RE: [neonixie-l] Lighting up a DM160

[judge2005]

Thanks. That got me started finding some more info too. I might be back if I 
don’t get anywhere with the practicalities!

From: Dylan Distasio
Sent: Thursday, March 9, 2017 9:51 PM
To: neonixie-l@googlegroups.com
Subject: Re: [neonixie-l] Lighting up a DM160

Are you asking specifically about how to get the different required voltages in 
practice or what the voltages/current/pinouts are in the first place?

If the latter, this is a pretty well explained datasheet:
http://www.mif.pg.gda.pl/homepages/frank/sheets/009/d/DM160.pdf


On Thu, Mar 9, 2017 at 9:32 PM, Paul Andrews  wrote:
I just impulsively bought some DM160 VFD indicators and now I am at a loss as 
to how to power them! Can anyone help?
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Re: [neonixie-l] Lighting up a DM160

[Dylan Distasio]

Are you asking specifically about how to get the different required
voltages in practice or what the voltages/current/pinouts are in the first
place?

If the latter, this is a pretty well explained datasheet:
http://www.mif.pg.gda.pl/homepages/frank/sheets/009/d/DM160.pdf


On Thu, Mar 9, 2017 at 9:32 PM, Paul Andrews  wrote:

> I just impulsively bought some DM160 VFD indicators and now I am at a loss
> as to how to power them! Can anyone help?
>
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[neonixie-l] Lighting up a DM160

[Paul Andrews]

I just impulsively bought some DM160 VFD indicators and now I am at a loss 
as to how to power them! Can anyone help?

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Re: [neonixie-l] Rookie question about driving VFD filament

[John Rehwinkel]

> Thanks everyone for answers, I will probably use some cheap VFD to test the 
> 9.2% PWM @3,3V on high frequency. I'll measure current and will look on it on 
> oscilloscope to see on which frequency the filament will be heated so 
> frequently, that it won't have time to really cool (current will be flat 
> enough on all ON time). I will also test if any kind of soft-start is needed 
> (rushing 3,3V through cold filament sounds risky).

This is where a series resistor or capacitor comes in handy.  They will limit 
the amount of current allowed to flow through a cold filament.

> I've found one project, where author built a H bridge to be able to imitate 
> AC.

My suggestion of using a MOSFET driver amounts to the same thing (it's not 
original to me, I lifted the idea from Konstantin).

> I think that it might be the way to go, combining H bridging with PWM.

I'm fond of it.  If you use a capacitor as the dropping element, current goes 
to zero if PWM is off, which is an easy way to turn off the filament.

- John

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Re: [neonixie-l] Rookie question about driving VFD filament

[ten kowal]

Thanks everyone for answers, I will probably use some cheap VFD to test the 
9.2% PWM @3,3V on high frequency. I'll measure current and will look on it 
on oscilloscope to see on which frequency the filament will be heated so 
frequently, that it won't have time to really cool (current will be flat 
enough on all ON time). I will also test if any kind of soft-start is 
needed (rushing 3,3V through cold filament sounds risky).
as for the aspect of uneven lightning while PWMing - as far as I understand 
it doesn't change much if I PWM it or not, of course filament-anode voltage 
will be different, but on such a small tube with 50+ anode voltage I doubt 
it will make a change. Also, it definitely won't be visible as left-right 
difference, because in IV-6 filament is a single wire going directly in the 
middle from top to bottom - so depending on connection I can make top or 
bottom a bit dimmer.

I've found one project, where author built a H bridge to be able to imitate 
AC. I think that it might be the way to go, combining H bridging with PWM. 
Definitely gonna try it some day - I must find a lot of cheap VFDs, here in 
my country there is someone offering 100x IV-8 for 30 dollars, I'll 
probably just buy them to have enough "material".
https://callumnunesvaz.wordpress.com/portfolio/dogbonevfd/

W dniu wtorek, 7 marca 2017 18:30:16 UTC+1 użytkownik taylorjpt napisał:
>
> An important aspect of the filament has not been discussed in this 
> thread:  Yes, the filament needs to be heated so that it emits electrons 
> efficiently but it also sets the potential difference between the cathode 
> (Itself) and the anodes (the segments).  For the later reason you can't 
> simply calculate the number of watts and then use a PWM to get to that 
> number.  20% of 5V is technically 1V but that means that one end of the 
> cathode is at 5V potential (for 25% of the time) and the other end is at 
> 0V.  If the anodes are at 30V then the end of the display nearest the PWM 
> will get 28V (anode to cathode) and the end nearest the ground side will 
> get 30V (anode to cathode) or 7% brighter.  This is why filaments, 
> especially for wide multi digit displays, are operated with an AC drive to 
> minimize the end-to-end voltage differential.  For a single digit like the 
> IV-6 this will result in uneven illumination between the left and right 
> side of the display.
>
> Another consideration is the grid to filament bias.  The grid for an "Off" 
> digit is typically held at a negative potential relative to the filament to 
> repel the emitted electrons thus preventing them from hitting the anodes.  
> A grid that is not properly biased this way results in segments that are 
> dimly lit when they should be off because of electrons that sneak through 
> the grid.  This is why the filament is usually biased so that ground is 
> below the lowest voltage of either end of the filament so that grids at 
> ground potential are negative with respect to the filament... or else the 
> grids are operated at a negative voltage for filaments at zero volts.  An 
> IV-6 operated by itself does not need the grid to be used but for a group 
> of them in a multiplexed display this is critical.  If 5 filaments are 
> connected in series to 5V, they will all get 1V but the cathode to anode 
> potential (For a 30V anode voltage) for the one nearest the 5V will be 
> 25.5V (Average) and the one nearest ground will be 0.5V (Average) or a 20% 
> difference in brightness.
>
>
>
>
>

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[neonixie-l] Re: Taylor Edge Nixie Clock Kit

['Terry S' via neonixie-l]

First we need some clarification of the problem, as your original post 
contains a discrepancy. At one point you say the 10 minute tube is not 
counting correctly, then later you say it is fine. This is probably a typo, 
but let's hear the answer.

Nick, the 10s are driven by 92's and the 1s by 90's. Another minor 
correction for clarity.

Here is where I would break out the logic analyzer and hang some probes, 
watch the count sequence. This appears to be a case of the counters not 
resetting properly as they roll over from 5 to 0.  This could be for a 
number of reasons, maybe the parts are faster than the used to be, subtle 
changes in setup & hold times can occur with die changes, shrinks, 
technology changes, etc. Maybe a ringing clock that never used to be a 
problem is now..

USB based logic analyzers are handy tools, and have gotten pretty cheap.

Check the counting with & without the 74141s installed. If they are loading 
the counter outputs, they could affect the count sequence, as some outputs 
are also used internally on the counters to sequence the F/Fs.

Terry


On Wednesday, March 8, 2017 at 9:07:27 PM UTC-6, Nick wrote:
>
> ...Also, reading your problem description isolates the issue to the 10s 
> digits. 
>
> The 10s are driven by 7490s whereas the units are driven by 7492s. Do you 
> have the right chips in the right places?
>
> I'd also try swapping round the 74141s between the 10s and units to see if 
> the problem moves with them - 74141s can fail
>
> Isolate the problem.
>
> Nick
>
>

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Re: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

[David Speck MD]

Along the same line, is there a chance that you have a counterfeit 7490 
chip?  A lot of chips coming from Asia are marginal manufacturing 
rejects or remarked circuit pulls that may have been mid-labeled.


Dave


On 3/9/2017 4:21 AM, JohnK wrote:

Very very good advice from Nick in these two posts.

Changing like-for-like or interchanging if easy is valid -
modifications aren't. [Unless you deduce something from a *temporary*
mod to allow you to fix the original problem.]
I have had to deal with the fallout from bad approaches: "We"
discovered that, in the Chinese factory, there was an 'engineer'
modifying the units that failed test until they worked or passed.
Things like changing the value of a resistor in a voltage divider that
supplies a ref voltage to a comparator making up for an IC with a
leaky input ( or a solder bridge to a different part of the circuit as
in one of the customer returns that I analysed). Eeek!!

John K


- Original Message - From: "Nick" 
To: "neonixie-l" 
Sent: Thursday, March 09, 2017 1:37 PM
Subject: [neonixie-l] Re: Taylor Edge Nixie Clock Kit



...Also, reading your problem description isolates the issue to the
10s digits.

The 10s are driven by 7490s whereas the units are driven by 7492s. Do
you have the right chips in the right places?

I'd also try swapping round the 74141s between the 10s and units to
see if the problem moves with them - 74141s can fail


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Re: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

[JohnK]

Very very good advice from Nick in these two posts.

Changing like-for-like or interchanging if easy is valid - modifications 
aren't. [Unless you deduce something from a *temporary* mod to allow you to 
fix the original problem.]
I have had to deal with the fallout from bad approaches: "We" discovered 
that, in the Chinese factory, there was an 'engineer' modifying the units 
that failed test until they worked or passed. Things like changing the value 
of a resistor in a voltage divider that supplies a ref voltage to a 
comparator making up for an IC with a leaky input ( or a solder bridge to a 
different part of the circuit as in one of the customer returns that I 
analysed).Eeek!!


John K


- Original Message - 
From: "Nick" 

To: "neonixie-l" 
Sent: Thursday, March 09, 2017 1:37 PM
Subject: [neonixie-l] Re: Taylor Edge Nixie Clock Kit


...Also, reading your problem description isolates the issue to the 10s 
digits.


The 10s are driven by 7490s whereas the units are driven by 7492s. Do you 
have the right chips in the right places?


I'd also try swapping round the 74141s between the 10s and units to see if 
the problem moves with them - 74141s can fail


Isolate the problem.

Nick

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RE: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

[Tidak Ada]

It is also possible one of the 7490 or 4717 chips isn't functioning correct or 
damaged or a bad soldering. Check your soldering work with a magnifier glass

eric

-Oorspronkelijk bericht-
Van: neonixie-l@googlegroups.com [mailto:neonixie-l@googlegroups.com] Namens 
Nick
Verzonden: donderdag 9 maart 2017 4:07
Aan: neonixie-l
Onderwerp: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

...Also, reading your problem description isolates the issue to the 10s digits. 

The 10s are driven by 7490s whereas the units are driven by 7492s. Do you have 
the right chips in the right places?

I'd also try swapping round the 74141s between the 10s and units to see if the 
problem moves with them - 74141s can fail

Isolate the problem.

Nick

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