Smartifying a washing machine

2026-02-15

This article extends the basics covered in Smartifying your devices to a device with a more complicated state: A washing machine. By using both a smart power plug and a contact sensor, we can track the activity of the machine, and the state of the door. For example, this helps us identify when a washing machine cycle has finished, but the load has not yet been emptied.

We'll build up the washing machine's state machine incrementally, based on specific triggers that we get from the smart devices.

The "washing machine" sensor shows what the washing machine is doing.
The contact sensor responds to the magnet attached to the door.
The contact sensor uses a magnet to sense when the door opens and closes.

In this article, we'll skip the imperative approach and go straight to the state machine examples. Continue scrolling to see the Node Red implementation.

Keep reading if...

  • You have access to advanced Smart Home tooling, like Home Assistant.
  • You're familiar with state machines, and modeling device state in Node Red
  • You keep forgetting to take the washing out when it's finished

Sensors and triggers

We will use a contact sensor and a smart power plug. Instead of imperatively mapping the smart home sensor events directly to actions, we will treat them as "triggers" to influence the device state.

In addition, we'll also take advantage of the device state itself to provide additional information - state duration helps us identify if a cycle has finished, and trigger reminders if a cycle has finished, but if the door has not been opened for a while since then.

We'll start with the contact sensor.

Contact sensor: Is the door open?

The door sensor let us estimate when a load is added or removed. We won't know if the washing machine is empty or full, but we can cross-reference this with other sensors soon.

Contact sensors give us isOpen and isClosed triggers.
 
 We can use these triggers to start modeling the door state. 
 
 
Smart power plug: Is it washing?
 

    While it may be possible to identify specific cycle information by monitoring the power usage,
    we only need to identify when the washing machine is running a cycle, or when it isn't.
  
 
 
Categorising power usage gives us powerHigh,
        powerLow and powerOff triggers.
      
 
 
 
We assume that the door can't be open while the washing machine is washing.
 
 

    While it's possible to model the "Power off & door open" and "Power off & door closed" as
    separate states, the added complexity does not benefit us because the transitions are
    the same. Ideally we would model them as a substates in a hierarchical finite state
    machine, so the information is still available in the model without additional overhead.
  
 
Timing transitions: Did the cycle finish?
 

    We're still missing something critical from these triggers; the ability to identify when the
    washing machine has finished a cycle. Cross-referencing the
    powerLow trigger with the washing state
    duration, we can decide which next transition is most appropriate:
  
 
 
  • 
      If powerLow triggers soon after starting a cycle (e.g. pausing it
      to add more clothes), consider the cycle cancelled.
    
    •  
  • 
      If powerLow triggers after the cycle has been running for 30 mins
      or more, consider the cycle finished.
    
 

    This expands our model further, to represent "finished" as new state, distinct from "ready".
  
 
 

    "Finished" represents a washing machine that has finished a cycle, and is full of clean clothes.
    We assume the clothes are removed when the door is opened.
  
 
modeling the state machine
 

    Because we're using a simple state machine instead of a  hierarchical state
    machine, the states and transitions look a little more complicated than we saw in the diagrams
    above.
  
 

    Since this state machine is just a rough model of a physical process using simple sensors, there
    are cases where transitions may be missed. We can add safe defaults for some triggers, allowing
    transitions without regard for the "from" state.
  
 
Trigger From To Comment
 
doorOpened readyOff doorOpenedOff Door opened while the washing machine is turned off.
 
(any) doorOpenedOn Door opened while the washing machine is in any other state.
 
doorClosed doorOpenedOff readyOff Door closed while the washing machine is turned off.
 
(any) readyOn Door closed while the washing machine is in any other state.
 
powerHigh (any) washing 
              The washing machine is running a cycle. Implies that it's on and the door is closed.
            
 
powerLowLongTime washing finished 
              The only way to transition to "finished", low power after washing for > 30 mins.
            
 
powerLowShortTime washing ready Low power after washing for < 30 mins.
 
powerOff doorOpenOn doorOpenOff Substate for doorOpen, when the power is turned off.
 
finishedOn finishedOff Substate for finished, when the power is turned off.
 
(any) readyOff Safe default for other states when the power is turned off.
 
powerOn doorOpenOff doorOpenOn Substate for doorOpen, when the power is turned on.
 
finishedOff finishedOn Substate for finished, when the power is turned on.
 
(any) readyOn Safe default for other states when the power is turned on.
 
Putting it all into Node Red
 

    As with  Smartifying your devices, we're representing the
    device state using the
    node-red-contrib-home-assistant-websocket
    and
    node-red-contrib-persistent-fsm, nodes, which do not render properly in this preview.
  
 
 
Reminders
 

    Further taking advantage of the state duration, we can add additional state nodes that fire when
    the washing machine has been in the finished state for a certain
    duration. The "announcement" node delegates to a TTS to verbalise messages and play them as
    announcements.
  
 
 
Which reminds me to stop what I'm doing and put the washing out:
 
  1. 🤖 Smart Home agent
    2.  
    3.  
  3. ...🙄
 
Wrapping up
 

    Smartifying a washing machine with multiple sensors led to a more complicated state machine than
    the example in  Smartifying your devices, but it's good to
    prove that the process can scale. I'll be keeping an eye out for other
    Smart Home sensors and actuators at IKEA
    that can further smartify my devices.
  
 

    If you have feedback or questions about this article, let's catch up via
      email.