Second-Order Systems, Part I: Boing!!
Jason Sachs takes the spring 'boing' of a doorstop into the math of second-order systems, using the series LRC circuit as a concrete example. He shows two standard transfer-function forms, explains why ωn only scales time while ζ sets the response shape, and derives pole locations plus an exact overshoot formula that helps tune embedded-system responses.
Introduction to Microcontrollers - 7-segment displays & Multiplexing
Seven-segment displays can eat dozens of GPIO pins and dozens of resistors, but multiplexing trades pins for time and cuts component count dramatically. Mike Silva shows a hands-on AVR C implementation with segment encoding, a 100 Hz display scan ISR, several integer-to-digit conversion techniques, and software workarounds for messy pin mappings. He also demonstrates a timer "leapfrog" to reuse one timer for two tasks and compares performance so you can choose the best approach for your MCU.
Someday We’ll Find It, The Kelvin Connection
Low-ohm measurements will fool your multimeter unless you use Kelvin connections. Jason Sachs walks through four-wire sensing using a current-limited supply and two DMMs, explains thermoelectric and connector-related errors, and shows why schematics and PCB layout must reflect Kelvin sense pads to avoid subtle measurement and circuit problems.
Practical protection against dust and water (i.e. IP protection)
Needing IP65 protection while exposing humidity and pressure sensors on a tight $15 budget, Dr Cagri Tanriover hunted for a practical fix. He found that an SHT2x humidity sensor with a microporous filter cap and O-ring provides IP67-level protection, and by matching a pressure sensor that fits the same cap he met and exceeded the IP65 requirement. The post shows a low-cost, component-level workaround.
10 Items of Test Equipment You Should Know
Jason Sachs walks through ten often-overlooked pieces of test gear that make debugging embedded hardware faster, safer, and more precise. From clamp-on and Rogowski current probes to spring-tip probes, IC test clips, and compact DAQ systems, each tool targets a common bench frustration. Practical buying notes and use cases help you choose tools that save time and reduce guesswork.
A wireless door monitor based on the BANO framework
Fabien Le Mentec built a battery-powered wireless door monitor and a reusable node framework called BANO to monitor doors across seven floors without wired links. The post highlights BANO's 17-byte key,value protocol, the node runtime that enables wake-on-interrupt low-power operation, and practical RF choices like the NRF905 plus a 330 µF cap to handle coin-cell transmission peaks. It includes source, PCB, and base station notes.
First-Order Systems: The Happy Family
Jason Sachs takes the modest topic of first-order systems and makes it useful, showing how RC filters behave in both time and frequency domains and why they all share the same shape. He steps through step, ramp, and sinusoidal responses, explains poles, zeros, and Bode behavior, and uses Python plots to make tracking error and the role of tau easy to visualize.
Lost Secrets of the H-Bridge, Part IV: DC Link Decoupling and Why Electrolytic Capacitors Are Not Enough
Switching H-bridges can kick nasty voltage spikes onto the DC link, and a single electrolytic capacitor rarely fixes the problem. Jason Sachs uses simulations and practical PCB layout advice to show how a three-tier decoupling strategy — bulk electrolytic, mid-value ceramics or film, and many small HF bypass capacitors plus PCB plane capacitance — tames spikes, reduces EMI, and avoids harmful resonances when parts and vias are placed correctly.
How to Analyze a Differential Amplifier
Jason Sachs walks through the algebra and intuition behind the classic four-resistor differential amplifier. He derives the exact output equation, isolates error terms from resistor mismatch and op-amp imperfections, and explains why common-mode gain depends on mismatch not on the differential gain. Read this for clear formulas, modal insight into common-mode versus differential-mode, and practical steps to reduce offsets in real designs.
Efficiency Through the Looking-Glass
Efficiency numbers can be misleading, Jason Sachs argues, because they hide the real cost engineers pay in wasted watts. This post flips the focus from percent efficiency to absolute power loss, shows how losses often stay nearly constant across loads, and walks through a practical thermal method to measure those losses more reliably than subtracting input and output power. Read it to rethink how you budget heat and energy in designs.
Better Hardware Design Decisions, Faster: A Lean Team’s Guide to MDO
As design complexity grows, siloed decision-making often leads to late-stage surprises, costly rework, and missed opportunities for optimization. Multidisciplinary Design Optimization (MDO) offers a structured approach to solving this by enabling teams to evaluate trade-offs and impacts across the full system before implementation begins. Traditionally used in large, high-budget industries like aerospace, MDO is now within reach for lean teams, thanks to more accessible modeling tools and an urgent need for tighter collaboration. This article outlines how small hardware teams can adopt MDO in a practical way, starting simple, integrating key models early, and building toward a culture of systems thinking. The result is better design decisions, faster development, and more robust, manufacturable products with fewer surprises along the way.
Optimizing Optoisolators, and Other Stories of Making Do With Less
Jason Sachs digs into how to squeeze speed and reliability from low-cost optoisolators, showing practical tweaks that often outperform default datasheet usage. He mixes hands-on circuits — using 4N35 base-emitter resistors, Schottky clamps, input speedup caps, and output buffering — with transistor-switching theory and a cautionary production story to show when to optimize and when to splurge on pricier isolators.
10 More (Obscure) Circuit Components You Should Know
Jason Sachs follows up his earlier primer with ten more underused but practical parts that can simplify embedded hardware designs. From MOSFET-based ideal diode controllers that eliminate diode drops to TAOS light-to-frequency sensors that expand dynamic range, the post explains what each component does, when to choose it, and real-world tradeoffs learned from field use. Ideal for engineers looking to broaden their parts toolbox.
Unmanned Ground Vehicles - Design Considerations for Snow and Cold Environments
Winter conditions expose UGV weaknesses: snow, ice and extreme cold change traction, sensor performance, batteries and lubrication. This post walks through snow mechanics, ground-pressure tradeoffs for wheels versus tracks, and practical mitigations like heaters, insulation, sensor covers and low-temperature lubricants. If you design autonomous ground systems for cold climates, these engineering checks and referenced studies will help you avoid mission-ending failures.
Which MOSFET topology?
Jason Sachs breaks down the four basic MOSFET topologies for switching a two-wire load, showing why low-side N-channel is usually the simplest and cheapest option. He explains why grounding or chassis return can force a high-side switch, how P-channel devices trade performance for simpler gate drive, and why high-side N-channel options need extra driver circuitry. He also stresses adding freewheeling diodes for inductive loads.
Improving the Reload2 active load
Fabien Le Mentec takes a low-cost Reload2 active load and turns it into a programmable test tool. By swapping the manual setpoint for a Teensy 3.1 DAC and replacing the op-amp with a chopper amplifier, he gets software-controlled current profiles and lowers the minimum load current to about 7 mA. It is a practical hack for testing power supplies and Ethernet-powered boards under realistic startup and sleep conditions.
On optimizing manual soldering
When faced with manual soldering of thousands of components, speed and efficiency become pivotal. Here are some takeaways from my own experience attempting to optimize such a process.
Byte and Switch (Part 1)
Driving a 24V electromagnet from a 3.3V microcontroller looks trivial, but Jason Sachs shows how that simple switch can fail spectacularly. He walks through the cause of MOSFET destruction when an inductive load is turned off, and explains the practical fixes you actually need: a flyback diode, a gate series resistor, and a gate pulldown to keep the transistor well behaved.
Software is free and can right any wrong
Software changes are so much easier than hardware modifications, so the temptation is always to take this approach to fixing bugs. This may not always be a good idea.
A Useful Current Profiling Method
Dr Cagri Tanriover shares a practical, low-cost way to capture millisecond-scale current profiles when you do not have a DSO. The method uses a 0.3 ohm shunt, an LM324 amplifier with roughly 11x gain, and a microcontroller ADC to log 10-bit samples at 20 kHz, giving sub-millisecond timing and about 1.15 mA sensitivity for embedded radio measurements.
Hot Fun in the Silicon: Thermal Testing with Power Semiconductors
Bringing hundreds of amps into the lab for low-Rds(on) MOSFET thermal tests is impractical. Jason Sachs demonstrates a clever workaround using a zener diode, a series resistor, and a constant-current lab supply to dump the same watts into the device at much lower current. He also explains how to use datasheet RθJC values and type T thermocouples to estimate junction temperature and size heatsinking or airflow.
Video-Based STEM Embedded Systems Curriculum, Part 1
This curriculum shows how to teach introductory embedded systems using free online videos and low-cost kits, suitable for middle-school, high-school, college, or adult learners. It packages curated educator recommendations, a per-student equipment and book list, essential free software, and core lesson topics like Arduino, MicroPython, Kicad board design, soldering, and RTOS basics. The approach stresses hands-on labs, safety, backups, mentorship, and adapting to local budgets.
Turn It On Again: Modeling Power MOSFET Turn-On Dependence on Source Inductance
This is a short article explaining how to analyze part of the behavior of a power MOSFET during turn-on, and how it is influenced by the parasitic inductance at the source terminal. The brief qualitative reason that source inductance is undesirable is that it uses up voltage when current starts increasing during turn-on (remember, V = L dI/dt), voltage that would otherwise be available to turn the transistor on faster. But I want to show a quantitative approximation to understand the impact of additional source inductance, and I want to compare it to the effects of extra inductance at the gate or drain.
Efficiency Through the Looking-Glass
Efficiency numbers can be misleading, Jason Sachs argues, because they hide the real cost engineers pay in wasted watts. This post flips the focus from percent efficiency to absolute power loss, shows how losses often stay nearly constant across loads, and walks through a practical thermal method to measure those losses more reliably than subtracting input and output power. Read it to rethink how you budget heat and energy in designs.
Improving the Reload2 active load
Fabien Le Mentec takes a low-cost Reload2 active load and turns it into a programmable test tool. By swapping the manual setpoint for a Teensy 3.1 DAC and replacing the op-amp with a chopper amplifier, he gets software-controlled current profiles and lowers the minimum load current to about 7 mA. It is a practical hack for testing power supplies and Ethernet-powered boards under realistic startup and sleep conditions.
Intel 8088 - A blast from the past
The Intel 8088 is a reminder of how hands-on early microcomputer work really was. This short retrospective looks back at wire-wrapping, perfboard construction, and assembly language programming on a board built around the 8088 and its support chips. It is a fun contrast to today’s Raspberry Pi era, where far more performance comes in a sealed package you can’t build yourself.
What is Pulse Width Modulation and How Does It Work?
Pulse Width Modulation (PWM) is a technique used to control the average voltage supplied to a device or component by adjusting the width of a series of pulses. It works by rapidly turning a signal on and off at a specific frequency. The crucial element of PWM is the duty cycle, which represents the percentage of time the signal is “on” (high voltage) compared to the total time of one cycle.
Troubleshooting notes from days past, TTL, Linear
Troubleshooting electronics is more about thinking than tools, yet details matter. This concise collection of technician notes condenses practical procedures and probe precautions, IC failure modes, digital logic diagnostics, and common power-supply traps. Drawn from classic guides by Frank R. Dungan and James Perozzo, it provides a methodical checklist to isolate faults faster and avoid costly mistakes when repairing embedded hardware.
A simple working I2C (TWI) level shifter
When interfacing 3.3V and 5V boards, Dr Cagri Tanriover shows a no-fuss MOSFET solution to keep I2C talking across voltages. The post walks through using the NXP MOSFET level-shifter idea with BS170 transistors and 10 kΩ pull-ups, notes it ran at 400 kbps for his setup, and includes a quick four-step test to verify the build before connecting microcontrollers.
Metal detection: building the detector
Fabien Le Mentec turns a bench-validated BFO stage into a field-ready metal detector using scavenged parts and straightforward fabrication. He moves the circuit from breadboard to a through-hole prototyping PCB, swaps the Arduino Nano for a lower-power Mini, and builds an ABS control box with buttons and a buzzer. The build uses a 2S LiPo pack with a 5V LDO and a nonmagnetic coil mount, with practical notes on tradeoffs and safety.
