House wiring simulator
Wire a house the way an electrician does, on a bench that can hurt no one: a main breaker and branch circuits, RCDs, switches and outlets, junction boxes, an energy meter, appliances with their real loads, and conductors sized by the codes, including the PDX cable and the practice used in the Philippines. Overload a circuit and the breaker trips; put a hand on a live wire and the RCD does, or does not, depending on how it was wired. Short circuits, lost neutrals and undersized cable all show up as what they are.
Open the labFree, in your browser, no account needed. Part of a free electronics simulator with 293 parts, 193 lessons and 66 builds.
What you can do
- Size a breaker and its conductor for a load, then prove it by overloading the circuit.
- See exactly what an RCD protects against, and the faults it cannot see.
- Plan a panel with the real loads of a Filipino home: aircon, rice cooker, water heater, lights.
- Check a solar inverter's grid connection and the switching between grid and battery.
Builds (11)
Light with one switch
One 9 W LED bulb on a 1-way wall switch, fed from a 10 A breaker.
Staircase light: two 3-way switches
A 15 W lamp switched from two places with a pair of 3-way (2-way in British terms) switches.
Fan and light on a 2-gang switch
A ceiling light (9 W) and a fan (40 W), each on its own rocker of one 2-gang switch.
Outlet circuit: three outlets on a 20 A breaker
Three duplex outlets on 3.5 mm² wire and a 20 A breaker, with a TV, refrigerator, rice cooker, kettle and flat iron…
House panel: main breaker and four branch circuits
A 60 A main, four branch breakers, two switched lights, an outlet with a TV and refrigerator, a 1 HP aircon and a 3.5…
RCD protection: someone touches a live wire
A water-heater circuit behind a 30 mA RCD, with a switch that lets a "person" (about 1 kΩ, hand to wet feet) touch the…
200 Ah power station from four 3.2 V prismatic LiFePO4 cells: 4S BMS, 2 × 12 V, 3 × USB, mains charger
12.8 V 200 Ah (2560 Wh) power station from four prismatic cells with a 4S BMS, two fused 12 V outputs, three USB…
200 Ah power station on a 12.8 V LiFePO4 battery: 2 × 12 V, 3 × USB, mains charger
12.8 V 200 Ah (2560 Wh) power station on a drop-in battery, two fused 12 V outputs, three USB outputs, a watt meter…
65 W USB-C PD charger from scratch: mains flyback (UC3844, 800 V MOSFET, PQ2625 transformer), TL431 + PC817 feedback, PD controller
65 W USB-C PD charger from parts: mains input filter, bridge and bulk, UC3844 flyback with RCD clamp and aux-powered…
Aircon branch circuit: 1.5 HP on 3.5 mm² and a 20 A breaker, on its own
Mains through a 20 A breaker and 3.5 mm² wire to a 1.5 HP non-inverter aircon on its own outlet. The tests share the…
Water heater circuit: 3.5 kW on 5.5 mm² and a 30 A breaker
Mains through a 30 A breaker and 5.5 mm² wire to a 3.5 kW storage water heater. The tests raise it to 5 kW and try the…
Lessons (23)
Basic transformer
Two windings on one iron core. The voltage scales with the turns ratio and the current scales inversely, so the power…
Three-phase star (Y)
Three loads share a common star point tied to neutral. Each sees the phase voltage, the line voltage between phases is…
Three-phase delta (Δ)
In a delta each load sits directly between two lines, so it sees the full line voltage. Each line current is the…
Using a multimeter
A voltmeter goes across a part (in parallel) and an ammeter goes in the loop (in series). Neither is perfect: the…
I²C sensor: accelerometer tilt
An accelerometer at rest measures gravity. How the 1 g splits across its x, y and z axes tells you how it is tilted…
Linear supply: transformer, bridge, capacitor, regulator
The four blocks of every mains supply before switch-mode: a transformer steps 220 V down and isolates it, a bridge…
Opto-isolated mains switching (zero-cross SSR)
A 5 V signal switches a 220 V lamp with no electrical connection between them. The MOC3063’s LED fires a…
Testing diodes and transistors with a meter
The meter’s diode range pushes about 1 mA through the part and shows the voltage across it. A good silicon junction…
Wiring, fuses and breakers for an array: the 1.25 and 1.56 rules
A PV conductor carries current for hours, and on an edge-of-cloud morning more than the datasheet’s Isc. So the…
12 V → 5 V regulators
Three ways to make 5 V from 12 V, each driving the same 10 Ω load. A linear 7805 burns the difference as heat, so its…
LM317 adjustable regulator
The LM317 keeps exactly 1.25 V between OUT and ADJ. R1 across that gap passes a fixed current, which also flows…
Heat inside a sealed box
Every watt dissipated inside a sealed enclosure has to leave through its walls, so the air inside warms up and every…
Series-pass regulator (transistor + Zener)
A Zener diode makes a steady reference, but it cannot supply much current. An emitter follower copies that reference…
Split supply: ± rails for op-amps
Two secondary windings in series with their junction as ground (a centre tap) feed one bridge: its + output is…
Buck converter from parts
A MOSFET chops 12 V on and off fifty thousand times a second; the inductor and capacitor average the chopped wave. The…
Boost converter from parts
Close the switch and the inductor stores energy from 5 V; open it and the inductor’s collapsing field adds its voltage…
SEPIC: output above and below the input
A Li-ion cell runs from 4.2 V full to 3.0 V empty, but the circuit wants 3.3 V the whole time. A SEPIC converter can…
LDO vs buck: choosing a 3.3 V rail
Two ways to make 3.3 V for a 100 mA load from 12 V. The AMS1117 linear regulator burns the difference as heat: its…
Charge-pump inverter: a negative rail
No inductor at all: a 555 square wave charges C1 through D1 while its output is high, then, when the output drops…
Reverse-polarity protection with a P-MOSFET
Connect a battery backwards and the electronics die. A diode in series protects but wastes about 0.9 V. A P-MOSFET…
Inrush limiting with an NTC
An empty 4700 µF capacitor looks like a short circuit at switch-on: the first current spike can blow fuses and weld…
Fault-finding a linear supply
Symptom: the 5 V supply hums and its output dips under load. Work from the output back to the mains: check the output…
Fault-finding a switch-mode output
Symptom: the 5 V buck converter is putting out nearly 11 V. A regulator that goes high has lost its feedback. Measure…
Parts (40)
DC adapter
Switching, regulated wall adapter · 12 V 1 A · centre-positive 5.5 × 2.1 mm
DC barrel plug (bare wires)
5.5 × 2.1 mm male barrel plug on a short lead · centre pin + (red) · sleeve − (black) · 5 A · lead…
Current source
Constant-current source · 10 mA · compliance 30 V
Three-phase supply
3-phase 4-wire · 230/400 V · 60 Hz · sequence L1-L2-L3 · 20 A per phase
Utility grid
Service drop · 220 V · 60 Hz
Variac
Variable autotransformer · 500 VA · in 220 V · out 125 V (0–250 V) · not isolated: the output…
Isolation transformer
Safety isolation transformer · 220 V : 220 V · 300 VA · the output floats: no path to earth…
Fuse
Blade fuse (ATO) in inline holder · 10 A · ATO/ATC blade · 32 V DC · 1000 A interrupting
Relay (SRD-12VDC)
SPDT power relay · 12 V coil (400 Ω, 400 mH) · contacts 10 A 250 V AC · pulls in at 70 %, drops…
Toggle switch
SPST bat-handle · OFF
Changeover switch
SPDT toggle · COM switched to A
Push button
12 mm tactile · momentary · hold to close
Wall switch
1-gang 1-way rocker · 250 V 10 A
AC breaker
2-pole MCB · C20 · 230/400 V~
RCD (30 mA)
2-pole residual-current device (RCCB) · 40 A · trips when 30 mA leaks to earth, within 40 ms ·…
DC breaker
2-pole MCB · C16 · DC 500 V, polarised
Resettable polyfuse
Resettable PTC fuse (polyfuse) · hold 0.5 A · Polymer PTC · 30 V · trips near 2× hold current…
Stop button (NC)
22 mm panel push button · normally closed · opens while pressed · red · 10 A
Contactor
3-pole contactor · 24 V DC coil · main contacts 9 A (AC-3, 4 kW motor) · auxiliary 13–14 normally…
Thermal flasher
Car turn-signal flasher (bimetal) · 12 V · 2 × 21 W lamps · lamp current heats a bimetal strip…
Solid-state relay (SSR-25DA)
Fotek-style SSR-25DA · input 3–32 V DC (about 7.5 mA) · output 24–380 V AC, 25 A with a heatsink ·…
Slide switch (SS12D00)
SS12D00 miniature slide switch · SPDT · 0.5 A 50 V DC · common on the middle pin · now to pin 1 ·…
Rotary encoder (KY-040) (EC11)
KY-040 incremental rotary encoder · 20 detents per turn, 1 quadrature cycle per detent · CLK/DT…
4×4 keypad
4×4 membrane keypad · 8 wires: rows R1–R4 and columns C1–C4 · pressing a key connects one row to…
Limit switch
KW11 lever microswitch · SPDT: COM, NO, NC · 5 A 250 V · snaps over when the lever is pushed: end…
Emergency stop
Emergency-stop push button · latching: pressing it locks the NC contact open until you twist to…
Fan speed switch
Piano-key speed selector · 250 V 5 A · key 3 pressed (3, high)
Bimetal thermostat (KSD301)
Snap-disc bimetal thermostat (KSD301 type) · 250 V 16 A · opens at 60 °C, closes again at 54 °C ·…
Thermal fuse
One-shot thermal fuse (SEFUSE type) · 250 V 10 A · opens for good at 95 °C · clip it to the part…
Hatch sealing loop
Sealing loop · 6 m of 3 mm stainless wire rope with a 40 AWG nichrome core (220 Ω/m, 1.32 kΩ) ·…
Surge protector (SPD)
PV DC SPD, Type 2, 600 V · DIN-rail module, two pluggable varistor cartridges with a status window…
Incandescent bulb
Miniature lamp · 6V 3W
12 V DC LED bulb
A60 E27 · 9 W · 12 V DC · either polarity
DC motor
130-size brushed · ~6 Ω
Active buzzer
Magnetic 12 mm · 3–12 V · ~2.3 kHz
220 V bulb
A60 E27 · LED 9 W · 220–240 V AC
220 V desk fan
12-inch desk fan · 40 W · 220 V AC
Household appliance
LED TV 43" · 100 W · 220 V AC
Speaker
Moving-coil loudspeaker · 8 Ω · 0.5 W · voice coil ≈ 0.2 mH
High-impedance earphone
Magnetic earpiece · 2 kΩ · sensitive enough to hear a crystal radio with no battery
Calculators
Ohm’s law calculator
Volts, amps, ohms and watts from any two
Wire size and voltage drop calculator
Voltage drop in a DC or single-phase run, and the size to use
Also on the lab
Solar PV simulator · Battery and BMS simulator · ESP32 simulator · Arduino simulator · Breadboard simulator · PCB layout and perfboard · Brownout backup · Piso Wi-Fi on solar · Questions answered · Compared with other simulators