The conceptually simple idea to determine current by measuring voltage across a known resistor shows the subtle nature of design tradeoffs. Part 1 of this article looked at one important aspect of the choice of resistor value in current-sensing applications, but it was only the electrical impact. However, the thermal impact related to resistor I2R […]
A tradeoff case study: Sizing the current-sense resistor, Part 1
The conceptually simple idea to determine current by measuring voltage across a known resistor shows the subtle nature of design tradeoffs. There’s probably no phrase that misrepresents the realities of engineering design other than “hey, that should be no big deal.” Even simple-looking design decisions are often not so simple. The reality is that a […]
The basics of AC-line isolation for safety, Part 1: The challenge
Isolation from the AC line is essential for user safety in many situations and can be implemented using a special isolation transformer as well as other means. “Isolation” is one of those terms which gets tossed around and is often cited as an almost universal, all-purpose cure for various ongoing or possible circuit and system […]
Understanding stop/start automobile-engine design, Part 6: Responses and work-arounds
Stop/start operation is both complicated and controversial. Despite the sophisticated algorithms it employs, no algorithm is perfect under all conditions. In addition, there are some “human factors” issues with respect to driver expectations and even nearby pedestrians, which stop/start brings. Q: What are some “issues” with stop/start? A: First, there’s the issue of added vehicle […]
Understanding stop/start automobile-engine design, Part 5: Additional considerations
Thus far, we have looked at mostly non-electronic and mechanical implications of stop/start, such as requirements on the battery technology, the crankshaft, and the starter motor itself. There is also an impact on the vehicle’s power electronics and battery management system (BMS). Q: How does stop/start begin to affect the “electronics”? A: It begins with […]
Understanding stop/start automobile-engine design, Part 4: Mechanical wear issues
It seems “obvious” that starting and stopping a car’s engine repeatedly adds to stresses on the mechanical components and therefore shortens the life of the power train. But does it? The answer is “yes and no.” This part explores some of the underlying issues. Q: How many stop/start cycles are we looking at? A: Numbers […]
Understanding stop/start automobile-engine design, Part 3: The battery situation
The stop/start approach has significant implications for the car’s battery and battery management system (BMS). Q: How does the battery charge/discharge cycle function in a non-stop/start vehicle? A: In a car without a stop/start system, starting the engine is a one-time event for the duration of the trip. While the engine is running, it also […]
Understanding stop/start automobile-engine design, Part 2: The starter motor
The previous part of the article provided the context and rationale for stop/start operation in cars with internal combustion engines. This part will look at its impact on the starter motor itself. Q: Which vehicles need a starter motor and why? A: Electric motors do not need a starter, as they self-start and rotate when […]
Understanding stop/start automobile-engine design, Part 1: The idea
Today’s motor vehicles are vastly different compared to those of just a decade ago. This article will look at a relatively new “feature” (some say an unneeded and unwanted one) called “stop/start” which is increasingly standard on many internal combustion and hybrid electric vehicles (HEVs). Q: What is stop/start? A: It’s a simple idea, at […]
Even model railroads are now networked, Part 4: Battery power, maybe
The traditional model railroad power and control has transitioned from simple hardwired loops to advanced networking in the past decades, bringing many benefits and a few drawbacks. Batteries to the rescue, maybe It turns out that the advances in battery technologies such as high-capacity yet light rechargeable lithium-based cells are not only offering new approaches […]
