Source: https://mokxi.com/teachers/plans/reading-electrical-drawings Updated: 2026-11-11 Lesson plan # Reading electrical drawings lesson plan Symbols, schematics, wiring diagrams, ladder diagrams, one-lines, floor plans and panel schedules, each read on the page and then proved on a circuit that runs. 6 chapters, 8 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 - The alphabet of a drawing, and what a node really is. - Where every wire lands, on a three-way switch. - Rails, rungs, contacts, coils and the seal-in. - A whole power system on one line, and switches on a plan. - What every breaker feeds, and how loaded each leg is. - Build a motor starter from its ladder drawing. ### Materials for the whole unit - Arduino Uno R3 - Bench power supply x 4 - Current sensor, ACS712 x 4 - DC motor - DPDT relay x 2 - Filament lamp - Full-size breadboard - Half breadboard x 4 - LED x 3 - Limit switch, lever microswitch - Multimeter - Pushbutton - Resistor x 9 - RGB LED x 4 - Slide switch x 4 - Transistor (NPN or PNP) x 2 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 10 min ## Symbols and schematics The alphabet of a drawing, and what a node really is. Lesson | Time | What students do Symbols: the alphabet of a drawing Read a first schematic symbol by symbol, a supply, a switch, a resistor, an LED and ground, then prove each one on the circuit it describes. | 35 min - Read it, then run it - A label is a promise - Switches are drawn at rest - Quiz: predict the current - Your symbol cheat sheet Nodes, dots and what a meter sees Three resistors and a meter: what a node is, why a dot means joined, and how to read the voltage a drawing predicts before you measure it. | 35 min - One node, one voltage - A dot means joined - Read the values, not the picture - Quiz: predict the reading - Drawings before parts ### Materials - Full-size breadboard - LED - Multimeter - Resistor x 3 - Slide switch ### Check for understanding Each student finishes "Nodes, dots and what a meter sees" on their own, without opening the hints. The simulator checks 5 of its 5 steps as they go. Then ask each one to explain, in a sentence or two, the last thing it asked of them: "Drawings before parts". Chapter 2. About 35 min ## Wiring diagrams Where every wire lands, on a three-way switch. Lesson | Time | What students do Wiring diagrams: where every wire lands A three-way switch drawn two ways: as a schematic that shows how it works and as a wiring diagram that shows which terminal every traveler lands on. | 35 min - Two switches, one light - Read the wiring diagram - Agree again from the far end - Quiz: predict the current - Where you will meet them ### Materials - Full-size breadboard - LED - Resistor - Slide switch x 2 ### Check for understanding Each student finishes "Wiring diagrams: where every wire lands" on their own, without opening the hints. The simulator checks 5 of its 5 steps as they go. Then ask each one to explain, in a sentence or two, the last thing it asked of them: "Where you will meet them". Chapter 3. About 40 min ## Ladder diagrams Rails, rungs, contacts, coils and the seal-in. Lesson | Time | What students do Ladder diagrams: rails and rungs The drawing every industrial electrician reads: two rails, rungs of contacts and coils, normally open and normally closed, and the seal-in that keeps a motor running. | 40 min - Rails and rungs - The seal-in - Normally closed STOP - The overload contact - Quiz: predict the rung - Ladders in the real world ### Materials - DC motor - DPDT relay - Full-size breadboard - Limit switch, lever microswitch - Pushbutton - Slide switch ### Check for understanding Each student finishes "Ladder diagrams: rails and rungs" 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: "Ladders in the real world". Chapter 4. About 1 h 15 min ## One-lines and floor plans A whole power system on one line, and switches on a plan. Lesson | Time | What students do One-line diagrams: a whole system on one line A generator transfer switch read from its one-line: two sources, two interlocked contactors and a load, then an outage and a transfer on a low-voltage model. | 40 min - One line for many wires - Follow the log - An outage - Transfer - Quiz: predict the lamp - Why one-lines matter Floor plans: a hallway with three switches Read the switch symbols on an electrical floor plan, S, S3 and S4, and prove a three-switch hallway on a logic model: any switch flips the light. | 35 min - Symbols on a plan - Any switch, any end - Through the middle - Quiz: predict the light - Reading a real plan ### Materials - Arduino Uno R3 - DPDT relay x 2 - Filament lamp - Full-size breadboard - Half breadboard - LED x 3 - Pushbutton - Resistor x 9 - Slide switch x 4 - Transistor (NPN or PNP) x 2 ### Check for understanding Each student finishes "Floor plans: a hallway with three switches" on their own, without opening the hints. The simulator checks 5 of its 5 steps as they go. Then ask each one to explain, in a sentence or two, the last thing it asked of them: "Reading a real plan". Chapter 5. About 40 min ## Panel schedules What every breaker feeds, and how loaded each leg is. Lesson | Time | What students do Panel schedules: what every breaker feeds Read a panel schedule, circuit numbers, breaker sizes, loads and legs, then watch a monitor flag a circuit over 80 percent, an overload and an unbalanced panel. | 40 min - The schedule - Demand against the main - The 80 percent line - Overload - Quiz: predict the balance - Keep the schedule true ### Materials - Arduino Uno R3 - Bench power supply x 4 - Current sensor, ACS712 x 4 - Full-size breadboard - Half breadboard x 4 - LED - Resistor x 9 - RGB LED x 4 ### Check for understanding Each student finishes "Panel schedules: what every breaker feeds" 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: "Keep the schedule true". Chapter 6. About 45 min ## Boss project Build a motor starter from its ladder drawing. Lesson | Time | What students do Boss: build it from the drawing The motor starter with three control wires missing. Read the ladder, draw each wire where the drawing says, prove the seal-in and the stop, then build revision B. | 45 min - STOP feeds START - The seal-in contact - OL to the coil - Test it: start and seal in - Test it: STOP - Revision B - Put it in your portfolio ### Materials - DC motor - DPDT relay - Full-size breadboard - Limit switch, lever microswitch - Pushbutton - Slide switch ### Check for understanding Each student finishes "Boss: build it from the drawing" on their own, without opening the hints. The simulator checks 7 of its 7 steps as they go. Then ask each one to explain, in a sentence or two, the last thing it asked of them: "Put it in your portfolio". Your class ## Teach this unit as a class Start a class from this course and its 8 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. From gates to a computer 23 lessons, about 16 h. Build a claw machine 8 lessons, about 6 h. 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