Good to hear - another successful neon spinny thing!
Jon.
On Wednesday, February 17, 2021 at 10:55:59 PM UTC bung...@gmail.com wrote:
> I tried my new circuit with the optocouplers using 270k for R5 & R6 and 1k
> for R3 & R4.
> It works within the limits of +0v and about -22v. It is interesting that
> the other circuit did not work for low + bias. It must be the slower
> positive edge as someone mentioned. I will use about +30 and -30v, whatever
> the rectified transformer gives.
> This is my preliminary software. It only counts up at present from 0 to 9
> fast (10Hz) slowing down to 1Hz then repeating. The delay between the
> steering pulses depends on the speed so at 1 Hz you can actually see every
> pin lit. I thought it a waste to not see them. I have not fully tried this
> software, only a Dekatron test version, so if there are errors please
> forgive me. There is a BCD version that also works. I may add a "Spinner"
> between 0 to 9 counts in place of the 2 second delay, 1 second forwards and
> 1 second backwards.
> // main loop
> while (1) // loop endlessly
> {
> for(j=1;j<=10;j++) // sets the delays
> {
> for(i=0;i<=9;i++) // the BCD digit displayed (Nixies, etc)
> {
> // generate clock and BCD
> output_high(pin_C4); // high for 10 uS
> delay_us(10);
> output_low (pin_C4); // end pulse
> portC = i; // output BCD
> // Dekatron clocking
> output_high(pin_A5); // steering ring 1
> delay_ms(j*50);
> output_high(pin_A4); // steering ring 2
> delay_ms(j*50);
> output_low (pin_A5);
> delay_ms(j*50);
> output_low (pin_A4);
> // period of sequence
> delay_ms(j*100); // set period
> } //end for i loop
> delay_ms(2000); // wait 2 seconds after each 0 to 9 count
> } //end for j loop
> } //end of endless while loop
> } // end of main function
>
> On Wed, Feb 17, 2021 at 4:00 PM Jon <deka...@nomotron.com> wrote:
>
>> No hard figures - it's dependent on a bunch of factors; principally
>> manufacturing quality, how you use the tube, operating temperature and gas
>> fill. If you keep the operating current within spec and preferably at the
>> lower end, avoid the tube getting heated from its surroundings and above
>> all else keep the glow moving around all of the electrodes, they will last
>> a seriously long time. The electrical properties will change gradually -
>> the maintaining voltage rises and the latitude around the voltages required
>> for reliable stepping decreases. So you were absolutely right to point out
>> the importance of taking note of these elements of the spec when designing
>> - you can get away with a lot on a NIB tube, but progressively less with
>> age. Of course if the application requires clear glass to see the lovely
>> glow, then the tube may reach end of its useful life in that application as
>> sputtering gradually obscures the view, and that may happen well before it
>> ceases to step reliably.
>>
>> I'm not surprised by gregebert's description of his A101 - his
>> application sounds like a great recipe for a long dekatron life. The slow
>> speed ones are tough as anything and they love to work! Just for context, I
>> believe that the large majority of dekatrons working in the stores of the
>> WITCH today are from the original complement of tubes the machine was built
>> with at the start of the 1950s. Can't formally prove it of course, but the
>> date codes are consistent with that. Also, as we've noted before on other
>> Russian glow tubes, the guaranteed life spans on the datasheets are
>> ridiculously conservative if the tubes are treated well. The A101 datasheet
>> gives a 1000 hour life - his A101 has done 70x that! I have a similar
>> experience with my IN9 clock - the prototype unit is still going strong on
>> its original tubes after 120K hours - datasheet life is 1K hours.
>>
>> Note that we're talking here about use-related life limitation - the
>> death in storage of the high-speed dekatrons is a whole different topic.
>>
>> Jon.
>>
>> On Tuesday, February 16, 2021 at 8:49:07 PM UTC Dekatron42 wrote:
>>
>>> No, unfortunately not, no hard figures - maybe Jon has. I've only read
>>> in some books about dekatron construction (neon tube construction in
>>> general where dekatrons are shown as special variations) that they have
>>> similar lifespans compared to small neon lamps but that the complex design
>>> complicates the failure modes/rate and also that keeping currents/voltages
>>> within the values specified in the datasheet will guarantee that they work
>>> as long as possible.
>>>
>>> It depends on when you say a dekatron fails, it can get a silvery finish
>>> on the glass so you almost can't see the glow but it still works and it can
>>> fail a lot earlier than that due to internal flash-overs due to sputtering
>>> onto the ceramic material which means a current can flow in this sputtered
>>> material as the distance is shorter there compared to other paths (I have a
>>> few dekatrons with that failure and of course a few with a silvery look).
>>>
>>> I have to count my dekatrons one day to see if I have enough to build a
>>> second Harwell WITCH..... ;) :)
>>>
>>> /Martin
>>>
>>> On Tuesday, 16 February 2021 at 17:16:07 UTC+1 gregebert wrote:
>>>
>>>> *Martin* - Do you know how long dekatrons last ? I have an A-101
>>>> running as a spinner in one of my clocks, and it's been going 60RPM 24/7
>>>> for almost 8 years with no signs of degradation. I use 30k dropping
>>>> resistors at the cathodes, and the current is right at the spec value of
>>>> 450uA, so that gives about 15V for "steering", and the driving waveform is
>>>> 3-phase with overlap. I
>>>>
>>>> On Tuesday, February 16, 2021 at 4:15:05 AM UTC-8 Dekatron42 wrote:
>>>>
>>>>> There is one more dimension to think about when running a dekatron and
>>>>> that is that over time it will degrade due to sputtering affecting the
>>>>> electrodes and to maintain a correct counting when it ages you should
>>>>> keep
>>>>> the voltages as described in the datasheet, especially the guide and bias
>>>>> voltages as those are needed when the dekatron nears its end of life - it
>>>>> is the same effect that is in play if you want to raise a dekatron from
>>>>> the
>>>>> dead if it has been heavily used or just stored for a very long time
>>>>> without use, raise the bias/pulse voltages and sometimes the anode
>>>>> voltage
>>>>> to surpass the effects of the sputtering - effectively increasing the
>>>>> current flow between the anode and the guides/cathodes.
>>>>>
>>>>> So even if dekatrons work at other voltages you will see the effects
>>>>> of lower/incorrect voltages when they near their end of life, this has
>>>>> been
>>>>> described in older litterature where the internals of dekatrons has been
>>>>> disected in detail - you might just need some 10V below the glowing
>>>>> cathode
>>>>> to move the glow on a new dekatron but as it ages it will stop working at
>>>>> that voltage.
>>>>>
>>>>> /Martin
>>>>>
>>>>> On Tuesday, 16 February 2021 at 00:53:36 UTC+1 bung...@gmail.com
>>>>> wrote:
>>>>>
>>>>>> Those values were left over from the 5v circuit. I was more concerned
>>>>>> with the level shifting from the PIC at 0 to +5v.
>>>>>> Peter
>>>>>>
>>>>>> On Mon, Feb 15, 2021 at 6:48 PM Jon <deka...@nomotron.com> wrote:
>>>>>>
>>>>>>> I'd had a similar thought about increasing the bias resistors - it's
>>>>>>> not necessary to run so much current (5mA) through that part of the
>>>>>>> circuit.
>>>>>>>
>>>>>>> OK, so your proposed conditions are that the dekatron will see are
>>>>>>> 400V anode to main cathodes; guides swinging from +25V to -25V with
>>>>>>> respect
>>>>>>> to main cathodes. Tube current will be about 345uA.
>>>>>>> I've replicated these on my dekatron tester using a nice NIB GS10C/S
>>>>>>> as the test subject and can confirm that they do work - the tube
>>>>>>> stepped
>>>>>>> fine up at speeds up to over 4kpps once I'd woken it up a bit.
>>>>>>>
>>>>>>> Caveats:
>>>>>>> 1) I only tried one tube.
>>>>>>> 2) My circuit is rather different to yours so although the static
>>>>>>> voltages are the same, the pulse shapes are almost certainly different.
>>>>>>> And
>>>>>>> we didn't even talk yet about pulse durations, so I've no idea what
>>>>>>> your
>>>>>>> PIC is spitting out. But as long as you're not trying to cut things too
>>>>>>> fine, there's lots of latitude to find patterns that work. Keep things
>>>>>>> north of 100us per phase and you'll be fine unless you've got a really
>>>>>>> reluctant tube.
>>>>>>> 3) I was running at slightly lower current (300uA) so you've
>>>>>>> probably got a bit more margin for speed than I had. Recommended
>>>>>>> operating
>>>>>>> conditions are 325uA +/- 20%, so we're both inside that range. But a
>>>>>>> little
>>>>>>> more rather than less current is useful when pushing higher speeds. I'm
>>>>>>> guessing though that you're looking for a much slower stepping speed
>>>>>>> for
>>>>>>> this application though.
>>>>>>>
>>>>>>> If you've not already done so, I'd definitely second Martin's
>>>>>>> recommendation to take a look at Michael Moorrees' dekatron work (he
>>>>>>> looks
>>>>>>> in here from time to time too). He used a couple of elegant design
>>>>>>> tricks
>>>>>>> which simplify the interfacing of dekatrons to modern electronics /
>>>>>>> microcontrollers - I've followed his approach in pretty much all the
>>>>>>> stuff
>>>>>>> I've built and it works a treat. Not to say that other approaches
>>>>>>> aren't
>>>>>>> equally useful too of course.
>>>>>>>
>>>>>>> Jon.
>>>>>>>
>>>>>>> On Monday, February 15, 2021 at 9:39:13 AM UTC Dekatron42 wrote:
>>>>>>>
>>>>>>>> I'd raise the resistance to at least some 100k for the two bias
>>>>>>>> resistors R5 & R6 in your diagram above.
>>>>>>>>
>>>>>>>> I'd also use the correct bias voltage and just use an MPSA42 with
>>>>>>>> its emitter to common ground for the driver to simplify the circuit as
>>>>>>>> Ronald Dekker and Michael Moorrees with their dekatron circuits.
>>>>>>>>
>>>>>>>> Different dekatrons need different bias and pulse voltages on the
>>>>>>>> guide electrodes to count properly so accomodating for those
>>>>>>>> requiremenst
>>>>>>>> will remove a lot of problems and keep down the fault finding time.
>>>>>>>>
>>>>>>>> /Martin
>>>>>>>> On Monday, 15 February 2021 at 03:05:12 UTC+1 bung...@gmail.com
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> You are absolutely right. 5v was not high enough despite Ronald's
>>>>>>>>> and my confirmation that it would work.
>>>>>>>>> I am changing to +25v and -25v and will have an optocoupler with
>>>>>>>>> the diode driven from the 5v PIC and the transistor at the bottom of
>>>>>>>>> the
>>>>>>>>> resistor between the two power supplies. It keeps it simple. I have
>>>>>>>>> to
>>>>>>>>> order the optocoupler because none of my old ones have higher than 30
>>>>>>>>> v
>>>>>>>>> rating.
>>>>>>>>> I will have to think about the extra two power supplies. Maybe I
>>>>>>>>> can't avoid them. It will be a few days until I get the parts.
>>>>>>>>> Peter
>>>>>>>>> [image: Dekatron Circuit.jpg]
>>>>>>>>>
>>>>>>>>> On Sun, Feb 14, 2021 at 3:18 PM Jon <deka...@nomotron.com> wrote:
>>>>>>>>>
>>>>>>>>>> Interesting approach - not seen it rigged up quite like that. Let
>>>>>>>>>> us know how it goes!
>>>>>>>>>>
>>>>>>>>>> My immediate question is whether there's a big enough potential
>>>>>>>>>> difference between an inactive guide and a main cathode to get a
>>>>>>>>>> reliable
>>>>>>>>>> transfer forward from a deactivating G2 to the 'next' main cathode
>>>>>>>>>> rather
>>>>>>>>>> than back to the adjacent recently used G1 - 5V is much lower than
>>>>>>>>>> the
>>>>>>>>>> datasheet guide bias. Might be OK at slow stepping speeds with long
>>>>>>>>>> guide
>>>>>>>>>> pulses. Also the leading edge of your guide pulses is going to be
>>>>>>>>>> fairly
>>>>>>>>>> slow as Q1/2 come out of saturation and the guides are passively
>>>>>>>>>> pulled
>>>>>>>>>> down to the 'active' voltage. Most guide drive circuits use a NPN
>>>>>>>>>> pull-down
>>>>>>>>>> to the active state which creates a sharp leading edge and then a
>>>>>>>>>> slower
>>>>>>>>>> return to the inactive state.
>>>>>>>>>>
>>>>>>>>>> Jon.
>>>>>>>>>>
>>>>>>>>>> On Sunday, February 14, 2021 at 7:06:28 PM UTC bung...@gmail.com
>>>>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>>> Having finished the Amperex 8453 display I started on my
>>>>>>>>>>> Dekatron. Thanks to all for the suggestions.
>>>>>>>>>>> I read up on Ronald Dekker's clock project
>>>>>>>>>>> https://www.dos4ever.com/decatron/decatronweb.html
>>>>>>>>>>> and decided against a direct drive from a 74141 because, even
>>>>>>>>>>> if it was practical, it would not look as good as using all the
>>>>>>>>>>> pins. It
>>>>>>>>>>> would look like the 8453 I just finished except without the number
>>>>>>>>>>> mask.
>>>>>>>>>>> A few quick experiments showed that a -24v power supply was
>>>>>>>>>>> needed for the easiest implementation.. This is my design. I will
>>>>>>>>>>> let you
>>>>>>>>>>> know if it works.
>>>>>>>>>>>
>>>>>>>>>>> A PIC drives the circuit: it starts with Q3 off to force a start
>>>>>>>>>>> at 1. A high on R3 or R4 is the same as the switches in Ron's test
>>>>>>>>>>> circuit
>>>>>>>>>>> placing -24v on the guides. As my PIC sends the BCD for the other
>>>>>>>>>>> displays
>>>>>>>>>>> and clocks the E1T it will generate the sequence to advance or
>>>>>>>>>>> retard this
>>>>>>>>>>> Dekatron..
>>>>>>>>>>> [image: Dekatron Circuit.jpg]
>>>>>>>>>>>
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