( Important schematic note: Q1/Q2 control bit A, Q3/Q4 control bit B, Q5/Q6 control bit D ( not C!), and Q7/Q8 control bit C ( not D!)).įor item 2, the Hours Reset circuit needs a few more parts. So, to count from 0 to 5 instead of from 0 to 9, we can use the transition of B from 1 to 0 to set C to 0. If you're trying to understand how the decimal counter circuit works from its schematic, note that it counts per the following pattern: So first, to count from 0 to 5, the 5212L-4A assembly(or 5212A-4a, or other variants) can be modified as follows: Disable the "Storage" feature of the Decimal Counter modules so that we can see the module counting.Modify the Hour LS (Least Significant) digit to reset to '1' instead of '0' (so that hours count from '1' to '12'.Add a reset circuit to the two "hours" digits such that, if the hour count increments to '13', it immediately resets the two hour digits.Change two of the counter modules to count from 0 to 5 (instead of 0 to 9), so that minutes and seconds would each count from 0 to 59, instead of 0 to 99.That manual, plus some scope probing of various signals within my 5233L counter, told me pretty much all I needed to know. A quick glance revealed that it had the all-important schematic for the decimal counter module (HP part number 5212A-4A - and although my counter used 5212L-4A modules, the 5212L-4A design seemed to be very close (if not identical) to that of the 5212A-4A)). HP used the same nixie "single-digit" decimal counter plug-in module in a variety of its counter products.
This really didn't prove to be much of a problem. But there was a small complication: I didn't have schematics for the 5233L. I then go to the local copier store (here it's the "Kinko's" chain) where I copy my "composite" drawing onto a B-size sheet (so that it's a single piece of paper, not two taped together).
If you don't have a light-table for accurately aligning them, a window works fine. My printer does not print B-size sheets, so I instead print two "A" size sheets, trim their edges, align them (note the alignment marks in the overlap area), and then tape them together so that they form a larger sheet. If the panel is larger than, say, 8.5 x 11 inches, you'll need to create a "B" size sheet (11" x 17"). Then, using an electronic drawing program (I use Adobe Illustrator, but others I know use Autocad), I accurately place all hole locations as well as any labels I want to add on my panel drawing. Here are the steps I follow.įirst, For the panel, I measure its dimensions and the locations of all holes I want to use. Here's a way to make it look more professional. There's a lot of surplus equipment out there that can be used as the basis for a homebrew project.
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