Source: https://mokxi.com/teachers/plans/electrical-safety Updated: 2026-11-12 Lesson plan # Electrical safety for every bench lesson plan How shock harms, voltage classes, fuses, lockout and tagout, testing before you touch and battery fire, on low-voltage stand-ins you can break safely, then a guarded press to inspect. 4 chapters, 7 lessons, about 5 hours, no board. Every lesson runs in the browser, with nothing to install. Start a class from this course The unit ## Objectives and materials ### By the end, students can - Why current harms, and what the voltage classes mean. - What a fuse protects, and how to make a machine truly dead. - Test before you touch, and keep lithium cells calm. - Inspect a guarded press for every way it could hurt someone. ### Materials for the whole unit - Arcade button x 2 - Arduino Uno R3 - Battery: AA, coin cell, LiPo - Bench power supply - Buzzer - Capacitor - Character LCD with I2C backpack - DC motor - Diode x 2 - Filament lamp x 3 - Full-size breadboard - Half breadboard - Hobby servo - IR proximity switch, E18-D80NK x 2 - Limit switch, lever microswitch - Mains transformer, 230 V or 120 V to 12 V - Multimeter - Oscilloscope - Resistor x 3 - Signal generator - Slide switch x 2 - Traffic light module Every part is already on the simulator’s bench, so there is nothing to buy or hand out. The counts are the most any one lesson uses, if you build it on real breadboards too. Chapter 1. About 1 h 20 min ## Current and your body Why current harms, and what the voltage classes mean. Lesson | Time | What students do How a shock harms Your body as a resistor on the bench supply: why current, not voltage, does the harm, how wet skin changes everything, and why mains is never a bench experiment. | 35 min - Your body is a resistor - Dry skin - Wet hands - Quiz: predict it first - Where it flows, and why mains is different Voltage classes Mains, safely on a screen: a 230 V signal through a transformer to a low-voltage supply, what extra-low voltage means, the US 120 V version, and what the wrong transformer does. | 45 min - Mains on a screen - The transformer is the wall - The classes - The US version - Quiz: the wrong transformer - The danger side ### Materials - Bench power supply - Capacitor - Diode x 2 - Full-size breadboard - Half breadboard - Mains transformer, 230 V or 120 V to 12 V - Multimeter - Oscilloscope - Resistor - Signal generator ### Check for understanding Each student finishes "Voltage classes" on their own, without opening the hints. The simulator checks 6 of its 6 steps as they go. Then ask each one to explain, in a sentence or two, the last thing it asked of them: "The danger side". Chapter 2. About 1 h 20 min ## Fuses and lockout What a fuse protects, and how to make a machine truly dead. Lesson | Time | What students do Fuses protect the wire A small lamp plays a fuse: loads add current, a fault makes the fuse go white hot while the lamps go dark, a current limit trips instead, and why a fuse is sized to the wire, not the gadget. | 35 min - One lamp on - Add a load - Quiz: the fault - A limit that trips instead - Size it to the wire Lockout and tagout Why a STOP button is not off: a disconnect that really isolates, a capacitor that keeps the line live after it opens, bleeding the stored energy, and the lockout steps in general terms. | 45 min - A machine running - STOP is not off - Open the disconnect - Bleed the stored energy - Quiz: no bleeder - The lockout steps ### Materials - Bench power supply - Capacitor - DC motor - Filament lamp x 3 - Limit switch, lever microswitch - Multimeter - Resistor - Slide switch x 2 ### Check for understanding Each student finishes "Lockout and tagout" on their own, without opening the hints. The simulator checks 6 of its 6 steps as they go. Then ask each one to explain, in a sentence or two, the last thing it asked of them: "The lockout steps". Chapter 3. About 1 h 30 min ## Meters and batteries Test before you touch, and keep lithium cells calm. Lesson | Time | What students do Test before you touch One meter on a divider: a live reading, proving a circuit dead, why ohms lies on a live circuit, what the meter categories mean, and the live-dead-live habit. | 45 min - A live reading - Prove it dead - Ohms lies on a live circuit - Ohms with the power off - Quiz: predict the tap - Meter categories Battery fire One 18650 lithium cell on a dead short: over 20 A, the heat inside the cell, a smaller fault, storage charge, and what to do when a cell goes wrong. | 45 min - A full cell - Short it - Heat inside the cell - Quiz: a smaller fault - Storage charge - Battery rules ### Materials - Battery: AA, coin cell, LiPo - Full-size breadboard - Multimeter - Resistor x 3 - Slide switch ### Check for understanding Each student finishes "Battery fire" on their own, without opening the hints. The simulator checks 6 of its 6 steps as they go. Then ask each one to explain, in a sentence or two, the last thing it asked of them: "Battery rules". Chapter 4. About 55 min ## Boss project Inspect a guarded press for every way it could hurt someone. Lesson | Time | What students do Boss: a safety walk-through Walk a guarded press like a safety inspector: a safe stroke, a refused start, a hand through the light curtain, a reset that waits, a wider guard you set yourself, and the e-stop. | 55 min - Meet the press - One safe stroke - A start it refuses - A hand in the press - Quiz: reset with the beam blocked - Make it yours: a wider guard - The e-stop - Your walk-through ### Materials - Arcade button x 2 - Arduino Uno R3 - Buzzer - Character LCD with I2C backpack - Half breadboard - Hobby servo - IR proximity switch, E18-D80NK x 2 - Slide switch - Traffic light module ### Check for understanding Each student finishes "Boss: a safety walk-through" on their own, without opening the hints. The simulator checks 8 of its 8 steps as they go. Then ask each one to explain, in a sentence or two, the last thing it asked of them: "Your walk-through". Your class ## Teach this unit as a class Start a class from this course and its 7 lessons are assigned in one go, in order. Students join with a six-character code or printed login cards, and each one’s work comes back to you. The class tools are free for 30 days for one class of up to 20 students, with no card. The lessons themselves are free either way. Start a class from this course See the demo class More units ## Other lesson plans Electronics basics 20 lessons, about 10 h. Embedded on the Arduino Uno 16 lessons, about 12 h. Embedded on the ESP32-C3 13 lessons, about 11 h. Embedded on the Raspberry Pi Pico 7 lessons, about 6 h. Build your own fight stick 5 lessons, about 4 h. Embedded on the STM32F411 6 lessons, about 6 h. C++ on a board 13 lessons, about 10 h. Digital logic and memory 4 lessons, about 4 h. Interactive devices on the Uno 9 lessons, about 8 h. 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