Tuesday, November 13, 2012

Big Dumb Science - Or How I Spent the Summer of '91 (Part 2)

The System

You can find the other parts of this here : Part 1 and Part 3

So that’s how I came to be working out of a guy’s basement in Vienna, VA. The EE who designed the board for the system was as inexperienced as I was, but was also fearless. Olga was an enigma. A heavyset hispanic lady (we were all too young back then) who looked more like a cleaning lady than the excellent engineer she was. She did know her craft and the motherboard she designed was almost perfect.  She was cheerful, upbeat, and never let Edwards or the job get her down. I have no idea what happened to her after Edwards shut down his company.

I say almost as any board fabrication is sure to have some glitches. The problem on this board took some sleuthing to figure out. I was attempting to get the serial port to work without much success. The data lines from the processor to serial driver chip were correct, but no serial activity could be seen on the output pins. I checked each line and it appeared to be correct.  I then looked at connector on the board more carefully and discovered that Olga had flipped the mask for the driver chip, reversing all the pins. The solution was easy: bend all the pins on the chip in the opposite direction and plug it in backwards. Score!

The code itself was all written in ‘C’, which was compiled using the TI toolset. It consisted of a few standard control features required by the chip and a ‘big loop’ style main loop. There was no real need for interrupt handling as there were no real time requirements. The sample phase would call the weather service, download the current indicators and place them in a table. It then would trigger and collect the value of the electrical charge for the ground sensor and place that in a table. The weather factors and the ground values would then be weighed and a ‘threat value’ would be obtained. The threat value drove the priming of the laser, which had various stages that had to be initiated before firing – such as starting the water cooling, turning on various stages, then culminating with firing.

The ground sensor was the one part of the system I couldn’t really test. In Virginia, electrical storms were relatively rare. Edwards house location was in a spot where the ground sensor could not be buried in such a way that good reading could be obtained. Thus, I was stuck with coding for an event that I would never see until we integrated the system at Ft. Huachuca.

As for the other parts of the system, those we were able to test. Firing the laser was done at office in Sterling that Edwards did a short term lease in. This was required as the three phase power required was not available in Edwards residential setting.  Per OSHA rules back then, there were administrative hurdles to firing the laser also. Each of us had to get an eye exam so that after the project finished, they could compare our eyes to assess if they had been damaged. Due to the events that unfolded, I never got that exam, but except for one case, I was never on any danger of an eye strike.

In that one event, I was debugging the startup sequencing and Edwards was testing the one part of the system that he alone designed – the fiber connection that would carry the laser out to a pit that would be constructed to receive the lightning blast. I had activated the laser and was reaching to put my protective glasses in place when Edwards turned around, fiber in hand, the beam bouncing off of every reflective surface in the room. Olga and I did some rather comical dodging and diving to avoid the very real chance of being burned or blinded by the beam. After all the dramatic representation of lasers in Star Wars and the movie ‘Weird Science’ I was amazed that the diameter of the focused beam was so small, yet also so potentially destructive.

So, system build ready, we packed it up flew with it to Arizona. I say we, when actually it was just Olga and I, as Edwards was still waiting on parts for his optical coupling design.

Next: Ft Huachuca

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