On 12 Mar 2012, at 16:47, Sven Killig wrote: > Hello Group! > > I received > http://de.mouser.com/ProductDetail/Vishay-Dale/PD007D07001S51/?qs=sGAEpiMZZMvkC18yXH9iIurp2WUOVpc7D8%2fd1LKTOnY%3d > some days ago, wondering how to drive it. Thankfully I discovered > http://www.tubeclockdb.com/forum/Builders-Forum/86-Cherry-alphanumeric-display.html > which drives a compatible display. The annotated PCB: > http://www.tubeclockdb.com/Alphanumeric_clock1.pdf > Now I'm in the process of doing the PCB layout and getting my BOM together. > Since I'm more into software normally, I have some questions: > 1. How do I get the values of the resistors in the upper part of the PCB > (e.g. R214, R198 and the one between them)? What power should they be rated > for? The circuits seem to resemble drivers like the one in > http://www.clock-it.net/neon/bally/6-Digit_Display_Driver_(AS-2518-21).pdf > with currents from > http://www.babcockinc.com/babcock/documents/doc_471.html > 2. Isn't it neccessary to drive the "SCANNING KEEP ALIVES 1-16" pin (#1)? > 3. It seems I only can get either 100 V or 120 V Zeners. What would you > recommend? > > Thanks a lot in advance!
Hi Sven. You seem to have linked to various documents to do with various clocks of mine, so I better respond. The circuit I came up with is a hybrid of the typical circuit diagram used to drive a 6 or 7 digit seven segment display and the circuit used to drive the 16 digit alphanumeric displays in pinball displays. Those displays as used in pinball machines had a system involving -100v 0v and 90v. There were obsolete UDN chips running the high and low side. In practice a lot of these display boards failed with the chips working close to their maximum and people have resorted to workarounds to replace them. I looked at the design for my BK2K, Black Knight 2000. 1] You get the values for those resistors by looking at the circuit diagram and parts list for any pinball machine that uses them. It's just one resistor change to adjust the brightness balance for the segments. Otherwise I used the high and low side drivers as in the 6 and 7 digit Bally machines. As you say, there's a PDF of these diagrams on my Clock-It website at: http://www.clock-it.net/neon/bally/6-Digit_Display_Driver_(AS-2518-21).pdf and http://www.clock-it.net/neon/bally/7-Digit_Display_Driver_(AS-2518-58).pdf I used 1/2w resistors. No I didn't get the values from Babcock, nor do I see any values on the Babcock document you linked to. I got them from my BK2K pinball schematic and parts list - only the parts list has the values, so you have to find each segment on the schematic and match up the resistors. I'd have to look to see what values I used, I probably wrote them down somewhere. The 100k resistors on the digit drivers should be 1/2w too, although pinball manuals say 1/4w. They cook and burn out. 2] I don't use pin 1. My display works just fine, no it is not necessary and I don't think pinball machines use that pin either, from what I can see. Pin 90 does not exist on my Cherry displays, so N/C it certainly is. 3] The 100v zener will be fine. It's simply a pull mid. The techies here will tell you what that is all about. I'm not sure, I think it's about fast firing or reducing ghosting or something. I used a 110v zeners because I pulled one from a stack of dud display boards I had handy. You need to sweep the display quite fast to get it flicker and ripple free, you are doing a 16 multiplex. I used a PIC microcontroller to do this with a counter outputting a 4 bit code to a 1 of 16 decoder with latch and inhibit. You could simply make a four bit counter and have it free-running the 1 of 16 decoder to sweep the display. You could still use the inhibit pin to blank the display when necessary. This would take the load off the microcontroller and free it up to do other things which you then don't have to interleave with the display routine. I will probably do this in future as it can be tricky with various scrolling routines taking different times and as a result varying the brightness - characters start to jump out at different brightnesses. When adjusting the high voltage it will tell you when the voltage is correct. Too high and you will see some arcing and ghosting on unlit segments. Too little and you get flickering and uneven illumination. There is a sweet spot, you will know it. My routine seems to work well for a rock-steady display using a PIC. I added a bcd to 7 segment chip in case I want to simply send numbers rather than segment patterns individually, but in the end never used it. I defined all the character shapes in a word array corresponding to the ascii code for that character - send the ascii number for that character and it switches those segments on. John S -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
