| | I can't get them to run correctly. | | | | Anyone else had any experience? | | Yup. I don't know why they were intentionally built that way, but | there is no control over the individual elements. The best you can do | is get one whole column to light up.
Am I like stupid here !? I looked at the pinout from the eBay listing, and assuming its correct, you should really have no problem running this thing. The grids select the rows (1-9), and the anodes (aka elements, & segments) control the column (1-7). Put +20V on a grid, and +40V on an anode, and a specific dot should light up. Of course 4.5V+/-0.5V should be across the filament pins, with the negative side of those 20V & 40V sources tied to one or other of the filament pins (cathode). To make any kind of bit-map pattern on this device requires that you MUX the individual device. Either scan thru the rows or columns sequentially, and put the corresponding bit patterns on the columns & rows, in turn. This all assumes that the data given in that eBay listing is correct. This device is clearly for people who know both how to fire up VFDs, and play with uCs. A VFD is a directly heated vacuum tube. That's right, vacuum. No gas. The filament needs a low voltage at some relatively high current to heat it into thermionic emission just like a regular vacuum tube. Usually just enough current is applied so the filaments are just under visibly glowing. The filament is also the cathode. That's the directly heated part. The anodes are coated with the phosphor, intended to light up when electrons hit it. To get the electrons to flow from the cathode to anode(s), both the grid(s) and anode(s) must have a positive voltage on them. The grid is the only thing that's a little different. In most vacuum tubes, there is conduction, when the grid is at zero, relative to the cathode. On a VFD, there must be some positive voltage. Its really a bias issue, since in both cases, conduction occurs in the more positive position. Vacuum tube: (-V=off, 0V=on); VFD (0V=off, +V=on). Think depletion mode (vacuum tube) versus enhancement mode (VFD) N- channel FETs. Also in most power tubes, they show characteristics, from very negative to very positive voltages applied to the grid. Finally, get it out of your head, about thinking about a VFD, the same way you think of a nixie or LED. Nixies and LEDs are lit by stick opposite voltages across the devices. In VFDs the cathode is always at a fixed point, and the both grids & anodes (segments) must be brought positive. Yes, the filament can be AC or DC, but its average DC bias level must be fixed. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
