Electrical Engineering & PLC / Automation

A Kaern Schools applied course, taught on CyclePanel — the in-house browser-based PLC + HMI simulator from the cycleWASH / cycleCNC project family.

Who this is for. Career-changers, maintenance technicians, mechatronics apprentices, and self-taught makers who want to design, wire, program, and commission a real automated machine. No prior PLC experience is assumed; basic comfort with arithmetic and a willingness to think in terms of cause-and-effect logic is all you need.

What you'll be able to do by the end. Read and draw an industrial control schematic; size a fuse and pick a contactor; wire and scale a sensor; write structured PLC logic in Ladder and Structured Text; build an operator HMI; apply the safety standards that keep people alive; and commission a working machine from a cold panel to a running cycle. You will do all of this on a real-world reference machine: a cycleWASH bicycle-washing station — pumps, valves, a conveyor, sensors, an E-stop, and a touch HMI.

The tool — CyclePanel. CyclePanel is a browser-based simulator that mirrors a real PLC runtime. You wire a virtual panel, write IEC 61131-3 logic (Ladder/LD, Function Block/FBD, Structured Text/ST), bind it to an HMI canvas, and run it against a physics-lite model of the machine. Its vendor-migration pipeline lets you export the same project to Siemens (TIA / SCL), Codesys, and Allen-Bradley (Studio 5000) flavors — so what you learn here transfers to whatever brand your future employer runs. Everything runs in the browser; there is nothing to install and nothing to break that a "Reset machine" button won't fix.

Your tutor — Volt. Volt is your in-class instructor: a working automation engineer who has commissioned dozens of cleaning machines and who teaches the way a good mentor does — with analogies, war stories, and a question waiting at the end of every explanation. When you see Volt speaking, read it as if you're sitting in the front row.

Module 1 — Electrical Fundamentals

Learning objectives

• Explain voltage, current, resistance, and power, and apply Ohm's law and the power law to real loads.
• Distinguish DC control voltages (24 V DC) from AC supply (230/400 V) and explain why control panels use both.
• Read a load's nameplate and calculate its current draw.
• Describe series vs. parallel behaviour and why it matters for sensors and indicator lamps.
• Use a multimeter (simulated) to measure voltage, continuity, and current safely.

Lessons

Lesson 1.1 — Voltage, current, resistance: the water analogy that actually holds up

Teaching script (Volt):

"Alright, everyone settle in. Before we touch a single wire, I want you to picture a garden hose, because the water analogy is the one that genuinely survives contact with real machines. Voltage is the pressure pushing the water — measured in volts. Current is the flow rate, how much water actually moves per second — that's your amps. And resistance is the kink in the hose, anything that fights the flow — that's ohms. Now here's the relationship that pays your salary: Ohm's law. Voltage equals current times resistance, V = I × R. Crank the pressure up, more flows. Pinch the hose harder, less flows. That's the whole song. Why do you care? Because every device in our cycleWASH machine — every pump, every valve coil, every little sensor — is a 'load' with a resistance, and when you apply our 24-volt control pressure across it, a predictable current flows. If you know two of those three numbers, you always know the third. No guessing, no magic. A pump coil that reads 48 ohms on 24 volts will pull half an amp — and that number tells you what wire and what fuse you need. So tell me: if I put 24 volts across a solenoid valve and measure 0.5 amps flowing, what's the coil's resistance?"

Lesson 1.2 — Power, heat, and why things get hot

Teaching script (Volt):

"Here's a question that has burned more panels than I'd like to admit: where does the energy go? Power is the rate you're spending energy, measured in watts, and the formula is beautifully simple — power equals voltage times current, P = V × I. Our half-amp valve on 24 volts? That's 12 watts. Doesn't sound like much. But stack twelve of them in a tight cabinet on a summer day and suddenly you've got a little oven, and heat is the silent killer of electronics. Every resistor, every wire, every coil that isn't perfectly efficient turns some of your electrical energy into heat — that's the I-squared-R loss, and notice it grows with the square of current. Double the current, quadruple the heat. That's why we obsess over current. It's also why a thin wire carrying too much current glows and melts: it's a resistor you didn't mean to build. When we size the supply for the cycleWASH panel, we add up every load's watts, divide by voltage to get total amps, and then leave headroom — because a power supply run flat-out at 100% lives a short, unhappy life. So: our 24 V supply feeds loads totalling 96 watts. How many amps must it deliver, and would a 5-amp supply be enough?"

Lesson 1.3 — AC vs. DC, and why a panel needs both

Teaching script (Volt):

"Walk up to any real cycleWASH panel and you'll meet two completely different animals living in the same box. On the left, fat wires carrying 400-volt three-phase AC — that's the muscle, the stuff that spins the big wash pump motor. AC means the voltage swings back and forth fifty times a second; it's what the grid delivers and it's brilliant for motors and for shoving power over long distances. On the right, neat little wires at a calm, steady 24 volts DC — that's the nervous system. DC doesn't swing; it just sits at a constant level, which is exactly what logic circuits, sensors, and the PLC want. We bridge the two worlds with a power supply unit that rectifies AC down to clean 24 V DC. The golden rule that keeps you alive and keeps the machine sane: never mix the muscle and the nerves carelessly. High-voltage AC and low-voltage DC get separated, routed apart, and treated with very different respect. The PLC never switches 400 volts directly — it switches a little contactor coil on 24 V DC, and the contactor switches the big stuff. Think of the PLC as the conductor who never lifts a piano; he just points. Question for you: why do we use a low-voltage 24 V DC system for the control logic instead of just running everything on 400 V AC?"

Worked example

The cycleWASH rinse solenoid valve is rated 24 V DC, 6 W. We need its current draw to size wiring and fuse.

• Current: I = P / V = 6 W / 24 V = 0.25 A.
• Coil resistance: R = V / I = 24 / 0.25 = 96 Ω.
• In CyclePanel's Power Budget tool, this valve appears as a 0.25 A load on the 24 V rail. Add the inlet valve (0.25 A), two limit sensors (~0.02 A each), and the HMI (0.3 A): total ≈ 0.84 A, so a 2 A-rated 24 V supply is comfortable with headroom.

Hands-on exercise

In CyclePanel, open Sandbox → DC Bench. Place a 24 V supply, a switch, and a solenoid-valve load. Add the simulated multimeter. Measure the supply voltage, then close the switch and measure the current through the valve. Confirm your measured current matches P/V from the valve's nameplate. Now add a second identical valve in parallel and predict the total current before you measure it.

Common mistakes

1. Confusing parallel and series for current. Loads in parallel each draw their own current (currents add); students often expect the current to "split and stay the same."
2. Ignoring power-supply headroom. Sizing a supply to exactly the load total leaves nothing for inrush or aging; aim for ~25–50% margin.
3. Treating 24 V as "harmless so wiring doesn't matter." Low voltage still means real current and real heat in undersized wire.

Check for understanding

1. A motor nameplate reads 400 V, 1.5 kW. Roughly what current does it draw (single-phase approximation)? Why is the real three-phase answer lower?
2. Two 96 Ω valve coils are wired in parallel on 24 V. What is the total current?
3. Why does I²R loss make current — not voltage — the thing we watch for heat?