Thanks all for the wonderful input and confirming cathode current limiters
is a valid replacement for passive anode current limiting, even though the
latter is far more common. Despite the active cathode current limiters
requiring more parts and cost, the benefits are worth it for the projects
If you want to make this rock-solid, the pulldown resistor can be
calculated knowing the max tristate leakage current (usually 10uA) and
ensuring that 10uA of leakage does not produce enough base-current to turn
on the transistor.
Worst-case, you will have a transistor with infinite
On Saturday, November 11, 2017 at 10:45:00 PM UTC, Phill Scanlon wrote:
>
>
> Once again Jon you have been of great asistance and is very much
> appreciated.
>
>
No problem - happy to help. Enjoy playing with your dekatrons!
Jon.
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One other thought Allen...
What I believe is a simulation schematic shows 1 meg pull-downs on the base
lines. These may not be necessary depending on other elements of your
circuit in the real world.
My current design uses 595 shift registers and the outputs are high-Z when
disabled (Output
