| Electronics > Beginners |
| Getting started with an 11 Digit VFD |
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| Mooncabbage:
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. |
| SuzyC:
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 |
| Mooncabbage:
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. |
| bktemp:
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. |
| SuzyC:
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. |
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