Thanks for the schematic. It would be overkill if it was just for a clock but I 
want to save cycles on the MCU since it was multiplexing the tubes and boosting 
the voltage. I was taking cycles away from the MCU and it was causing 
flickering. I looked at either a PT6311 or having a dedicated attiny to run the 
multiplex/booting and feeding via serial the tube display.

So it just looks like the filament voltage is biased (is that the current 
term?) to the grid voltage. So -18v filament one end and -20 the other end and 
grid/anode is -20v. I am using MC34063 inverted to generate the voltage. I'll 
give it a shot it and see what happens!


________________________________
 From: Bill van Dijk <[email protected]>
To: [email protected] 
Sent: Sunday, July 21, 2013 7:07 AM
Subject: RE: [neonixie-l] IV-11 VFD
 


Spencer,
 
Attached is the schematic for my IV17 clock with a PT6311. It is a chip that 
takes a bit of figuring out, also on the software side. My clock displays time 
(why not eh?) and the full date in a marquee format as well as ambient 
temperature. I would suggest the PT6311 is possibly a bit of overkill for a 7 
segment based clock design.
 
Bill v. Dijk
 
From:[email protected] [mailto:[email protected]] On Behalf 
Of Spencer
Sent: Saturday, July 20, 2013 2:29 PM
To: [email protected]
Subject: Re: [neonixie-l] IV-11 VFD
 
Got it working! It lights up now and it looks like I will have to change the 
filament resistor. I was using a 30 ohm with +5V but ooo boy does it get bright 
with that. I'll drop it down to around +1.5V and can take it from here.
 
Thanks again.
 

________________________________

From:John Rehwinkel <[email protected]>
To: [email protected] 
Sent: Saturday, July 20, 2013 12:54 PM
Subject: Re: [neonixie-l] IV-11 VFD

> Thanks for the reply. I put the -25v on pins 1 and 11 (cathodes) and GND on 
> pin 2(grid) and GND on a random anode to see if it would light up and nothing 
> illuminated.

The filament needs to be hot to emit electrons for the VFD to operate - this is 
normally accomplished by heating it electrically.  I did kind of gloss over 
this -- you have to have voltage across the filament as well - this is true no 
matter how the other voltages are supplied.  The "ideal" method is to have a 
small center-tapped transformer providing the AC filament voltage (generally 
something between half a volt to a few volts), and hook the -25V to the center 
tap.  I often use a generic 6.3V filament transformer, with series resistors to 
drop the voltage to whatever the VFD filament needs.  Some people don't want to 
bother with an AC filament voltage, and just run it with DC - this will work, 
but can lead to brightness gradients in some tubes.

So, just to light something, at a minimum, you'll need -25 volts at one end of 
the filament, -(25 + filament voltage) at the other end of the filament, and 0V 
at the grid(s) and anode(s) you want to light.

- John

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