Easy Laundry Monitor

Get notified when your washer and dryer finish.

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A widget that sends an SMS when your washer and dryer finish running. Uses a Hall effect-based current sensor that is reliable and doesn't require modifying your appliances.

This is a widget which senses the current of your washer and dryer to let you know when they're done running.

This is different from similar projects in that it is reliable and doesn't require modifying your appliances. Typically, to measure current of an appliance, you'd need to split the cord so that you could attach a split-core current sensor. This is impractical and possibly dangerous. Instead, this project uses Hall-effect based current sensors.

This project supports notifying multiple people. It uses a button and an LED per person to toggle notifications.

Current sensors:

Buttons and LEDs (note: LED current-limiting resistors are inline):

Overall wiring:

Cable gland for USB cable/sensor leads:

View all 6 components

  • 1
    Prepare case

    Drill holes in your case for the LEDs and buttons (one each per person). Drill a hole for the USB cable and the sensor leads.

  • 2
    Solder buttons and LEDs

    Solder leads to your buttons and LEDs. My ESP32 board already had header pins soldered, so I attached Dupont cables to the buttons and LEDs so I could easily plug them in. My board only has two ground connections, so I soldered all of the button and LED grounds together.

    Don't forget current-limiting resistors for your LEDs. I soldered mine inline on the LED leds. I used 2.2k ohm resistors, so that the lights are visible but not too bright.

  • 3
    Test buttons and LEDs

    We're going to make sure the LEDs and buttons are working. Open up laundry-monitor.ino in the Arduino IDE. Comment out the body of send_message, so that it won't actually send an SMS. Copy constants.sample.h to constants.h, and fill out the people section with the phone numbers and pins that you'll use. Hook up the buttons and LEDs, and load the code. When you press the buttons, the LEDs should toggle.

View all 7 instructions

Enjoy this project?



Chuck Weiss wrote 05/15/2020 at 23:02 point

Unless I just can't find it somewhere, do you have a schematic of how you wired it all up?  I'd love to build this.

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Daniel wrote 05/11/2020 at 06:19 point

I once implemented a washing machine sensor in a similar way. But it was quite tricky to detect from the power consumption if the machine is still running. Depending on the mode, the machine may just do nothing for periods of ~10 mins during operation and therefore only draw the 'idle' power. As I didn't want to to add a long delay before the 'ready' signal is sent, I implemented some more complex filters. That works quite well, but I never got it 'perfect'.

Did you experience a similar issue?

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Adam Demuri wrote 05/12/2020 at 02:31 point

Yeah, I did run into that while tuning the filtering. My washing machine will use little or no power for periods while running. However, the current sensors I'm using appear to be pretty sensitive, so combined with some smart filtering, I don't have flakiness. Since tuning, I've been using this for a couple of months and haven't noticed any missed or extra notifications.

The algorithm I'm using is essentially a small median filter, then whenever that is non-zero, set a timer for several minutes. Once the timer expires, then the appliance is off.

  Are you sure? yes | no

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