PDP-10 KI10 panel - assembling BlinkenBone electronics
KI10 and BlinkenBone
A lot of electronic is needed to make the KI10 a full BlinkenBone device (see here for the different components).
When counting the various inputs and outputs of the KI10 panel, I found that I was extremly lucky: I could control everything on the panel with 3 BlinkenBoards, and over 95% of their inputs and outputs were in use. The early decision to drive 40 inputs and 88 outputs with one BlinkenBoard proved to be almost prophetic.
The whole electronic consists of
- one PC power supply
- one BeagleBone
- one BlinkenCape
- three BlinkenBoards
- one special microcontroller assembly for all the queer analog controls on the upper panel (see next page)
- lots, lots, lots of wires
To find a mechanical concept, all these components were reordered again and again. Suddently this pattern appeared and was fixed:
A single U-shaped metal plate was screwed against the backside of the KI10. Its lower segment provides a solid stand and holds the BlinkenCape with BlinkenBone, the middle segment is mounting platform for power supply and BlinkenBoards, the upper segment is used for fixing all the cables.
All lamps and LEDs are connected to a common supply voltage rails. The individual wires are switched to Ground with ULN2803 low-side drivers on the BlinkenBoards. So +12V and +5V are routed from the PC power supply to the "Lamp&Button" boards, and all BlinkenBoards have the same input/output drivers, whether they drive +5V LEDs or +12V light bulbs. The LED resistors were made pluggable, each one on it's own little PCB.
Making net lists
First I had to made detailed wire lists: which lamp is accessible over which connector? The DEC documentation was no help. I put labels and pin-counting rulers onto the DEC connectors and stressed my circuit tester:
The netlist is now part of the Blinkenlight configuration file, see attachement below.
Plugging and Crimping
Since the pure amount of wires could have killed me, I had to find a wiring technology with minimal work load. Crucial where these ideas:
- A friend made "FlipChip-to-pin-header" adapters for me. So I could connect plain flat cables directly to the ancient DEC connectors on the "Lamp&Button" boards.
- I crimped connectors to the other end of the flat cables. So the cables can be plugged onto the pin headers on the BlinkenBoards, which in turn are directly connected to the output /input drivers.
- To order all the resulting flat cable stripes, a horizontal plate serves as platform for cables and cable tiers ... like a cable channel. The need to order all the cables scales up exponentially with wire count!
Crimp whenever possible!
The whole connection matrix is contained only in a big cable tree, no connection logic is put onto the BlinkenBoards. And very less soldering is needed. It was the first time I used crimp connectors, and it was all fun. I like to work totally "cold" (no soldering), and testing individual connections is much easier compared to have a big bulk of wire-wrap on the BlinkenBoard patch field. And as I blew one register IC (there's so much +12V around), I easily could swap-in a new BlinkenBoard as replacement.
Here working in the museum of my computer club: Crimping is fun!
It was also fun ordering the cable into nice patterns:
This looks much better than my first BlinkenBoard project
The whole project needed 10 weeks, every free hour went into it. I was ready with wiring just in time: the last crimp contact was set on January 1st 2013, exactly 0:05 ... just when outside the firework started!