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.
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.
Current and your body
Why current harms, and what the voltage classes mean.
| Lesson | Time | What students do |
|---|---|---|
| How a shock harmsYour 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 |
|
| Voltage classesMains, 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 |
|
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".
Fuses and lockout
What a fuse protects, and how to make a machine truly dead.
| Lesson | Time | What students do |
|---|---|---|
| Fuses protect the wireA 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 |
|
| Lockout and tagoutWhy 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 |
|
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".
Meters and batteries
Test before you touch, and keep lithium cells calm.
| Lesson | Time | What students do |
|---|---|---|
| Test before you touchOne 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 |
|
| Battery fireOne 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 |
|
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".
Boss project
Inspect a guarded press for every way it could hurt someone.
| Lesson | Time | What students do |
|---|---|---|
| Boss: a safety walk-throughWalk 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 |
|
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".
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.