I managed to remove this from an old till my friend's mother was throwing out. Does anyone know how to drive it and how to connect it up? Sputnik
it is a VFD, vacuum flurescent display. connect 3v across the two end pins, the little filaments going horizontally should glow. Then connect some volage (not sure how much, usually around 3-5v) across the pins for the segements, should be 7 segment pins and 9 digit pins (+ more for decimal points, 1/2 indicator etc..) It has to be driven in multiplex.
this site explains how vfd's work pretty well: http://hem.passagen.se/communication/vfd.html and you don't want to be able to see the filament glowing, it doesn't take much voltage to do the trick. Basically, you want to put one end of the filament at 0v, the other at 2-3v, and to get a segment to light up you put one grid and one segment wire at 9+ volts. So if you have 2 AAs and a 9 volt, connect the AAs across the filament, and the 9 volt from the positive filament side to whatever grid/segment wires you want. (this puts the segments at +12v and is a little brighter than tying the grounds together.) And for testing, you can just short all the non filament wires together and when you put the +12v on the entire display lights up Now for my question, I've got one working, but im having trouble figuring out how to get it controlled by a pic without using lots of transistors, or buying more stuff from digikey. I've figured out that i can put a PNP with it's emitter at 20v, it's collector tied to the controlling pin, and a resistor in series with the base, and that takes an open/collector type input. I can then use a NPN to convert the TTL signal to the O/C signal, but thats two transistors, and two resistors per line, does anybody have a better idea? I don't have anything to power the pic at 20 & ~17v.
Maby a ULN2003 type IC (basically 7 or 8 transitors in a box) not sure what the voltage range on them is but i frequently see them being used for this kind of lark..
Although not an impressive test, I now know that I can get it to work. I didn't want to damage it as well. Thanks guys, Sputnik
