Per,
Hi. I built many copies of several types of Nixie clocks about 10-12
years ago, using multiplexing. They worked very well, with no ghosting
at all.
Things to look for:
1. Ensure that you have a "dead time" after the anode is turned off,
with the same cathode selected, for about a millisecond. The reason is
that if you immediately change the cathode after turning off the anode,
the residual charge on the anode will cause the newly selected cathode
to light in the tube that was just turned on.
2. Any cables connecting the tubes to the drivers will extend this
storage time due to cross-coupling between the wires, so experiment with
longer "off" time with the previous cathode still selected.
On 6/6/15 5:47 PM, Per Jensen wrote:
Hi.
Being a Nixie-hoarder for many years, i’m actually guilty of not having a
working clock at home. The only clock i have working is sitting in the local
hackerspace. It’s an direct driven design and have been working perfectly for
about 6 years now.
As i have a million “real” projects that i am working on, ii’m pretty sure that
getting the time to design a clock “properly” isn’t just around the corner.
On one of those late-night shopping-sprees i came across this board:
http://switchmodedesign.com/collections/arduino-shields/products/open-source-nixie-tube-shield-cut-jump-pcb
<http://switchmodedesign.com/collections/arduino-shields/products/open-source-nixie-tube-shield-cut-jump-pcb>
and ordered 2 pcs.
I “trusted” the website-name (switchmode designs) as the board being designed
by one that knew what he was doing, so i didn’t check schematic or board layout
before i had the boards in hand …. Maybe i should have done that, because that
switcher is the worst design i have /EVER/ seen.
Anyway, apart from that, it works ok-ish.
I wanted to use this board as a “backend” for my own board with tubes. I quickly
whipped up a board for 4 IN-4’s:
https://www.dropbox.com/s/dsk1hv2xly7e9v2/Nixie.png?dl=0
<https://www.dropbox.com/s/dsk1hv2xly7e9v2/Nixie.png?dl=0>
https://www.dropbox.com/s/yn42qtdki3vr7bo/Nixie2.jpeg?dl=0
<https://www.dropbox.com/s/yn42qtdki3vr7bo/Nixie2.jpeg?dl=0>
It’s a milled PCB so that’s why the copper is left around the tracks.
Now i am having this stupid problem - ghosting!
No, it’s not software ghosting, because if i only connect a single tube with
two wires (the wide cable isn’t connected) , sometimes the neighboring tube
lights up, too.
So somehow the tubes being connected only by the cathodes and the anodes
floating, powering one can excite the others.
I even removed the pins for the tubes so the anode pins of the unused tubes is
not even touching the fibreglass-material. Only cathodes is thouching.
(anode-pin connected by flying wire to anode resistor and driver)
https://www.dropbox.com/s/y0xhc9gazrxa120/nixie3.jpeg?dl=0
Is there anything to do here, or should i scrap the boards and design my own
direct-driven circuit?
// Per.
--
David Forbes, Tucson AZ
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