Finished Dryer Will Text You

Here’s a slightly different way to check on the status of your laundry. Instead of checking if the machine is vibrating, or listening for sound, or pulling everything apart and hacking an ESP8266 into it, check the power that the machine is drawing. This is what [Scrand] did in his IoT dryer build.

The secret behind the hack is the Sonoff POW, a small device that sits in between the wall and the dryer. It has a relay in it that controls it, but, importantly for this hack, it’s able to measure the power consumption used by what’s plugged into it. By installing the ESPurna firmware on it, he can now use all the power of the firmware to control and monitor what’s connected to the POW. He wrote a PowerShell script to monitor the http server now running on the POW checking on how much power is being drawn by the dryer. When that power drops, the laundry is done, and in the case of [Scrand], a text is sent saying so.

When you’re sitting on the couch relaxing, why get up every five minutes to check your laundry when you can have it text you when you know it’s done? Then you can decide whether to get up and deal with it or just leave it until later. The whole reason ESPurna exists to begin with is to check on the status of the laundry.  Or, you can go a bit overboard with this laundry room monitor.

35 thoughts on “Finished Dryer Will Text You

    1. I was tempted to use a bit of string. Tempted to take it apart and add a couple of wires to the timer switch but an egg timer works seems to work well enough.
      Old fashioned non-eco driers are much better than the modern ones.
      For one they actually get hot within a minute or so instead of taking half an hour to get warm.
      I guess you could sense the current draw. Maybe even parasiticly power the device from a wire wrapped around the power cable and use the same loop to read the current.

      1. Unless you separated the conductors, wrapping a coil around the power cord will not return any useful signal because the currents in the two conductors cancel each other out and the result is 0.

    1. Not stock, no. But its easy to flash and doing a few calls for ntp and repeating timers would make this fairly straight forward to implement. I’m using both of these in different kind of project.

  1. Assuming, from the powerplugs, his dryer is running on 230V AC and pulls less than 10A (<2,3kW). This might be okay but I highly doubt that any similar dryer consumes so little power and the C13/C14 connectors are NOT rated for more than 10A / 70°C pin temperature and thus are a bad choice in this configuration!

    1. I just picked a random model that looks similar to the one in the photo, the BEKO WDX8543130W.

      It’s using Schuko plugs, so it’s presumably running at 220V.

      But energy consumption per cycle with dryer running for that model is 5.44 kWh.

      That’s around 24.73 max amps with the dryer heater on, depending on the power factor.

      Does the Sonoff POW support 25 amps? It only seems to support 3500 W and 16A.

      It is possible they are using a different model of course but drying clothes takes a fair bit of energy.

      1. The BEKO WDX8543130W is drawing 10A max (Or 2200W), see the manual. A complete cycle with washing and drying will take betwenn 2-5hours.
        25A would probably trigger / melt the fuse in your home

        1. If it uses “Total (Washing+Drying) Energy Consumption per cycle (kWh)” of 5.44 in total but it takes several hours to do so, it certainly could run and still remain under 16 amps the whole time. I was unable to quickly locate the total power draw but your link suggests it to be 2200 watts maximum. Which, under those voltage conditions should be around 10 amps after all.

    2. Some IEC 60320 Appliance couplers are for voltage not exceeding 250 V AC and rated current not exceeding 16 A.

      C13/14 connectors are only rated for 70 °C.

      Are you sure they are not using a different coupler? It’s still wrong anyway but would be slightly better than C13/14.

      1. schuko, lets say germany, thats more like 238V than 220 these days.
        11 amp, sure thats what you’d expect, but anything touched by an electrician in recent memory is 16.
        if you run your drier and washer in prallel, your socket might burn before the fuse trips…
        it’s fun, until u smell it. back to “fusing” not just the circuit but also each high output outlet… copper isn’t thaaat expensive.

        1. There are already several things about this that seem not quite right to begin with. They appear to have multiple potential issues and items that exceed capacity. Surprised that the Sonoff unit seems to readily cooperate though? Is it not internally fused or somehow protected from over current conditions?

  2. I did this for my washet with a Wemo Insight switch and some python code to keep an eye on it…when the power goes above a threshold it marks the cycle as started and then when it dips below it sends me a push message as well as a whole house audio message since the by buzzer is really quiet

    1. I like that one.
      Maybe add some feedback and turn it off when they are dry. Use the timer as a way to save your electricity bill. I’d also be tempted to add a similar thing with a smoke alarm myself too.
      Maybe a photo switch that tells you when the lint trap is full.

      1. If you’re talking about the primary trap, you should clean that before every load. Not cleaning it reduces the efficiency quite a bit, and increases the fire risk (although all the electric dryers I’ve ever seen have a high temperature limit switch on the heater coil assembly).

        My 1995 Whirlpool is a basic electro-mechanical dryer, but has a temperature sensor in the exhaust path that determines the dryness (“DRY-MISER”), and will turn off the heater elements once it thinks the load is dry enough.


    The software side is maybe a tad esoteric, but the main idea: current transformers -> ESP -> MQTT is a big winner.

    I’ve made a much nicer gizmo for the status notifier that shows when either washer/dryer is running, and when it’s done. The decentralization of pushing the data from the sensor nodes out to the MQTT system, and reading them from whatever else, makes it easy to decouple the design of the producer of the data and the consumer.

    Anyway… Go-go DIY IOT!

  4. Why not use a TH16 and monitor until humidity in the vent hose is ~constant. Your washing is now dry and can be switched off saving you money. And you get a notification too?

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