Wiring up a VFD tube????? (IVL2-7/5) - Page 1
Forum section: electronics / projects

author: shanecy
author_rank: Contributor
timestamp: January 07, 2015, 12:02:02 am
content: I've worked all day long on this VFD tube and cannot get it to light up. The three filament wires glow red so I know their working but as far as getting the display segments to light up I cannot achieve. I have not been able to find the datasheet for this display. The manufacture I ordered it from (Russia) did not have the datasheet. I've searched everywhere even Ebay. I did find the datasheet on Ebay but it was in Russian. I was able to get the basic Filament and Grid Voltage specs from other projects I've researched online but as far as wiring it up and understanding the pinouts i've had no luck. I've examined the individual pinouts and drew out a sketch showing where they are connected (see attachment) but other than that I know very little on what to do next.First time I hooked up the display as shown in the attachment of my sketch. 2V to the filaments and 14V to the grid. I then took a wire which was connected to the 2V rail and touched a segment to see if anything happened. Nothing did. The filaments were glowing though.The second time I implemented a resistor between the 14V rail and +pinout of the Grid. In the first try i noticed it was drawing excessive current (1A) so I implemented a current limiting resistor. Other than that I kept everything the same. I tried touching one of the segments again and nothing.I'm out of options on knowing what I should do next and was hoping someone could help me out on here. I honestly just want to test out the display but just to make it clear I will be driving the VFD with a MAX6920. The datasheet is located here (http://www.maximintegrated.com/en/products/power/display-power-control/MAX6920.html). Maybe I need to implement this driver chip to test it out?! Maybe not?! I'm hoping someone can get me back on track. Interfacing the MAX6920 is a completely different topic so I won't go into asking help with that yet. I've read some short app notes but without any datasheet to the VFD its been hard for me in figuring out anything period.Also here is the link to the Russian Datasheet if anyone's curious (http://www.ebay.com/itm/Lot-of-2-IVL2-7-5-IVL-VFD-DIGIT-CLOCK-DISPLAY-TUBE-GREEN-Tube-New-FREE-SHIPPING-/250909836673).This is probably to much but i'll include a rough rough design sketch of how I though I might wire up the MAX6920 to the VFD. As I mentioned though I really need some technical docs or advice cause i'm just guessing on my design so far.

author: helius
author_rank: Super Contributor
timestamp: January 07, 2015, 12:41:39 am
content: In your schematic you have drawn +14V on pin 22, and ground on pin 2, is that right?Have you tried using a higher anode voltage, such as using the same +14V grid supply for anodes?

author: shanecy
author_rank: Contributor
timestamp: January 07, 2015, 12:59:28 am
content: Correct...I grounded pin 2 and supplied +14V on pin 22. I have not tried using a higher anode voltage. I will give this a try ASAP tomorrow and post an update. As for the other wiring in general am I correct?

author: Andy Watson
author_rank: Super Contributor
timestamp: January 07, 2015, 01:08:24 am
content: Quote from: shanecy on January 07, 2015, 12:59:28 amIf I have interpreted your diagram correctly, pins 2 and 22 are connected to the same point - i.e. the grid. To light-up a segment, you will need to put the most positive voltage on an Anode(s), probably via a current-limiting resistor (few K ohm should work). The filament is also the cathode - so this must be connected to the most negative voltage (ground in this case). The grid may need to be biased positive (I'm not familiar with this tube), but it should not require much current, nor voltage to make the segments light-up.

author: shanecy
author_rank: Contributor
timestamp: January 07, 2015, 01:15:56 am
content: Why does recent documentation mention "Rated(Nominal) Voltage of Filament 2 - 2.65V? Not arguing just curious why this is. Also when you say Biased Voltage what would be a good starting point?So from what i've gathered I should try the following tomorrow...1.) Connect Filaments to ground2.) Connect Grid to a biased positive3.) Turn up the Voltage on the Anodes.

author: Richard Crowley
author_rank: Super Contributor
timestamp: January 07, 2015, 01:37:54 am
content: 14V just doesn't seem like enough to get them to glow, assuming everything else is OK.Are you sure you have the polarity right? Won't hurt anything to try it the other way.IIRC, the filaments should NOT be VISIBLY glowing. If they are, then you are probably driving them too hard and will seriously reduce their life expectancy.Sounds like too much current through the filament (which will only limit their life). And not enough voltage on the anodes to get them to glow.

author: helius
author_rank: Super Contributor
timestamp: January 07, 2015, 01:41:15 am
content: Yes, the filament should not visibly glow (although it is hot and emitting infrared).In VFD circuits, the filament is usually driven by an AC voltage superimposed on a DC bias to improve drive uniformity between the left and right sides. But this is not necessary to test that the VFD works.

author: Andy Watson
author_rank: Super Contributor
timestamp: January 07, 2015, 01:46:54 am
content: Quote from: shanecy on January 07, 2015, 01:15:56 amOne side only, you still need the 2-2.65V across the filament. Ideally you would drive the filament with AC, but for the sake of getting it to light up it will be easiest to start with one side grounded.QuoteYes. This websitehttp://www.noritake-elec.com/vfd_operation.htmlappears to suggest that the grid may need to be at the same potential as the anode. You may have to experiment.QuoteYes, the anodes must be the most positive. I'm not sure if the resistor is required - but it won't hurt for testing purposes.

author: shanecy
author_rank: Contributor
timestamp: January 08, 2015, 01:26:38 am
content: In case someone has the same question i'm including my results from the advice I received from this discussion.Please see the attached files for a more detailed description of my testing. I also included a picture of the wiring.Summary:*I only powered up the far left digit "grid" with all 7 anodes lighted.*The grid needed a resistor on the low side. Otherwise when I pulled the grid to ground the anodes would shutoff.*The anodes needed more voltage as everyone expected. The anodes were very dim though. When I increased the filament voltage the anodes would become brighter but by doing so the filaments would start to glow bright orange starting around 3.5V and up. Also when I pulled an anode to ground the anode would shutoff as I expected.The specs for my two power supplies I used are as follows:Model ---> Agilent E3631AVoltage Source 1 was set at +14V indicating 14mAVoltage Source 2 was set at +2.5V indicating 64mAMy voltages for each component of the VFD are as follows:Filaments ---> +2.5VGirds ---> +14V (Measured current draw was 14.32mA with a 1K resistor)Anodes ---> +14V (Measured current draw on one segment was ~14uA and the rest were ~8uA)

author: Richard Crowley
author_rank: Super Contributor
timestamp: January 08, 2015, 01:40:21 am
content: This appears to be a compreshensive and practical review of how VFDs work and how to use them....http://www.noritake-elec.com/vfd_operation.html

author: shanecy
author_rank: Contributor
timestamp: January 09, 2015, 12:36:34 am
content: I've been experimenting with how I power the filaments in my VFD. According to this articlehttp://www.noritake-elec.com/vfd_operation.htmlunder the section VFD drive characteristics there are three possible ways to drive the filaments.1.) Using a transformer2.) Using a DC to AC converter3.) Using my previous setup where I just create a biased positive across the filamentsI cannot use option (1) because I'm putting everything on a PCB that needs to be as small as possible since the end product is a watch.I would like to use option (2) because this will, to an extent, provide even potential across the filaments versus option (3) where one side of the filaments will have a potential closer to 0V making the display dimmer on one end. I found a DC to AC converter called a LM9022http://www.ti.com/lit/ds/symlink/lm9022.pdf. The problem is i'm having a hard time finding them since their obsolete. Any ideas on where I could find this chip or alternatives that may provide the same function for powering the filaments.

author: w9gb
author_rank: Contributor
timestamp: March 24, 2023, 11:04:07 pm
content: There are NUMEROUS CLOCK Projects using VFD … Use Google(Do you Know How to Search?)I found several, with DIY Build parts lists and schematics.Heathkit GC-1107 Clock used VFD … here is schematic.https://www.nostalgickitscentral.com/heath/schematics/heathkit_schema_gc1107.pdfHeath GC-1107 MANUALhttp://tubularelectronics.com/Heath_Manual_Collection/Heath_Manuals_G/gc-1107/gc1107_man.pdfHeath used Mostek Clock ICs in 1970s and early 1980s.http://www.decodesystems.com/vfdclock.htmlDIY Build using MM5316N clock chiphttps://en.kohacraft.com/archives/making-a-clock-using-vfd-display-tube-iv-6-and-mm5316n.html

author: wasedadoc
author_rank: Super Contributor
timestamp: March 25, 2023, 12:07:38 am
content: @w9gbDo you realise that the last time the OP logged in to these forums was 8 years ago?

author: shakalnokturn
author_rank: Super Contributor
timestamp: March 27, 2023, 01:10:18 am
content: If he's anything faster than I am the project is finished