David is absolutely correct about this. Due to each cathode having a slightly different surface area, the currents do vary.
One experiment I have done many times is to get the tube working with about a 15k resistor, and a power supply of about 170 to 175 V DC. Then, while monitoring the voltage drop across the resistor, turn on each cathode and make a table of the observed voltage drops. >From those values, then a 2nd column can be added to the table, and the calculated current entered for each voltage drop. That way you can see the entire range easily and decide if it all falls close enough to where you want it to be. At one time I tended to run the tubes with slightly lower current than the data sheet shows. But, since I learned about cathode poisoning, I now tend to use what the tube data sheet says. The guys who worked at those tube factories knew what they were doing. Chuck ---- Original Message ---- From: dfor...@dakotacom.net To: neonixie-l@googlegroups.com Subject: Re: [neonixie-l] Re: Large nixie display, current discrepancies Date: Wed, 09 Mar 2011 09:17:48 -0700 >On 3/9/11 8:47 AM, Jarek wrote: >> I purposely bought 1% .5W resistors, and did all the testing with >the >> '8' digit. I'll test the current and voltage drop going through >each >> tube. What value should I shoot for for the current and voltage >drop? >> 2.0? 2.25? I've also heard that you should stick to optimal as >close >> as you can... >> > >There's precision, and then there's precision. Nixie tubes are in the >5% >category, not the 1% category. > >Since a Nixie tube is a voltage regulator, it will have a terminal >voltage that's relatively contant with changing current. This means >that >each cathode of each tube will run at a slightly different current >due >to each cathode's slightly different sustaining voltage. > >The upshot is that you can't optimize it to 1%, no matter how hard >you >try. "Close enough" will have to do. > >If it were my gizmo, I would have chosen the nearest "standard" >resistor >value of 15K and been done with it. > >-- >David Forbes, Tucson AZ >http://www.cathodecorner.com/ > >-- >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. > $4.95/mo. National Dialup, Anti-Spam, Anti-Virus, 5mb personal web space. 5x faster dialup for only $9.95/mo. No contracts, No fees, No Kidding! See http://www.All2Easy.net for more details! -- 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.
