Category Archives: Electronics

I am conducting a seminar next week on cooling electronics. One of the topics I will cover involves basic heat sink usage. Most of the products that are designed by my team do not use heat sinks because we are not allowed to use fans in our designs – fan-based cooling systems generally have air filters that require regular maintenance that is unacceptable for optical hardware deep in the network (example deployment). Continue reading →

I just had another meeting where folks thought that specifications for Annualized Failure Rate (AFR), failure rate (λ), and Mean Time Between Failures (MTBF) were three different things – they are mathematically equivalent. I have given up writing the formulas down as a way to explain the concept. Maybe a graphic will illustrate the relationship better? I have tried this approach before – the most successful was about component temperatures. That graphic has saved me hours. Continue reading →

I was doing some reading on the Planet Analog web site when I encountered an interesting blog post by Dennis Feucht on a simple BJT-based voltage regulator with an output current limit. Continue reading →

I have been asked to write some requirements for an optical product that is powered using Power Over Ethernet (PoE). It has been a few years since I have worked on a PoE-based design, I thought it would be useful to review the standard and ensure that I still understand it. This is a good exercise in basic electrical design and will also illustrate how to design circuits using Mathcad utility functions that I have written over the years. Continue reading →

Our optical products are powered by AC power converters (e.g. wall adapters, uninterruptible power sources) that we buy from outside sources. Over the last two weeks, I have been dealing with a number of aluminum electrolytic capacitor failures in these power products. Like all components, electrolytic capacitors eventually do wear-out (e.g. Figure 1). Unfortunately, their lives are relatively short (~15 years) compared to other components in the system. We have had some of these power sources in the field for nearly ten years, so we are starting to see some worn-out capacitors. Continue reading →

While I am in management, I still get an occasional circuit design question – I really like these questions because the get me away from some of the monotonous aspects of management (i.e. budgeting). This morning a power supply designer stopped by and wanted to discuss an issue he was having with fixing an issue with an old design. I immediately dropped my budgeting activity and leaped into action. Continue reading →

I have an application that requires a thermal magnetic circuit breaker that will provide a given level of protection at an elevated temperature. Most thermal magnetic circuit breakers have a current rating that is specific to a stated temperature, usually room temperature (~23 °C). In my case, I need a circuit breaker with a 15 A break current at 50 °C Continue reading →