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.
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.
Symbols and schematics
The alphabet of a drawing, and what a node really is.
| Lesson | Time | What students do |
|---|---|---|
| Symbols: the alphabet of a drawingRead 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 |
|
| Nodes, dots and what a meter seesThree 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 |
|
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".
Wiring diagrams
Where every wire lands, on a three-way switch.
| Lesson | Time | What students do |
|---|---|---|
| Wiring diagrams: where every wire landsA 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 |
|
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".
Ladder diagrams
Rails, rungs, contacts, coils and the seal-in.
| Lesson | Time | What students do |
|---|---|---|
| Ladder diagrams: rails and rungsThe 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 |
|
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".
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 lineA 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 |
|
| Floor plans: a hallway with three switchesRead 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 |
|
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".
Panel schedules
What every breaker feeds, and how loaded each leg is.
| Lesson | Time | What students do |
|---|---|---|
| Panel schedules: what every breaker feedsRead 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 |
|
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".
Boss project
Build a motor starter from its ladder drawing.
| Lesson | Time | What students do |
|---|---|---|
| Boss: build it from the drawingThe 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 |
|
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".
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.