If anyone reading this blog has lived in the Midwest, let's say Indiana for instance, then you know that the weather changes as fast as your acceleration vector on a roller coaster at Six Flags. Many times, especially in the spring and fall, the weather can drastically change within minutes or hours. You may wake up on a September morning and step outside to a humid 90 degree day. You're chugging back 44-ounce Polar Pops from the local convenience store, wiping away what feels like a flooding stream of sweat from your brow; and then find yourself that night wearing long johns, sweatshirts, sitting by a fire, eating smores, and drinking hot chocolate.
We have all experienced drastic changes in our engineering life. As an engineer, the one thing that seems to change just as drastically as our Midwest weather is the opinions of Underwriter Laboratories (UL) or the other similar approval agencies. These agencies have plenty of opinions, requirements, understandings, and viewpoints about your PC board or system design.
Have you ever designed a board as part of a system that UL had approved — and then used the exact same PCB in a very similar system later on, only to have them reject it because the trace spacings were not correct? You find yourself with your mouth open so wide that your jaw is on the floor. You finally respond to the Codes Engineer: “What? You approved this exact PCB before on all previous systems.” The Codes Engineer responds, “Oh, well, we may have to go back and change all of those also.” Even though they have been in production for five years already.
I just never understood the unpredictability of UL and what test requirement they were going to come up with next. Sometimes, it's so frustrating that you just look at them and say, “WOW, REALLY? Do you really think my single 20mA LED system could fail and draw 20,000W, requiring me to throw a current-limiting resistor that would take up as much room as a medium-sized puppy? Why do I need 2.4mm PC trace spacing on a system rated at 250W or less when you approved my 1.6mm PC trace spacing on my previous 37 designs?”
Luckily, your design will only require a $2,500 paperwork change. Are there other engineers out there dumbfounded by the ever changing back-and-forth requirements? Are the changes really necessary, or is the code approval process just being done purely for business reasons?
Let me know your thoughts.