    Member

    Dec 13, 2009
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    I have a great PDF copy of a 1966 GE book called the "Glow Lamp Manual" that has a ton of glow lamp circuits, including ring counters and glow lamp logic. Unfortunately I don't think I'll post it here as due to the absurd copyright extension laws here in the U.S. it won't enter the public domain until sometime around 2063. However, If you do a Google Search for "Glow Lamp Manual filetype : pdf" it should be the first result.
     
  13. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Thanks :)
    im guessing no-one on here knows off the top of their heads why the buzzing occurred though?
     
  14. Wendy

    Moderator

    Mar 24, 2008
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    Where is the source? I suspect your DC/DC converter first, as it uses AC to feed a transformer or buck boost circuit (which have inductors).
     
  15. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    I dont know, it might have been a specific resistance combined with the dc-dc converter, or it might have to do with having resistors in parallel on each neon, as that was the only time it happened
     
  16. Audioguru

    New Member

    Dec 20, 2007
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    I made a few Neon bulb chaser circuits 50 years ago and cast them in clear plastic. They chased around and around for about 1 hour then got all mixed up for the next hour. Then the 3rd hour they chased normally again.

    I used a 90V battery. One of them blew up because I forgot to add a vent to allow gasses to escape from the battery through the casted plastic.
     
  17. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Last edited: Feb 2, 2011
  18. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    First of all, my simulation works exactly the same with or without C4, which is what I suspected would happen.
    Secondly, even if C4 were necessary, the voltage at the top end of your neon bulb will be independent of where the other end of the capacitor is connected.
     
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