Resistors are Futile - Friday Faux Real Stories

 

Welcome to another Faux Real Story on the Genuine Faux Farm blog!  This week, we're going to take you back to a time when the farmer was not a farmer.  Instead, he was a programmer who worked with software that was used to design printed circuit boards.

It was my first full-time job as a computing professional after graduating with my Bachelor's degree in Computer Science and Mathematics.  I had been hired to be part of the Government Avionics Division of Rockwell-Collins in Cedar Rapids, Iowa.  I still vividly remember arriving for my first day at the south entrance of Building 105 and being met by my immediate supervisor, Jerry.  As we walked past some of the entrance office area, that included (believe it or not) a pharmacy and travel agency, and entered the main part of the building, Jerry said, "Remember how to get back to this hallway.  Then you can always find a way back out of the building."

Jerry was not kidding.  Building 105 was actually a complex of buildings and I could see a pinprick of light that represented the far end of the wide hallway we were in.  This particular hallway was wide enough that managers in power suits could been seen walking one way and a forklift carrying a pallet could be going the other way.

Recent satellite image of complex including Building 105

There were various offices tucked into corners and there were computer labs, development labs, storage areas and assembly lines (mostly in the western portion).  It was incredibly easy to take a few turns and no longer know which way was up - much less out.

My job was to help maintain an older CAD (Computer Assisted Design) system that was used to design printed circuit boards.  Things that might look a bit like this:

The whole point of a CAD system was to give a designer a bit more flexibility in moving and visualizing components and making connections as they considered design options.  They could select from a long list of possible components - various capacitors, chips, jumpers and resistors - and position them on the board.  Some programs could be run to help route the circuits and generate the documentation required by the government.

These designs could then be implemented on the manufacturing floor using the various types of equipment.  Some of the newer automated equipment of the time included Surface Mount Technology (SMT) and Wave Soldering.  

One of my projects was to gather the coordinates and placement of simple components (capacitors and resistors) and put them into a computerized file format so that a new "chip shooter" machine could automatically place these components onto circuit boards.  The circuit board already had holes drilled to receive these components at their proper X,Y location.  It would move the board around until it lined up for the "shooter" to put the component into that spot.  This new equipment probably could place somewhere in the neighborhood of eight to fifteen components per second on a given printed circuit board.  In other words, it moved pretty fast.

Here is an example of a chip shooter in action.  This type keeps the board in place and moves the "shooter" around - it's probably for higher precision components that need a bit more care.  The one I saw moved the board to a "shooter" that was stationary.

What I recall seeing was a bit more like this one.  Go to the 57 second mark to see it in action.

In any event, my job was to identify items that could be loaded by the chip shooter in a printed circuit board design.  Then, the program I wrote would take the X,Y locations and the orientation (angle and depth) and place them into a format this piece of equipment could read.  

On the day of the big "first test," I went to the manufacturing lines where I was greeted kindly enough, but in a typical way line workers might react to one of the "educated pups" that worked on those @#$&(! computers.  The good news is that I didn't act like many of those pups tended to - but that still didn't mean they couldn't have some fun on my behalf.

One guy looked at me and asked where my helmet and safety glasses were.  Of course, I had none because no one had informed me that I needed them.  They found me a helmet that was a bit too big and some glasses before we loaded up the file to watch the machine work.  I think they were expecting me to ask why I needed the safety equipment - but I already had an inkling that something was up.

The machine took a while to set up, but once it was ready it pulled in a circuit board and hammered in a series of components and then it moved the board out of the way.  For good measure, it then SPIT another component out that bounced off the floor and flew off to the side.  While it was unlikely that it would have shot up at an angle to hit me in the face, it was not impossible.  Hence, the explanation for the safety equipment.

I am certain they could have stopped the machine then.  But, they decided this was too much fun and let it run a few more boards before shutting it down.  Each board was loaded up properly and then an extra resistor would get sent to the floor below - Zzzziiiing!

Of course, I got some good-ribbing after that because there was a problem with the data I had delivered to them.  I apparently took it well enough because I was invited to eat lunch with them afterwards.

So - what had happened?

Well, a CAD system allows the designer to grab an image that is a component and place it on the screen.  ANYWHERE on the screen.  This includes places that are not actually ON the circuit board.  So, the designer could pick a component, put it on the edge of the screen so they can grab it later and move it into place.  

Except this particular design had an extra component that the designer had left on the side of the screen - either by accident or on purpose.  My program grabbed every resistor and capacitor that was in the design file for any given circuit board.  It very diligently recorded ALL of them, including the one that was set off to the side of the board.

So, the chip shooter was also diligently following the instructions and trying to put this extra resistor where it belonged - off to the side of the board and onto the floor. 

I will say this, resistors are futile when you try to put them off the edge of a board.  But they make for a good story.