Original publication date: November 1991 Heurikon Historical Highlights A series of articles for The Horizon Arrow Sign Company Inc. Our first product development contract came from the Arrow Sign Company Inc., a Chicago advertising firm. Arrow’s Bob Scadron heard about us from a Madison-area relative who knew we were one of the few companies venturing into the new world of micro-computers. Bob drove up from his office one day and asked us to quote on building the computer controls for outdoor advertising message boards, very much like the one American TV has in front of their store today. Bob agreed to provide the lamps, sockets, and sign panels, but we had to figure out how to wire and control over a thousand light bulbs, and make the display show words using special visual effects. We were a low-overhead three-person operation back then, so our quote (only $3,500 for the engineering and $5,782 for the hardware) was attractive. We signed the contract in early 1975, just a few days after moving from Chris’s basement to a “real” office at 700 West Badger Road (another basement).
Do-It-Yourself Purchasing For the control unit, Chris designed an elegant CRT/keyboard terminal, complete with dark walnut side panels. Chris usually handled our purchasing, but when it came time to get a CRT for our terminal, John Burdick simply drove down the road to American TV and bought the cheapest portable black-and-white television set he could find. We removed the case, unhooked the tuner, and mounted the guts in our own enclosure. (In hindsight, maybe we should have left the tuner connected — we would have had the industry’s first combination data terminal and TV set!) The microprocessor was an Intel 8080 running on our MLP-8080 board (described last month). We designed a special 16-line by 32-character video display controller that could also display a duplicate image of what the outdoor sign was showing in a dot matrix area at the top of the CRT screen. As usual in those days, we wire-wrapped our prototype designs (in this case, the display controller and memory expansion boards), so we could easily make changes. Today, we still use the same green wire for our ECOs, but back then most changes were just put onto our boards with the rest of the wires. The electronics at the sign itself consisted of timing and control circuits, latches for the lamp data, and a triac (an electronic switch) for each lamp. We designed a high-speed communication interface so one coaxial cable could transmit data to the sign in real-time, and we figured out how to transmit nine-bit data using an eight-bit serial chip. John came up with a shrewd way of isolating our electronics from the high voltage lamp circuits; we wound our own small pulse transformers.
I wrote the application program in assembly language, one line per CPU instruction. It had a real-time portion that was in charge of computing the lamp states for each new image and serially transmitting the data to the sign at the right instant. A background task allowed the operator to type in and edit the message text and specify transition effects (e.g., travel, wipe, scroll), transition speeds, lamp brightness, and so on. One unique application problem we solved was keeping the messages readable when they were traveling across the sign. As the lamps were turned off, the long-life filaments faded out slowly, so moving letters appeared to smear unless we temporarily reduced the brightness of the lamps. The sign at American TV works that way, too.
During testing, we would often turn on the sign in our shop to check the operation of the lamp drivers. However, if we tried to activate all of the lamps at the same time, the system would consume over 30,000 watts of power and trip the main circuit breaker. As we approached the power limit, the power lines in the wall would hum, and the room temperature would rapidly shoot up past 100 degrees. That was fine during the winter months since we didn’t have any heat in the office (the heat we did get came through the ceiling from the apartments above), but it wasn’t much fun in the summer. When “ROM” Means Remember-Only-Momentarily One of our most nasty technical problems was with the ROMs. Unknowingly, we had been shipped a batch of defective parts from National Semiconductor. The read-only-memory chips either wouldn’t program completely or they’d get a bad case of amnesia and lose their contents after only a few days — and National denied it was their fault. After weeks of frustration, National finally admitted that other customers had complained, too. They checked their records and found they had shipped us parts from the reject pile. We learned that big companies could make big mistakes.
The prototype sign was installed at Jerry’s Fruit Market, not far from Chicago’s O’Hare airport. When we tried the sign at the site, the lamps would randomly flicker or not come on at all — it looked awful. While Bob paced, we huddled. Soon, we figured out what was wrong. We had used the single-phase power circuits in our Badger Road office to test the sign. In Chicago, however, the power was three-phase and parts of the sign were connected to different power feeds. As a result, the brightness control logic had the wrong timing reference. To fix it, we had to rework our timing logic and rewire part of the sign.
Satisfaction and Success It was exciting to watch the sign operate, knowing that Heurikon was responsible for the entire system from keyboard to lamp. The sign was highly visible, and it performed an obvious and valuable service. One otherwise ordinary airplane trip was made memorable when we flew within easy sight of the glowing sign while approaching O’Hare.
Although its original design life was five years, the fruit market sign helped sell apricots and strawberries for almost 13 years. As I look back, this was our “premier” systems project. It came early in our history, and it embodied all of the interesting and good things we’ve ever done. We solved many electronic, mechanical, manufacturing, and business problems while designing and building the signs. I visited the fruit market sign occasionally during the ’80s; each time it was like seeing an old friend. NEXT MONTH: Heurikon goes hog wild. |
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