On 2/6/11 11:25 AM, will wrote:
Hey,
I just tested M.J.'s anode driver, with no luck. Performance is the
same. Also, the reason I don't need a resistor between MPSA92 and
MPSA42 is because (according to Jason Harper) the resistor between
MPSA42 emitter and ground forms a constant-current driver. Check out
http://nixietube.info/NixieTransistors.pdf, and go to the bottom of
page seven. I am using a 10k emitter-ground resistor. Per the advice
of this board, I replaced the 1 megohm resistor with a 10k resistor
and per my own advice I put another 10k resistor between the MPSA42
and microcontroller.
OK, I understand now. The current limit is in the emitter circuit. I
suppose that will work as well as the other - it's just a different
method. And it's true that you don't need a base resistor in that case,
since the base will be at 5V as the emitter voltage rises.
Silly me.
But photographs are essential, especially when the problem is "weird" as
this one is.
--
David Forbes, Tucson AZ
http://www.cathodecorner.com/
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