Wake sources
Sleep in power-down until something worth waking for: the watchdog on a timer, or a pin change from a button. Which interrupt woke it, and the race you must close before sleeping.
Open it in the simulatorAll paths
Low power products
Make a battery last years: where an Uno’s current goes, sleep modes and wake sources, a power budget on a bare chip, measuring with a meter and an INA219, battery life checked against a draining cell, and a coin cell node.
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What you will build
2 projects, built step by step
7 lessons in 4 chapters, about 6 hours on a simulated Arduino Uno R3. Free, in your browser, every step checked by the simulator.
Measuring with the INA219
An INA219 in the node’s supply, read by an Uno over I2C: it catches the 10.4 mA wake the meter averages away, cannot see 7 uA of sleep, and the meter in series covers that.
Open it in the simulatorThe map
Chapter by chapter
Each lesson opens when the one before it is done, and each chapter ends in a project.
Chapter 1
Where the current goes
A meter in series, and what an Uno draws asleep and awake.
- Open270 XP
Where the current goes
An Uno on a 9 V battery with a meter in series on VIN: 44.9 mA running, what the board takes and what the chip takes, what an LED costs, and what delay() saves.
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- Locked350 XP
Sleep modes
Running, idle and power-down on the same Uno, read on the meter: what each sleep mode switches off, what wakes it, and why millis() stands still in power-down.
0 of 6 steps
- ProjectLocked700 XP
Wake sources
Sleep in power-down until something worth waking for: the watchdog on a timer, or a pin change from a button. Which interrupt woke it, and the race you must close before sleeping.
0 of 6 steps
Chapter 2
The bare chip
Microamps, a power budget, and the tools that measure it.
- Locked350 XP
A power budget
A bare ATmega328P on three AA cells wakes once a second, works and sleeps: microamps asleep on the meter, why the meter cannot catch a short wake, and a budget that turns a duty cycle into days.
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- ProjectLocked600 XP
Measuring with the INA219
An INA219 in the node’s supply, read by an Uno over I2C: it catches the 10.4 mA wake the meter averages away, cannot see 7 uA of sleep, and the meter in series covers that.
0 of 5 steps
Chapter 3
Batteries
Predict a battery’s life, then watch it drain.
- Locked300 XP
Battery life math
Predict how long a battery lasts, then watch it drain: an Uno counts the charge through an INA219, checks the prediction, and finds out why the battery outlives the simple sum.
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Chapter 4
Boss project
A coin cell sensor node that sleeps for years.
- Locked350 XP
Boss: a coin cell sensor node
An 8 MHz ATmega328P on one CR2032 wakes on the watchdog, powers its sensor from a pin, reads it, reports and sleeps, and works out from its own wake time how many days the cell will last.
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Syllabus
Every lesson in the course
All 7 lessons, in order, each with what it covers. Any of them opens in the editor right away.
Where the current goes
- Where the current goesAn Uno on a 9 V battery with a meter in series on VIN: 44.9 mA running, what the board takes and what the chip takes, what an LED costs, and what delay() saves.
- Sleep modesRunning, idle and power-down on the same Uno, read on the meter: what each sleep mode switches off, what wakes it, and why millis() stands still in power-down.
- Wake sourcesSleep in power-down until something worth waking for: the watchdog on a timer, or a pin change from a button. Which interrupt woke it, and the race you must close before sleeping.
The bare chip
- A power budgetA bare ATmega328P on three AA cells wakes once a second, works and sleeps: microamps asleep on the meter, why the meter cannot catch a short wake, and a budget that turns a duty cycle into days.
- Measuring with the INA219An INA219 in the node’s supply, read by an Uno over I2C: it catches the 10.4 mA wake the meter averages away, cannot see 7 uA of sleep, and the meter in series covers that.
Batteries
- Battery life mathPredict how long a battery lasts, then watch it drain: an Uno counts the charge through an INA219, checks the prediction, and finds out why the battery outlives the simple sum.
Boss project
- Boss: a coin cell sensor nodeAn 8 MHz ATmega328P on one CR2032 wakes on the watchdog, powers its sensor from a pin, reads it, reports and sleeps, and works out from its own wake time how many days the cell will last.
Keep going
The next course on your track
Low power products is part of the embedded track, a ladder of courses from zero to expert.
Firmware architecture
How a whole device is put together on the Uno: a scheduler and state machines, ISRs that only record, drivers behind interfaces, checked settings in EEPROM, error codes and the watchdog, safe updates, and a layered multi-sensor boss.
Open the next courseEmbedded track
Arduino, ESP32, Raspberry Pi Pico and STM32: pins, timing, buses, motors, WiFi, registers and debugging, every lesson checked on a simulated board.
See every course on the trackKits
Build it on your bench too
Every lesson runs in the simulator with nothing to buy. When you want the real thing, these kits have the parts.
Find your kit
Pick the starter kit you own and run every lesson in its manual with the same parts on the same pins.
See every kitQuestions
About Low power products
Is Low power products free?
Yes. All 7 lessons of Low power products are free and run in your browser, with nothing to install and no parts to buy before you start.
Do I need a real Arduino Uno R3?
No. Every lesson runs on a simulated Arduino Uno R3 with its parts on the canvas, and the simulator checks each step as you go. When you want to build it for real, the same wiring and code work on a real board.
How long does Low power products take?
About 6 hours: 7 lessons in 4 chapters, each one a few short steps. Your progress is kept, so you can stop after any lesson and pick up where you left off.
What will I build?
Each chapter ends in a project that puts it together: Wake sources and Measuring with the INA219.
Where do I start?
With "Where the current goes", and each lesson builds on the one before it. New to circuits? Electronics basics is the course that starts from zero.