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All timeline stories.
We have a small group of active executive in SAE Manitoba Section. I served on the executive continuously from 1991 until I moved away from Winnipeg in 2011, and then reconnected with SAE Manitoba every time I was in the area.
In 2001, I was again Vice Chair for SAE Manitoba Section, and was honoured to be asked to go to SAE Leadership Development Seminar in Warrendale PA. Every session was different, and this was no exception… but it was always very worthwhile.
I was honoured to serve as Chair of SAE Manitoba Section a second time. Although it’s small, we have a great group of volunteers!
I was concerned about having to serve as chair for SAE Manitoba Section’s Governing Board, but I shouldn’t have been. With the help of all the other great people on the Governing Board, it worked out fine. We had an excellent year.
As Vice-Chair of SAE Manitoba Section, I attended the SAE Leadership Development Seminar in Warrendale PA. It was very helpful to put faces to the names of the people on the other end of the phone.
It was here that I saw the best innovation that I had ever seen, for an org chart: a small picture of each person beside their name. I kept that org chart on my wall for years, because as soon as I saw the picture, I would recall them clearly, and be able to work with them better. I’ve suggested many organizations since, to take up this idea of a visual org chart, but have never yet seen it done anywhere else. I’m sure somebody is doing it – but I haven’t seen it. I assure you, it works well!
We had turn signal flashers that that would misbehave from time to time, varying wildly, even though the math said it should work properly. I investigated.
It turned out that the supply to the main timing IC, a bipolar 555 timer, was reliant on the drop across the turn signal flasher… which itself varied as the turn signal flasher turned “on” and “off”! It was shorting out its own supply, essentially! Oh boy.
I developed a circuit that would allow the 555 timer to still drive the monster output transistor, the TO-3 cased 2N5301, but hold the IC’s supply during the “on” time. There were two problems with this – the circuit consumed too much current to be reasonably held up during the “on” time, and the output turned out to be referred to the wrong rail, in order to drive the output transistor using the same mechanism as before.
I addressed the current consumption by switching from the bipolar 555 timer to the then-relatively-new Intersil CMOS ICM7555. What a joy that it ran on almost no current!
Then, I developed a 2-transistor output drive to replace the 1-transistor stage. It worked well, until we ran it over temperature. It was then that I learned one of the fundamental lessons that I’ve taken through my entire career: do not rely on one transistor to “short out” second transistor’s base drive over temperature! It turned out that the Vce(sat) of the first transistor could exceed the Vbe(th) of the second transistor, sometimes, at low temperatures.
I found that you can short out the second transistor’s base drive, but then you need to put a resistor to the second transistor’s base, just to make it that much harder for the second transistor to turn on with leakage.
Well, that was a lesson learned, but then I just redesigned the stages to avoid that problem altogether. Once bitten, twice shy!
I did do some preliminary work on using a MOSFET output on the flasher, but I couldn’t make the short-circuit protection work, and decided to stick with the bipolar output. Later, a colleague, James White, took up that effort and successfully developed the “FET flasher”, which was another step forward turn signal flasher design.
Inspired by early instruction on statistical process control, I noted that we had ongoing continuous problems with the turn signal flasher flash rate and duty cycle. The flasher does two rates – turn, and hazard. To meet the SAE J590, there rates each have minimum and maximum rate limits, but also a minimum and maximum ratio between the two rates. We had constant ongoing high fallout rate on the production line, something like 30-50%, and were having to change component values continuously.
First, we did a process study. We took 33 units off of one batch and carefully measured their characteristics. When we analyzed them, to our surprise, we found that, although the spread of the rates was too wide to meet our requirements, it wasn’t that wide of a variation – it was primarily the process mean that was far off. The resulting Cpk did not perfectly meet our requirements, but it was close enough that we could improve our results considerably!
I undertook a careful analysis of the results of the study. I determined that changing the timing capacitor and resistor values, and using higher precision parts, should bring the results into J590 acceptable limits.
We ran another batch, and to our delight, almost every unit passed.
After that, I was still called upon periodically to address characteristics going outside the limits, but it was far less often. We found that often, this was as a result of batch-to-batch variations in the ICs or capacitors.
James White redesigned the “standard” 12 Volt turn signal flasher to use a MOSFET output, then he modified the design to successfully run on 24 Volts for bus & truck applications.
At about the same time that James was doing this, Can-Car Rail approached us to develop a 36 Volt flasher for their rail coaches. I thought it would be easy! Whoops, not so fast…
Well, oh my Lord, 36 Volts DC is nasty. My first attempt to just use my modified 12 Volt design was a complete disaster. The three lead-acid car batteries that we used for development just provided so much power that the 2N5301 output transistor overheated and failed on the first flash into a short. The 12V and 24V designs could flash into a short indefinitely (Ed Van Humbeck drove around with a flasher wired directly across his car battery for about 6 months in 1980/1981 to prove that it could easily handle it).
The FET Flasher didn’t perform any better.
Instead, I had to develop a completely different design, right from scratch. I used some of the same concepts, although I had to change components – the 2N5301, for instance, is only rated for Vceo to 40V, so it had to be changed. The supply to the 555 timer had to be modified to handle the high voltage. The drive stages had to be changed to handle the voltage translation and the drive requirements of the new output transistor.
The biggest change was that the 36V flasher got a “ground return connection”, which allowed it to be constantly powered, instead of having to scavenge the operating current from the bulb current.
We had to change the mechanicals as well – the original 12V and 24V flashers were simply placed into a plastic cap along with a heatsink/mount made of a piece of bent & punched aluminum, then the cap was filled with epoxy. The But, like all challenging designs, it was 36V flasher needed much better heat dissipation for several devices, so it was designed as a flange mount device, a circuit board mounted on top of the “W” shaped metal mount, then covered with a lid.
The design was a challenge, the result was a success, but we didn’t make many units – perhaps a few hundred. But, that’s the difficulty – you can’t tell ahead of time, what will be a winner, and what will be a loser. You just have to do your best, and take on the ones that look reasonable.
Ford New Holland had purchased Versatile Farm Equipment, brought some new products to the plant, and Vansco was providing much of the electronics that went into all of its tractors.
A new tractor was being made, which at the time was called “P53”. It needed a power distribution panel / fuse panel and turn signal flasher. I suggested that it could be a monster printed circuit board, and was asked to make it happen.
To accommodate differing standards worldwide, the turn signal flasher was a separate, small circuit board that plugged into a connector in the middle of the board.
Meanwhile, the main board was developed to fit inside one of the vertical window pillars. It was physically large surface area, and had a large metal bus bar down the middle to distribute power to the fuses. Of course, it had monster copper on it, 2 oz, and wide tracks, to ensure long life.