标签: LIGHTS

I saw something I never expected to see on the way home a few evenings ago -- a set of traffic lights that had failed with all of them showing green.   By the time I arrived at the junction in question, there were police cars with their lights flashing all over the place, policemen standing in all four branches of the intersection, and a number of cars (or pieces thereof) piled up at the sides of the road.   That must be a horrible experience -- entering a junction brimming with confidence that you have a green light, and meeting cars coming from your right and left whose drivers also think they have right of way.   I remember them waffling on about this at university -- how to design systems so that they always fail into a known state. As I recall, they used traffic lights as an example, with the design being such that they would always fail to all red; never to all green.   But that was 35+ years ago now and -- like so many other things -- it's faded from my mind. Let's assume the simplest case of two roads crossing at 90 degrees (North-South and East-West).     Do you remember how to create this sort of design such that it will only fail with both directions red (or off)? And can you conceive how the lights I saw yesterday evening had managed to fail with both directions green?   Max Maxfield

My father and I jokingly share that the main reason for divorce in the US has to be putting up the Christmas tree (specifically, stringing lights). Each year it is about the most painful four hours of my life. It only takes about two hours to string all the lights on our nine-foot tree, but I inevitably dedicate another two hours to replacing burned-out bulbs and identifying dangerous strands or sockets (side note: our family can't stand the flicker associated with LED bulbs).   Worst connectors ever! Christmas tree light sockets have to be the worst connector ever designed. First, they are nearly impossible to remove. The bulb base fits almost flush into the socket. There's no lip or feature to pull on—enter broken and bloodied fingernails. Plus, the retention has to be in the hundreds of pounds. I often find I need surgical tools to remove them. Second, they provide for ridiculously poor and unreliable contact. About a quarter of the bulbs that are out just make poor contact and removal/reinsertion fixes the issue. Third, they're all just different enough that they aren't interchangeable. I have a collection of bags with different types. I inevitably have to swap bulbs between base types. That's a plus—at least the bases are easy to swap. This got me to thinking, what makes a good connector? This may sound obvious, but do connector designers have guidelines or best-practices? I would recommend the following: Electrical performance. This goes without saying. Most connectors do this well, matching the electrical properties for the application. Ease of assembly. Make the connector easy to assemble (by hand or automated) with minimal special tooling. Ease of disassembly. See No. 1 above. Usually neglected because, well, most connectors don't have to be disassembled. Ease of connection/separation. Use simple locking features that make connections quick and easy. Reliability. Both electrical and mechanical... make sure it holds up to the environment. Compatibility. I realise there is a marketing component to this, but the more "open" and compatible a connector standard is, the better.   Todd Marcucci VP Research Development Good Earth Energy Conservation Inc Note: This article appeared in 2012 on The Connecting Edge, but the connector problems remain.

The No. 1 cause for divorce in the US has to be putting up the Christmas tree (specifically, stringing lights). Well, that's just a joke between my father and me. Each year it is about the most painful four hours of my life. It only takes about two hours to string all the lights on our nine-foot tree, but I inevitably dedicate another two hours to replacing burned-out bulbs and identifying dangerous strands or sockets (side note: our family can't stand the flicker associated with LED bulbs).   Worst connectors ever! Christmas tree light sockets have to be the worst connector ever designed. First, they are nearly impossible to remove. The bulb base fits almost flush into the socket. There's no lip or feature to pull on—enter broken and bloodied fingernails. Plus, the retention has to be in the hundreds of pounds. I often find I need surgical tools to remove them. Second, they provide for ridiculously poor and unreliable contact. About a quarter of the bulbs that are out just make poor contact and removal/reinsertion fixes the issue. Third, they're all just different enough that they aren't interchangeable. I have a collection of bags with different types. I inevitably have to swap bulbs between base types. That's a plus—at least the bases are easy to swap. This got me to thinking, what makes a good connector? This may sound obvious, but do connector designers have guidelines or best-practices? I would recommend the following: Electrical performance. This goes without saying. Most connectors do this well, matching the electrical properties for the application. Ease of assembly. Make the connector easy to assemble (by hand or automated) with minimal special tooling. Ease of disassembly. See No. 1 above. Usually neglected because, well, most connectors don't have to be disassembled. Ease of connection/separation. Use simple locking features that make connections quick and easy. Reliability. Both electrical and mechanical... make sure it holds up to the environment. Compatibility. I realise there is a marketing component to this, but the more "open" and compatible a connector standard is, the better. We've all had dealings with questionable connectors. Maybe it was at a previous job or on a previous project. We've all used a connector at one point or another that made us think "What was that engineer thinking?" What are some of your "worst connector ever" experiences, and what additional best-practices do you think there should be? Todd Marcucci VP Research Development Good Earth Energy Conservation Inc Note: This article appeared in 2012 on The Connecting Edge, but the connector problems remain.