On Jan 30, 4:49 am, David Forbes <[email protected]> wrote: > On 1/30/12 12:06 AM, Cobra007 wrote: > <snip> > One thing about Nixie tubes that you may not be aware of is that they > need some time to start firing, because the plasma is triggered by an > external source of energy such as a photon from the room lighting or a > stray cosmic ray. The less ambient light there is, the more time they > need to start. If you reduce the duty cycle in the dark, you may find > that the display doesn't start reliably. </snip>
<snip> > This is why some Nixie tubes were made with radioactive krypton in the > tube. But not the 5870 series, as they were designed to be used in an > office environment. </snip> Somewhere buried in the archives (or a reference to an article, that was specific to trigger tubes) is a nice calculation that shows that by this time, all of the Kr85 has decayed so no kick-start help either for those radioactively doped ones. <snip> > It may be possible to solve this problem by detecting when the current > starts to flow in the tube, and leave the tube powered up until the > current starts, then begin the PWM operation. > -- > David Forbes, Tucson AZ Hi David... IMO, as the start of the digit ionization is what is unreliable we would have a train of pulses of known duration but with random separation (period, frequency, etc.). You know well that a PWM light intensity modulation is based on turning on and off a digit, so once the digit is turned off for the next cycle we will have to wait again for a random time. This is unless I got all wrong and only the first start of the discharge is the unreliable one. One alternative, discussed before IIRC is to use the decimal point as a bias cathode... if fully lit of course it will upset all digit voltages, but perhaps it could be used only as bias at low current as some of the trigger tubes did... Gaston -- 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.
