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Picture of ESP-8266 Smart Dishwasher (smart plug / smart socket)

We buy electricity from a local windfarm. Of course we are connected to the regular net with a steady supply of electricity. But I always wanted to adjust our consumption patern according to the available wind. Therefore I build a home system to monitor the availebility of windpower. The system monitors the national wind power, with forcasts for the next few days. The output is a chart of the forcasted wind power. This way we could manually switch devices. See my Instructable : WindPowerMonitor.

This new Instructable automates the process. I have build a wifi controlled socket to switch the dishwasher. Of course this wifi controlled socket can be used for any other purpose. And if you're the owner of solar panels, an addapted version of the underlaying program would be very usefull to switch some of your devices according to the availabilty of home produced solar power.

Why a dischwasher ?

  • it consumes quite a bit of electricity per cycle
  • it is often used (daily)
  • the task is most often not urgent and must only be done before a specific time (e.g. tomorrow before coming home from work)

Step 1: The hardware : Wifi controlled socket (ESP-8266)

Picture of The hardware : Wifi controlled socket (ESP-8266)
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First of all you'll need to build the wifi controlled power socket.

I have used the ESP-8266-12 as the controller and wifi connection. The ESP-8266 is very cheap. I bought 10 of them straigt from China for less than €50 ! And on top of that it is a real conroller, with 10 of so GPIO pins. No need of any other controller is needed. I used the "12" model because it has most of the GPIO pins broken out. With the "1" model the 2 available pins may never be pulled up at start-up, which sometimes can be in issue.

Bill of material :

  • ESP-8266-12 (any other model may do)
  • Relay 5V / 230v-10A
  • transistor BC547B + resistor
  • voltage regulator LM317 + resitor + resitor + condensator + condensator (to 3.3v for the ESP-8266)
  • optocoupler
  • voltage regulator 230v AC to 5v DC
  • socket + large enough box
  • wires 230v - 10A
  • wires 5v
  • sordering board
  • soldering equipment

How it works :

The high voltage circuit is switched by the relay.

The relay is switch by the ESP-8266. But to get there is a bit more complicated :

  • 230v-AC is transformed to 5v through the large voltage regulator.
  • Because the ESP runs best at 3.3V, the LM317 regulates a 3.3v circuit from the 5v ciruit. The output is connected to the ESP.
  • Pin 16 on the ESP give a digital signal (HIGH of LOW). But because the relay works on 5v, and can disturb the circuit on pulling high, the ESP and the relay are connected through an optocoupler.
  • The optocoupler I used did not give enough current. So to eventually switch the relay, a transistor was build in between.

The relay is connected in the 'normaly closed' position. So the socket is always ready to use. The switching programm actually first activates the relay and disconnects the socket. At the programmed time the switch is closed again.

The included image is not a working circuit but more a schematic how it basically works.

WATCH OUT : HIGH VOLTAGE ON THE CIRCUIT !