Leading 0 (10s hours) in direct drive of nixie clock - are stray effects any concern?

[Don Moore]

Hi - new to this group.  Brand new to nixies, and I have introductory experience with Panaplex displays.  I have a direct drive design that uses current sinks in each cathode connection.

It appears that with the nixie, the anode resistor supplies the current limiting function.  I am using Neonixie's 6-digit clock chip and design from 2006, linked to in a recent post here, that drives 74141s to drive the tubes using direct drive.  I believe the chip uses PWM to drive the tubes, but I don't know what the duty cycle or frequency is.  I am curious about determining the anode resistor value.

My tubes are Z5660M, which have a minimum recommended power supply of 170V.  Let's assume 180V.  The sustaining voltage is 140V.  The datasheet lists Imin = 3 ma, Imax =6  ma and Ipulse = 20ma.  Would a baseline to determine the anode resistor be to assume something in the middle like 4.5 ma, which would be about 8.9k at a 40V drop?  It seems like tweaking may be needed, and to simulate the actual PWM signal to see what intensity results, and see if the value needs to be increased or decreased.  Am I on the right track?  Thank you in advance.

Don

[Don Moore]

I apologize for the title of this post.  I changed the body without updating the subject.  I don't see a way to edit it.

[Paul Andrews]

8.9k would be correct for 180V. You don't need to figure in anything else for direct drive. If the software/hardware uses PWM to control brightness, it will still be expecting 8.9k resistors. If the display is actually multiplexed, that would be different.