Here Comes The Noise!
Noise. That awful thing which nobody wants that most sadly never learn about. It's time to change that with this blog post.
7 Essential Steps for Reducing Power Consumption in Embedded Devices
Reducing the amount of power your embedded device is consuming is not trivial. With so many devices moving to battery operations today, maximizing battery life can be the difference between a happy, raving customer and an unhappy one that ruins your company's reputation. This post explores seven steps for optimizing your embedded systems' power consumption. You'll gain insights into the steps and techniques necessary along with receiving a few resources to help you on your journey.
Lost Secrets of the H-Bridge, Part V: Gate Drives for Dummies
Learn the most important issues in power MOSFET and IGBT gate drives: - Transistor behavior during switching - Calculating turn-on and turn-off times - Passive components used between gate drive IC and transistor - Reverse recovery - Capacitively-coupled spurious turn-on - Factors that influence a good choice of turn-on and turn-off times - Gate drive supply voltage management - Bootstrap gate drives - Design issues impacting reliability
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.
Modeling Gate Drive Diodes
This is a short article about how to analyze the diode in some gate drive circuits when figuring out turn-off characteristics --- specifically, determining the relationship between gate drive current and gate voltage during turn-off of a power transistor.
Make Your Own MCU Boards (2023 Teardown Conference)
Ditch the development boards! Products like the Nucleo development boards serve a wonderful purpose, but they’re ill-suited for projects that need to be small and cheap, such as hobby projects or products just beginning a production run. In this talk (a recording from the 2023 Teardown Conference), you’ll learn how to put a microcontroller or other custom circuit on a PCB a little larger than a stick of gum for less than $3 a board.
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.
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.
VolksEEG Project: Initial Hardware Architecture
The VolksEEG prototype pairs an Adafruit Feather nRF52840 Sense MCU with an ADS1299 analog front end, organized into non-isolated and isolated domains to protect patients. The post explains why isolation is required, which chips bridge the domains, and why simple, high-level power and signal diagrams help clarify the KiCad schematics for engineers and reviewers.
Introducing The VolksEEG Project
VolksEEG is an open-source effort to build an FDA-cleared clinical EEG and publish every design so others can manufacture it. The volunteer-driven project centers on the TI ADS1299 8-channel, 24-bit biopotential ADC and combines medical and electrical engineering expertise to confront regulatory, safety, and usability challenges. This blog series will document technical decisions, isolation and safety concerns, and ways engineers can contribute.
Levitating Globe Teardown, Part 2
Tim Wescott opens up a budget levitating globe and shows why it seems magical: a massive 30 mm rare-earth magnet and a deliberately cheap magnetic circuit. He documents a bolt used as the flux core, a likely microcontroller and hall sensor in the head, very fine winding in the electromagnet, and a single-transistor unidirectional drive. Part 3 will measure forces and sensor voltages to build a better controller.
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.
Tolerance Analysis
Jason Sachs walks through practical tolerance analysis by designing a 24V overvoltage detector from the ground up, combining resistor tolerances, temperature coefficients, reference and comparator errors, hysteresis, and dynamic RC behavior. He demonstrates worst-case stacking with real datasheet numbers, shows how solder and mechanical stress affect resistor choice, and sizes filtering so the comparator meets a microsecond-range trip requirement. The article is a hands-on guide full of worked examples and trade-offs for embedded hardware engineers.
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.
Modeling Gate Drive Diodes
This is a short article about how to analyze the diode in some gate drive circuits when figuring out turn-off characteristics --- specifically, determining the relationship between gate drive current and gate voltage during turn-off of a power transistor.
Lost Secrets of the H-Bridge, Part II: Ripple Current in the DC Link Capacitor
DC link capacitor ripple often determines capacitor life, yet the H-bridge waveform has a lot more structure than you might expect. Jason Sachs separates capacitor current into ramp and pulse components, derives closed-form peak and RMS expressions for edge and center PWM, and shows harmonic amplitudes. The post includes Python simulation so you can visualize the waveforms and apply the formulas to capacitor selection and EMI analysis.
Arduino robotics #3 - wiring, coding and a test run
Lonnie Honeycutt walks through wiring, coding, and the first test run of Clusterbot, a budget Arduino robot build costing about $50. The post provides a clear pin-mapping to the TB6612FNG motor driver, ready-to-upload Arduino movement functions, and practical tips like tinning thin battery wires. You also get PWM calibration values and the measured RPM timing the author used to make reliable turns.
7 Essential Steps for Reducing Power Consumption in Embedded Devices
Reducing the amount of power your embedded device is consuming is not trivial. With so many devices moving to battery operations today, maximizing battery life can be the difference between a happy, raving customer and an unhappy one that ruins your company's reputation. This post explores seven steps for optimizing your embedded systems' power consumption. You'll gain insights into the steps and techniques necessary along with receiving a few resources to help you on your journey.
Lost Secrets of the H-Bridge, Part I: Ripple Current in Inductive Loads
Jason Sachs digs into what PWM switching actually does to current in an H-bridge with an inductive load, and why that ripple matters for motors and power converters. He derives closed-form ripple formulas, shows how to compute a reference current I_R0 = VDC·T/L, and uses Python and sympy to plot and verify results. Read it for practical rules to halve ripple and raise its frequency.
Arduino robotics #1 - motor control
Clusterbot is Lonnie Honeycutt's first autonomous robot, built on a tight budget to teach practical motor control. This post explains why you cannot drive motors directly from an Arduino, how to wire and enable the Toshiba TB6612FNG motor driver, and offers hands-on PWM and calibration tips for getting smooth motion from cheap Mabuchi FA-130 toy motors.
R1C1R2C2: The Two-Pole Passive RC Filter
Jason Sachs walks through the math and simulation for the common two-pole passive RC filter, turning repetitive algebra into a compact reference you can reuse. He derives the closed-form transfer function, extracts the natural frequency and damping ratio, and explains why the topology cannot be underdamped without inductors or active stages. The post finishes with a state-space simulation recipe and practical component guidance.
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.
Tolerance Analysis
Jason Sachs walks through practical tolerance analysis by designing a 24V overvoltage detector from the ground up, combining resistor tolerances, temperature coefficients, reference and comparator errors, hysteresis, and dynamic RC behavior. He demonstrates worst-case stacking with real datasheet numbers, shows how solder and mechanical stress affect resistor choice, and sizes filtering so the comparator meets a microsecond-range trip requirement. The article is a hands-on guide full of worked examples and trade-offs for embedded hardware engineers.
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.
Lost Secrets of the H-Bridge, Part I: Ripple Current in Inductive Loads
Jason Sachs digs into what PWM switching actually does to current in an H-bridge with an inductive load, and why that ripple matters for motors and power converters. He derives closed-form ripple formulas, shows how to compute a reference current I_R0 = VDC·T/L, and uses Python and sympy to plot and verify results. Read it for practical rules to halve ripple and raise its frequency.
Lost Secrets of the H-Bridge, Part III: Practical Issues of Inductor and Capacitor Ripple Current
Jason Sachs cuts through the math to show what ripple current actually does to H-bridge hardware. He explains why peak current is the limiting factor for inductors, why capacitor ESR usually dominates DC-link voltage ripple, and how center-aligned PWM and duty selection reduce harmonics and ripple. Read this if you want practical rules of thumb and calculation templates for real power-electronics designs.
The Least Interesting Circuit in the World
Jason Sachs pulls apart the humble power-on reset and shows why the common RC-and-Schmitt trick is the least interesting but most dangerous circuit in your design. He walks through voltage thresholds, brown-out reset behavior, and how slow or noisy Vdd ramps can let parts start in indeterminate states. Read this for practical rules on choosing supervisors, comparators, and reset pulse timing to ensure reliable embedded startup.
Two Capacitors Are Better Than One
Jason Sachs revisits a simple stacked RC trick that dramatically reduces DC error from capacitor insulation leakage in long time-constant filters. Splitting one RC into two stages forces most of the DC drop onto the lower capacitor, squaring the remaining error while changing the effective pole locations. The post walks through the math, practical component tradeoffs, and when to prefer a digital approach.
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.
Byte and Switch (Part 2)
Running a thermistor front end from a single AA cell exposes problems you might not expect. Jason Sachs walks through a switchable-gain divider using a P-channel MOSFET and shows how MOSFET off-state leakage and low supply voltages can corrupt high-impedance temperature readings. The post compares bipolar transistors and analog switch ICs as fixes and gives practical component guidance for one-cell designs.
