Re: [neonixie-l] Re: Maybe a stupid question...

[karl welty]

With the parts order having arrived I was able to hook up the circuit
per my idea. It works exactly as I hoped it would. Thousands
(seemingly) of variations based on the settings of the pots. It
outputs a changing voltage right in the range of the intended VCO I
plan to have downstream. Initial testing mostly complete I can now
build up the VCO card and determine the best way to interface them. It
was a long week, this was a nice way to round out the weekend.

https://youtu.be/GGKjt8f74bw

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[neonixie-l] Re: Constant current regulator for Nixies

[gregebert]

Generally, the '1' is actually two parallel wires,so it's comparable in 
length to the other numerals.

Datasheets for segmented displays clearly show different currents for 
various segments, but I have not seen that for full-formed nixies (eg, 10 
cathodes for 0-9)

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[neonixie-l] Re: Constant current regulator for Nixies

['jf...@my-deja.com' via neonixie-l]

On Saturday, August 13, 2016 at 5:45:22 PM UTC-7, ZY wrote:
>
> ...maybe some regulation circuitry would be worth it in the long run?
>
> If you do this, you might want to modulate the current proportional to 
illuminated length of each character, so an 8 would draw more current than 
a 0 and much more than a 1.  If these dimensions are not already in the 
spec sheet, you could measure them yourself.
 

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[neonixie-l] Re: Constant current regulator for Nixies

[gregebert]

For anode-side, I use a PMOS device (see attached picture). The current is 
set to (PRDV-Vgs)/R7.  You can get Vgs(on) from the datasheet, usually it's 
around 4V for higher-voltage PMOS devices. The PDRV signal generated from a 
potentiometer and a small 12V DC-DC converter; adjust it to obtain proper 
current..

The zener diode protects the gate-source from unexpected spikes. The 10meg 
resistor is for bleeding any ESD; the value isn't critical but I use the 
highest value SMT resistor I can get at low-cost. I'm being overly paranoid 
about voltage spikes and ESD because if the PMOS device is damaged it could 
fail later in time and damage the nixie. The resistor R8 is intended to act 
like a fuse, though R7 would likely burn out first. It will take about 20mA 
to do that, which is a lot more than the nixie tube is rated for, but at 
least it wont allow basically unlimited current.



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[neonixie-l] MOD-SIX GPS Repeater

[Jack Buechler]

I have a spare GPS Repeater Version 1 – does any one need one?

Let me know



From:  on behalf of ZY 
Reply-To: "neonixie-l@googlegroups.com" 
Date: Sunday, 21 August 2016 at 11:09
To: neonixie-l 
Subject: [neonixie-l] Re: Constant current regulator for Nixies

What is your method of current regulation? For example, do you use a PnP 
transistor or the lm317 method, or something else? I have room to add something 
for my anodes, but I'm unsure if using a transistor would be accurate.

On Sunday, 14 August 2016 03:02:17 UTC-4, gregebert wrote:
I use current-regulation on my nixie designs, and I've done cathode-side as 
well as anode-side regulation.  Where you decide to regulate the current 
depends upon the driver you select. So far, all of my designs use direct-drive 
(non-multiplexed).

My 'Tomorrowland' clock uses HV5532 drivers (it has fourteen IN-18 tubes), so I 
regulate current on each anode. Yes, there are 14 current regulators My 
wristwatch uses NPN transistors to drive the cathodes, so I regulate the 
current on each segment.

Since 10mA fuses really aren't available, I size the resistor in the 
current-regulator so that it will operate at about 1/2 it's rated power during 
normal operation. For example, an 0805 SMT resistor is rated for 1/8 Watt, so I 
try to design for around 50-60mW. If a gross failure in the regulator occurs, 
the resistor should overheat and open. I have not tested it, though. I have a 
fuse on the power supply, and use the smallest value that will handle max 
operating current.

If you really want to be paranoid, monitor all of your anode currents with a 
multi-channel ADC. I've never done that, but it sounds like a fun project.

For cathode current-regulation, you would use an NPN or NMOS transistor; 
anode-side would use a PNP or PMOS. I found that high-voltage PMOS devices 
aren't nearly as common as NMOS.

If you use MOS devices, I'd recommend a zener-diode across gate-source and also 
very-high resistors (10Meg +) across drain-source to protect from ESD or 
unanticipated voltage spikes. It's probably overkill but SMT devices are so 
cheap and small it's worth the cost to me.
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[neonixie-l] Re: Constant current regulator for Nixies

[ZY]

What is your method of current regulation? For example, do you use a PnP 
transistor or the lm317 method, or something else? I have room to add 
something for my anodes, but I'm unsure if using a transistor would be 
accurate.

On Sunday, 14 August 2016 03:02:17 UTC-4, gregebert wrote:
>
> I use current-regulation on my nixie designs, and I've done cathode-side 
> as well as anode-side regulation.  Where you decide to regulate the current 
> depends upon the driver you select. So far, all of my designs use 
> direct-drive (non-multiplexed).
>
> My 'Tomorrowland' clock uses HV5532 drivers (it has fourteen IN-18 tubes), 
> so I regulate current on each anode. Yes, there are 14 current 
> regulators My wristwatch uses NPN transistors to drive the cathodes, so 
> I regulate the current on each segment.
>
> Since 10mA fuses really aren't available, I size the resistor in the 
> current-regulator so that it will operate at about 1/2 it's rated power 
> during normal operation. For example, an 0805 SMT resistor is rated for 1/8 
> Watt, so I try to design for around 50-60mW. If a gross failure in the 
> regulator occurs, the resistor should overheat and open. I have not tested 
> it, though. I have a fuse on the power supply, and use the smallest value 
> that will handle max operating current.
>
> If you really want to be paranoid, monitor all of your anode currents with 
> a multi-channel ADC. I've never done that, but it sounds like a fun project.
>
> For cathode current-regulation, you would use an NPN or NMOS transistor; 
> anode-side would use a PNP or PMOS. I found that high-voltage PMOS devices 
> aren't nearly as common as NMOS.
>
> If you use MOS devices, I'd recommend a zener-diode across gate-source and 
> also very-high resistors (10Meg +) across drain-source to protect from ESD 
> or unanticipated voltage spikes. It's probably overkill but SMT devices are 
> so cheap and small it's worth the cost to me.
>

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[neonixie-l] Re: Burroughs Panaplex II clock display...

[taylorjpt]

I have a pile (~1K) 11 digit calculator displays and eventually settled on a 
0.5mm thick double sided translator board installed with conductive epoxy.  The 
connection now becomes a simple DIP header: http://www.ebay.com/itm/140729423185

I remember having a bag of the clips back in the '80s and thinking... "When 
would I ever need these?".

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