Getting started with an 11 Digit VFD - Page 1
Forum section: electronics / beginners

author: Mooncabbage
author_rank: Newbie
timestamp: July 07, 2015, 11:58:50 am
content: First of all, hi everyone, this is my first post on the forum, so if I inadvertently put my foot in it, I pre-emptively apologise. Now down to brass tacks.I am fairly new to hobby electronics, having done some in high school physics, and played with Arduinos at uni, and have just started digging deeper. I'm finding it quite difficult to get used to all the lingo and ideas, particularly practical applications and uses for things. I figure the best way to learn is by doing though, and with that in mind, I've run into a bit of a roadblock.My current project is to make little modular bits for a Kerbal Space Program type simpit/controller, and for a few dollars I couldn't turn down Jaycar's cheapo 11 digit VFDs. They seemed like the perfect choice for the retro design aesthetic I'm shooting for. Trouble is, they're a discrete part with no driver board, and incredibly poor documentation. That said, I could probably still get it going, except it seems the filament needs an AC current, and I wouldn't have the foggiest as how to provide it with one. Thus my question is twofold:1) How do I get the AC power to drive this thing for breadboard testing? I don't have a bench supply readily available, or any such fancy doodas. Is there a magic trick with discrete parts I can try? 555 Timer chip and a couple of discrete transistors maybe? This can't be the first time anyone has ever run up against this problem, but I don't have the vocabulary to find the solution on my own.2) How would you approach providing this AC power to the module? I don't know what best practice for this sort of thing is, but I was planning on wiring up a little board that could be told "Display 3798098.45" by a microcontroller, and would just do it. Any ideas would be greatly appreciated.Finally, if it's in any way relevant, it's a Futaba 11-ST-26ZA,Jaycar Part No. ZD1880.

author: SuzyC
author_rank: Frequent Contributor
timestamp: July 07, 2015, 01:31:34 pm
content: The filament will work with AC or DC. RTFM.Make one or two power supplies if you don't have even one. Just find some wall-wart or brick power supply discarded for a laptop and add a lm317 adj. reg. chip to adj. voltage and you have a power supply..or use batteries.http://www.noritake-itron.com/subpages/applicnotese/vfdoperapn.htm

author: Mooncabbage
author_rank: Newbie
timestamp: July 07, 2015, 01:54:09 pm
content: I have read that you shouldn't run the filaments on DC, because it causes uneven brightness on the display. Also the manual says to run it on AC.... cause you know, I read it.

author: bktemp
author_rank: Super Contributor
timestamp: July 07, 2015, 02:03:40 pm
content: DC works, it won't damage the VFD or do anything bad except the uneven brightness. For the first test a simple resistor to get the correct voltage is probably the best and easiest solution, because you can reuse the existing 5V logic supply voltage.Better solutions are 5.2 AC Filament Drive (50 or 60Hz) and 5.3 Pulse Filament Drive (High Frequency RMS) in the link above. Both are a bit more complicated and need more parts.The datasheet is crap and seems wrong. 12V sounds very low for a 1/15mux display. It will work on 12V, but only very dim. If you need a higher brightness 20-30V is commonly used for such displays.

author: SuzyC
author_rank: Frequent Contributor
timestamp: July 07, 2015, 02:56:52 pm
content: If you can find any discarded older cellphone charger or other wall warts, take them apart, if they are "heavy" they will probably have a transformer that can supply a voltage just a little higher than is required.These transformers have a low-voltage secondary output winding, find the transformer secondary output wires and bring these out to a resistor, these wires are easy to spot, they are going to the bridge or diode rectifiers, the High Voltage dangerous connections connect directly to the power plug and usually are well insulated. Once you attach wires to the secondary winding on the transformer, just one resistor and ohm's law to get the AC power for the VFD filament.Add one more DC output wall-wart and you'll have the DC to drive/bias the rest of a VFD display circuit.

author: Mooncabbage
author_rank: Newbie
timestamp: July 07, 2015, 03:33:23 pm
content: Thanks for the help guys!The jaycar website datasheet is absolute rubbish, the one I got when I bought the displays is a little better, and from what I can work out, requires running the Back Planes on 4V AC, or rather 3-5V AC. Or something. I can put the data from that sheet up on here, would it be better to scan the doc, or just type out the specs?I have an entire box of old wall warts, chargers and the like, in my basement.

author: BrizeeBlewitup
author_rank: Newbie
timestamp: August 17, 2015, 07:03:07 am
content: Hi all. I brought one of those Jaycar displays a few weeks ago. I am using an Arduino to operate it. I have 3 signal diodes in series with the filament wires to reduce the Arduino 5v rail voltage to about 3vDC. This works great without having the wires visibly glowing. I am using the UDN6118A Fluorescent Display Driver ICs, also available from Jaycar, to convert the logic level 5v of the Arduino to the high anode voltage necessary to run the display. Simply feed the 8 outputs of each of your shift registers into the driver IC, and connect the drivers outputs to the display's grid and segment pins. I am feeding a seperate anode voltage into the driver IC's, this is about 22V DC for optimum brightness, and 12V for a dim (night-time) display. Running the filaments on DC doesnt seem to produce any noticable un-evenness of the display brightness with the anode voltage at 22V, but can be seen slightly when it's reduced to12V.

author: JoeN
author_rank: Frequent Contributor
timestamp: August 17, 2015, 07:49:24 am
content: If I can do it I bet you can. uC: ATMEGA328P-PU, HV driver: PT6306, Filament Driver: LM9022 (obsolete but available on eBay)

author: BrizeeBlewitup
author_rank: Newbie
timestamp: May 27, 2018, 11:30:52 pm
content: I used one of these Jaycar 11 digit VFD's. Here's what I did: I used 3 volts DC on the fillament wires. I only used 8 digits, the 8 most significant. Put the negative end of the fillament connection near the least significant end, this avoids one end appearing brighter. I used 18 volts on the grids and the anodes, via a dc boost converter. You will need the driver chips, you can probably use something like the Max6931. This multiplexes the display and provides filliament output supply, however I used the UDN6118 IC's. These have 8 inputs and outputs, the chips are powered with the 18 volt supply the anodes need, then they convert 5v logic to the 18v needed to drive the anodes/grids. You need 2 of these, one for the 8 grids, and one for the 7 segments and the decimal. I then drove the 16 inputs with 2 595 shift registers, running similiar code as that used to multiplex an LED display. Be sure to common-ground the 18 volt supply with the microcontroller's ground.

author: james_s
author_rank: Super Contributor
timestamp: May 28, 2018, 10:37:16 pm
content: For the filament DC is fine for testing, then if you find it provides uneven brightness you have lots of different options. One is to use a mains transformer that puts out a suitable AC voltage, a resistor can be used to drop the voltage if needed. Another is to build a small DC-AC converter, a Royer oscillator is very simple and will usually work even with random junkbox components. You could make an H-bridge and drive it with a 555 or other oscillator, or pins from your microcontroller. You could look around for an IC specifically intended to drive VFD filaments.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: May 29, 2018, 01:50:30 am
content: Take a look at how Dave does something similar for a LCD.https://youtu.be/pW4HjuH1QRY