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Category Archives: Electronics
I presented a seminar over lunch today on short-range DC power distribution, which I believe is one of the most exciting areas in electronics today. AC power distribution has dominated power engineering since the "War of the Currents" ended with Westinghouse's AC system winning a decisive victory over Edison's DC system back in the 1890s. Starting in 1930s Europe, high-voltage DC distribution has slowly gained a foothold in some long-haul, high power distribution applications, but most power distribution has continued to be dominated by AC. Continue reading
While reading about how these units worked, I noticed that the amount of surge voltage they let pass (called let-through voltage) is a function of the hookup wire length. The units are tested with a hookup length of 6 inches, and the user is warned that the let-through voltage increased by ~20 V per inch of additional wire. I became curious about the origin of this rule of thumb. In this post, I will show you where this rule of thumb comes from. Continue reading
I have been sitting in a meeting on a high power version of Power over Ethernet (PoE) known as IEEE 802.3bt. It supports 90 W of output power with a guarantee of 71 W at the load. During the talk, Figure 1 was discussed (my version of the chart). When I am given some mathematical information, I like to experiment with it to see if I understand what I am being told. Continue reading
One of the most common computation tasks that my customers face is estimating battery capacity based on the battery's temperature and discharge current. Figure 1 shows a example of the capacity curves for a typical lead-acid battery. Ten years ago, I chose to implement this function with an Excel spreadsheet that used a polynomial approximation for this function. An engineer today asked me to explain how my Excel implementation works, and I felt this would be a good topic for a post. This approach is implemented using SUMPRODUCT – no helper cells were required. Continue reading
Quote of the Day If you don't stick to your values when they are being tested, they're not values; they're hobbies. — Jon Stewart Introduction I received a circuit design question from a reader who was asking how to design … Continue reading
Many electronic systems are required to generate an alarm when they detect their power failing – the alarm is referred to as a "dying gasp". These systems are required to generate a dying gasp alarm when their input voltage drops below a specified level. Continue reading
I have been designing circuits since I was a boy, and my passion for circuits has only grown over time. My home designs focus on sensor interfaces that I hook up to the Internet using Raspberry Pie and Arduino digital interfaces. These open-source HW interfaces make it possible to create incredibly powerful designs at home. Continue reading
Because I have had to deal with lightning in all sorts of contexts (e.g. military equipment, commercial hardware, consumer products), I have developed an enormous respect for the power of lightning (Figure 1). Because of this respect, I have worked to ensure that my own home has excellent lightning protection, including a sophisticated ground system. Even with all my precautions, last weekend lightning struck near my home and caused my garage door to open – letting rain into the garage, and my garage door opener to become unresponsive. Fortunately, I just had to cycle power again on the garage door opener and it started to work. Continue reading
I was asked this morning about how to create a 3D plot in Mathcad that shows a surface, two lines on the surface, and marks the point of intersection of the two lines (Figure 1). It just so happens that I have been looking at the amount of current that a PCB trace of a given area can carry for a given temperature rise above ambient. While the curve itself is a bit boring and viewing it in 3D does not add any value, this example does illustrate the procedure for generating this type of plot. Continue reading
The popularity of Power Over Ethernet (PoE) has proven that customers find value in using a single cable for both data and power distribution. Unfortunately, copper-based Cat 5e/6 cable is limited to a 100 meters because of data transmission issues. To circumvent this limit, some equipment vendors are using composite fiber/copper cables – a single cable that contains fiber for data and large gauge copper wire for power distribution (Figure 1). Continue reading