Solar powered ESP8266. WiFi module usage optimizations

Question

Above all, I am quite new to the ESP8266 and micro controllers development as a whole. I am now working on a project which is quite simple for now. It basically looks like this:

As you can see, I have an ESP8266 and some input peripheral. Everything works perfectly fine for the moment, I can read the inputs from the motion sensor and 4x3 keypad. And, respectively I can output on the relay and the 5mm LED. In order to make it a real IOT, I have connected it to the internet via Thinger.IO. So, I have my ESP8266 constantly connected to this platform and I can track it anytime, from anywhere.

This is great. But, my optimal goal is to power my configuration from a solar panel and make it independent of the electricity distribution network.

The average working current of the whole system is about 313mA (10000 mAh battery gets completely drained for 32 hours. Its output is 5V, 2.1A).

So, I am now in a search of the best solar panel to fit my needs. An ultimate one would have the following maximal dimensions: 30x35 cm. I am not sure there's a single panel that I can use but I am interested to hear your opinion in this.

Another aspect, that I'd like to optimize is the constant internet connectivity. Basically, I need to have my configuration connected to the internet only when keypad input was made or motion sensor detected something. During the rest of the time, I don't need to be connected to the internet and I assume WiFi module could be suspended somehow. Currently, my code uses SmartConfig and is looks like this:

#include <ESP8266WIFI.h>

void connectToWifi() {
  WiFi.mode(WIFI_STA);
  WiFi.beginSmartConfig();

  while(!WiFi.smartConfigDone()){
    delay(500);
  }
}

void setup() {
  connectToWifi();

}

void loop() {

}

Everything works well. But, as I said, I'd like to be able to start/stop the WiFi module. I tried using the following API:

void toggleWifi(bool isWakeUpCall) {
  if(isWakeUpCall)
    WiFi.forceSleepWake();
  else
    WiFi.forceSleepBegin(30000000);

  delay(500);
}

but without much of a success. Once it gets into this portion of code, it gets completely disconnected and doesn't get connected anymore. I am now struggling with it.

I've read about the sleep modes offered by the ESP8266 but I don't think they are suitable for my case because I can not simulate external interrupt (or maybe I can?).

I am really curious to hear your opinion on this. :)

Answer 1

As described here the ESP8266 can be waken up using Timer Wake Up or external interrupt. The idea is simple: almost everything inside the ESP is powered down (including Wi-Fi and/or System clock or even the CPU) with only a timer running which was told when to activate before the ESP went to sleep. After the desired amount of time has passed the timer triggers GPIO 16 or D0 and if that is connected to the reset pin of the ESP is resets and starts executing code again until it goes to sleep again. For your case you can configure your motion sensor to output a LOW when motion is detected and connect is to a GPIO pin and the reset pin, so it will trigger a restart when motion is detected and in the startup sequence you look at the pin where the sensor is connected and do what you have to do. For the keyboard to work you can have the timer set to reset every 5 seconds, so you would have to hold a button for 5 seconds waiting for the ESP to wake up and accept your input or you could make a dedicated button for waking up the ESP if you want to enter the code. In that case the you don't need a timer, since as you described the ESP only has to do anything if the keyboard is activated or if the motion sensor is triggered and since they can be connected as external interrupts they will wake up the ESP if needed. I would recommend to check out this link for further details about the code and hardware.