Figuring out voltages for a VFD

[Boris Gjenero]

I'm using a surplus VFD (vacuum fluorescent display) without any info:
http://www.sciplus.com/singleItem.cfm?terms=2391&cartLogFrom=Search
It's labeled: NEC FIP11AMW8 NO. 2 - 8 JAPAN

It is 16x multiplexed. The glass is about 11x5 cm and it has 12
14-segment characters, two 14 segment bar graphs, two 7-segment
characters and various indicators for use in a stereo system. Almost
everything is in the familiar greenish phosphor and there are a few
reddish indicators.

I'm giving it a 3 V peak-to-peak square wave for the filament,
centered around 3.2 volts and generally 20 V for the anodes and grids
and of course multiplexing. This works pretty well but I'd like to be
more certain about what I should really be giving it.

I'm wondering whether to boost the filament voltage. Now they're
almost unnoticeable in total darkness. If I take out a diode they
become noticeably reddish in total darkness with the display off but
are otherwise not really noticeable. Display brightness increases and
it's a bit more equal. Of course I can increase the anode voltage
but perhaps lower anode voltage means longer life.

I'm also wondering about the anode voltage. With the current filament
voltage brightness changes a lot up to 22 V or so and then not as much
as I increase towards 30V. 20V seems good for the greenish phosphor
but it seems like the red one needs more to light up well.

--
Boris

 

[Wolfgang Mahringer]

Hi Boris,

Generally, the filament should be quite good visible in total darkness.

The anode voltage is normally uncritical, as long as your anode drivers
are capable of that voltage.
I have a similar display where the anode voltage can be as high as 70V
(datasheet). I use 55V, since the drivers have a maximum of 60V.
Another green display I just look at has an anode voltage of 32V and a
filament voltage of 3.7V AC, with a mux ratio of 1/13.75.

HTH
Wolf



--
From-address is Spam trap
Use: wolfgang (dot) mahringer (at) sbg (dot) at

 

[Boris Gjenero]

On Sun, 23 May 2004 22:02:59 +0200, Wolfgang Mahringer
<yeti201@gmx.at> wrote:

Hi Boris,

Generally, the filament should be quite good visible in total darkness.

Ok, I'll boost the filament voltage. The display definitely looks
better then.

The anode voltage is normally uncritical, as long as your anode drivers
are capable of that voltage.
I have a similar display where the anode voltage can be as high as 70V
(datasheet). I use 55V, since the drivers have a maximum of 60V.
Another green display I just look at has an anode voltage of 32V and a
filament voltage of 3.7V AC, with a mux ratio of 1/13.75.

I thought the anode voltage was critical, that if it was too high,
display life would be seriously shortened.

BTW The drivers I'm using can do 60V as well.

Thanks for the response.

--
Boris