Bench Talk

Archaeologists will tell you that if you really want to understand a culture, go look in their landfills. All of their secrets and priorities are evidenced by what is found and what is not found in the city dump. The FBI is known to mine the trash of criminal suspects to build their cases. The question on my mind is - what is in your e-waste stream?

Seen any TV Repair Service trucks on your street lately? No? Have you ever taken a piece of electronics gear to a repair shop? Never? Really?? It's not that electronic equipment doesn't fail - it's just that the repair bill would likely exceed the cost of a replacement product. No one knows how much of the electronic trash in our landfills was put there because of technical obsolescence and how much was tossed before the end of its useful life because it failed.

One of the duties that falls to us geek-of-the-family types is playing the role of the IT Help Desk for friends and relatives. In my case, I try to maintain my parents’ computer and connections even though they live 600 miles away. Without the ability to just show up when things go wrong, I need bullet-proof solutions.

Like most professions, engineering has developed a language of its own. This is needed to convey very specific and precise information. Fuse design engineers, for instance, make a very clear distinction between an overload condition and a short-circuit condition. (Overloads are in the range of ~200% of the fuse's rating while short-circuits are 10X or more.)

Let’s face it - circuit protection can be a tough sell. Here’s why: 1) Circuit protection isn’t sexy. It doesn’t add any “wow factor to the product." 2) In fact, it doesn’t add any functionality to the product at all. 3) Any effect circuit protection has on the function of a device is likely negative. Adding capacitance, resistance or potential non-linearity to an I/O port is rarely useful in promoting high data rates. 4) It adds cost and can increase complexity. What circuit protection does do is provide some measure of reliability. It gives the end product the ability to sustain and likely survive potentially damaging electrical surges or contact with unexpectedly high voltages without exposing the user to electrical shock or becoming a fire hazard.

Have you ever thought about circuit protection as analogous to fire protection? There are lots of ways to prevent fires. There are active systems (fire sprinklers, automated extinguisher systems) and passive systems (self-extinguishing materials, self-closing fire doors) and safety-by-design systems where careful selection of non-flammable and insulating materials as well as physical layout make fire propagation nearly impossible. As it turns out, circuit protection has similar options. Here is an example of circuit protection via a safety-by-design technique...

When a piece of electronics fails, the manner in which that failure occurs is important and should be included in the design specification – especially for a consumer product. Most manufacturers realize that a UL (or ETL or other safety lab) Listing is a minimum requirement for product safety. But those requirements are focused on preventing fires and shock hazards. A piece of gear that fails in a plume of foul-smelling toxic fog, coupled with a few sparks or even a good ol’ firecracker report invokes a visceral reaction in the consumer that will absolutely guarantee that the replacement product will be a different brand. They just don’t want to experience that violent, scary failure again and will go out of their way to assure no repeat performances.

How many times have I heard that line? In future I’ll discuss the different classes of clients that circuit protection device manufacturers serve. But right now I’d like to offer up a real-world example of an application that most folks would never dream would benefit from circuit protection: Solar-powered walkway LED lights.

In this first post, I would like to talk a bit about the need for circuit protection in general. My view is that electronic devices should all have immunity to common surge events. That is to say, electronic devices should never fail due to ordinary and foreseeable electrical disturbances – be they ESD, induced lightning surges or incidental contact with AC power lines.