Key idea
I/O list
Devices
Hint
Test sequence
Start by tapping the flashing dashed line, then choose a device.
Control room
Timelinelast 30 s
Try it yourself
Start by tapping the flashing dashed line, then choose a device.
Johdota is a free browser game about relay control, motor circuits and PLC programming. It is made for electrical and automation apprentices and students, and for anyone who wants to brush up on control circuits. Every task is a written brief, like on site. On the relay side you wire the control circuit and, where needed, the motor power circuit. On the automation side you wire the inputs and outputs of a small PLC and write the program as a ladder diagram. The game tests whether your solution works.
There are 100 tasks in 20 sections: 10 on the relay side and 10 on the automation side. The first task of each section teaches the basic idea, and the ones after it get harder.
The circuit, NO and NC contacts, connecting in series and in parallel.
Push-button and light · Two-hand control · Control from two places · Rotary switches · Inhibit condition
The relay, self-holding, start priority and stop priority.
Relay controls a light · Run and stop lights · Self-holding · Start priority · Self-holding from two places
Interlocks, chains of conditions and sequential starting.
Interlock and condition · Self-holding with indicator lights · Sequential starting · Interlocking · Chain of three conveyors
Three-phase power circuit, local isolator, motor protection and inching.
Cabling a motor · Direct-on-line starting · Inching · Isolator feedback contact · Motor protection fault light
Phase swap, contactor interlock, limit switches and automatic back-and-forth movement.
Reversing power circuit · Complete reversing circuit · Direct reversing · Hoist with limit switches · Automatic back-and-forth
On-delay and off-delay, start-up warning, flashing light and star-delta starting.
Delayed start · Staircase timer · Start-up warning · Flashing alarm light · Star-delta starting
Sensors, level control, alarms, resets and the counter relay.
Twilight switch · Door alarm · Tank filling · Hand-Off-Auto · Counter relay
Impulse relay, heating, pump alternation, two-speed fan and standby pump.
Impulse relay · Electric heating · Pump alternation · Two-speed fan · Standby pump
Emergency stop, thermal overload relay and phase failure relay, safety relay, dry-run protection and standby power.
Emergency stop · Overload and phase failure relays · Safety relay · Dry-run protection · Standby power
Five complete systems that need everything you have learned.
Smoke vent · Garage door · Conveyor line · Booster pump · Mixer
Inputs and outputs, your first program, self-holding, set and reset, feedback contacts and interlocks.
First program · Self-holding in the program · Leak alarm · Motor protection to PLC · Reversing
Rising and falling edges, memory bits, acknowledging alarms and local/remote selection.
One button · Stuck button · Alarm acknowledgement · Corridor lights · Local and remote control
On-delay TON, off-delay TOF, pulse TP, flashing and limiting start frequency.
Wave filtering · Fan run-on · Electric lock · Flashing alarm · Start frequency
Counting up and down, counter reset, batches, service limits and sorting.
Item counting · Car park · Packing line · Service reminder · Sorting
One step at a time: transition conditions, pneumatic cylinders, timed steps and interrupting a sequence.
Filling and emptying · Pillar drill · Pedestrian crossing lights · Tank batch · Transfer unit
Scaling, hysteresis, broken wire detection, limit value alarms and staged control.
Scaling · Hysteresis · Broken wire · Limit value alarms · Two pumps in stages
Run and direction, speed reference from an analogue output, preset speeds, fault reset and speed controlled by pressure.
Run and direction · Speed reference · Preset speeds · Fault reset · Pressure-controlled speed
Feedback monitoring, emergency stop with a safety relay, run-time monitoring, power cuts and sensor plausibility.
Contactor monitoring · Emergency stop and safety relay · Jam monitoring · Power cut · Sensor plausibility
Weekly timer and twilight switch, day and night temperature, ventilation controlled by CO₂, pump alternation and alarm collection.
Outdoor lighting · Day and night temperature · CO₂-controlled ventilation · Pump alternation · Alarm collection
Wastewater pumping station, sorting line, storage lift, booster pumping station and a mixing process with recipes.
Wastewater pumping station · Sorting line · Storage lift · Booster pumping station · Mixing process
What does a contactor, a timer relay or a thermal overload relay do, and how is it wired? What about a small PLC or a variable speed drive? Every device in the game is explained in the device guide.
Johdota follows IEC standards. Pick your region from the top bar: wire colours and conductor names follow it (for example "active" in Australia and New Zealand). Terminal markings (13–14, A1–A2) follow IEC 60947 and are the same in all IEC countries. Device letters (K1, S1) follow common IEC practice, which can vary between countries and companies. Johdota was first written in Finnish, so if something does not match practice in your country, please tell us with the Feedback button.
All completed levels, wiring and settings are deleted, and the game starts again from the first level, as for a new player. Your region is kept.
Johdota is a game about relay control, motor circuits and PLC programming.
100 tasks with relays and PLCs, each a little harder than the last.
Johdota was first written in Finnish. If a term or symbol is different in your country, please tell us with the Feedback button.
Language: English · Suomeksi
Language: English · Suomeksi
Johdota was first written in Finnish. If a term, symbol, colour or standard does not match practice in your country, please tell us with the Feedback button. Every report helps.
All the wiring you have made for this level will be deleted.
live wire