How DO VFD Displays Work

[dredwinphd1]

I recently purchased several IV-11 VFD display tubes from Ebay. I would like to  use them to build a 6 digit clock. However, I am unable to find an english datasheet (from Russian). I also grew up in the semiconductor era and not the tube era. What I have been able to glean from the internet is what was posted here a couple of years ago. All I am sure of is that the filament is about 1.2 VDC (typically) @50 mA. The grid voltage is in the 20-25 VDC range and it is usually grounded to the negative side of the filament. The Anode voltage is usually in the same voltage range as the Grid Voltage. I was hoping to use CMOS 4017's to drive these displays at about 12 VDC or so.

Can anyone please educate me on the working of VFD displays, where I might find an English Version of the IV-11 VFD tubes and whether I could indeed use CD40xxB logic with these displays?

Thanks in advance......

[dannyf]

would googling help?

[Richard Crowley]

Google found several examples of clocks using IV-11.
20-25V may be at the lower end of what will light it up.
You will need a higher-voltage solution for controlling it. CMOS 40xx isn't really up to it.

[tiltit]

To drive a VFD you need to supply a relatively low voltage (like 2V) to the filament. Be careful, you can easily blow the filament if you apply to much voltage. Happened to me once. Makes a pretty "Ting" sound.
Then you will need a moderately high voltage supply (about 30V to 60V for old VFDs). For example you could use a MC34063 for that.
A nice chip to drive VFD displays from a microcontroller is the HV5812 shift register. It exists in DIP I believe.

[dredwinphd1]

I did some more googling and found a simple test circuit and was able to get one of my IV-11 tubes to display quite nicely with about 21 volts applied to the anodes and grid. Is it possible to drive the anodes with a interface chip based upon my LSTTL digital clock logic? I did find a driver which would allow interfacing my clock logic. However it is long gone obsolete;-(  anyone have any idea how I might be able to use my LSTTL clock logic (Yes, I could use a uC but want a retro clock)? Suggestions would be appreciated.

[richard.cs]

Most of them seem to want the grid a few volts +ve for on and a few volts negative for off. If you float the cathode to around +6V then you can drive the grids from CMOS logic and 0/12V is -6/+6V relative to the cathode. It's also normal to drive the cathode with a.c., with d.c. you can get a brightness gradient across the display due to the varying cathode-grid voltage along its length. You'd normally need more than 21V on the anode, the low anode voltage might be why you've had to pull the grids so +ve. Are you drawing grid current (bad)? What's your anode current?

They are all a little different though so a manufacturer's datasheet would still be nice to have.

[dredwinphd1]

I finally found a russian and english translation of the datasheet for these tubes. Does anyone have any idea how to make a simple driver circuit so I can drive these tubes with standard LSTTL logic like the 74LS47 or 74LS247. As I understand the datasheet these are open collector outputs? Could I use these outputs to possibly drive a transistor with a collector / emitter voltage of about 60 volts? I have no idea how to come up with this level shifter / driver circuit? Can anyone provide me with a schematic using the LS247 driving a transistor to handle the voltage of the anodes and grid. I suppose it would take 7 of these drivers for each tube for seven segments (a - g). Any assistance would be greatly appreciated. A picture of the circuit, a single stage, would be appreciated since I am not an EE. I spent my professional career as a Quality Assurance Engineer.

BTW, the pinouts on the russian datasheet are not correct. I was able to statically get a single tube up and running but when I checked each anode they did not correspond to the pin out on the data sheet.

For anyone interested in the tube pin outs they are as follows: Pin 1 and 11 are the filament, Pin 2 is the Grid, Pin 6 is segment "a", Pin 5 is segment "b", Pin 3 is segment "c", Pin 10 is segment "d", Pin 9 is segment "e", Pin 8 is segment "f", Pin 7 is segment "g", Pin 4 is the DP.

[miguelvp]

If you share the datasheets it might help others to figure out what is needed.

[dredwinphd1]

Here is the translated data sheet of the IV-11 VFD display tube.