Pat Hogan
Published © MIT

Cellular Connected Power Outlet

Usually, you might use WiFi to control your IoT projects at home, but what do you do when your WiFi is down?

IntermediateFull instructions provided4 hours5,670
Cellular Connected Power Outlet

Things used in this project

Hardware components

Hologram Global IoT SIM Card
Hologram Global IoT SIM Card
×1
Hologram Dash
Hologram Dash
×1
SparkFun Beefcake Relay Control Kit (Ver. 2.0)
×1
10A GFCI Power Outlet
×1
Dual Power Outlet Enclosure
×1
Dual Power Outlet Enclosure Cover
×1
Standard Power Strip
×1
2A USB Power Adapter
×1
Standard USB Cable
×1
Male/Female Jumper Wires
Male/Female Jumper Wires
×1
AMP Female Disconnects (12 - 10)
×1
Push-In Wire Connectors (3-Port)
×1

Software apps and online services

Hologram Data Router
Hologram Data Router
Arduino IDE
Arduino IDE

Hand tools and fabrication machines

Wire Stripper (Generic)
Soldering iron (generic)
Soldering iron (generic)
Screw Driver (phillips)
Precision Screw Driver Set
Cell Phone (SMS Compatible)

Story

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Code

Hologram Dash SMS Relay Control Code

Arduino
Upload this code to the Hologram Dash for it to control the connected power outlet.
The Dash will accept the following SMS messages:
ON (turns the power on)
OFF (turns the power off)
RESET (turns the power off for 30 seconds, then turns it back on)
int controlPin = R04;

// EFFECTS: Strips away the length number from the payload as it's not needed.
String stripOffLengthNumber(String payload) {

  int index = 0;
  while (payload[index] == ',') {
    ++index;
  }
  while (payload[index] != ',') {
    ++index;
  }
  ++index;

  payload.remove(0, index);

  return payload;
}


void setup()
{
  SerialUSB.begin(9600);
  Serial0.begin(9600); /* TTL UART */
  SerialCloud.begin(115200);
  pinMode(controlPin, OUTPUT);
  delay(4000);
  
  Dash.begin();
}

char currChar;
String tempBuffer = "";
String payload = "";
bool foundSMS = false;

void loop()
{

  while (Serial0.available()) {
    SerialCloud.write(Serial0.read());
  }

  while (SerialCloud.available()) {

    currChar = (char)SerialCloud.read();

    // check if the current buffer hits the SMSRCVD code.
    if (!foundSMS) {

      if (tempBuffer == "SMSRCVD") {
        foundSMS = true;
      }
    }
    // If it received the SMSRCVD code, the payload will get populated until
    // we get a \n.
    else if (currChar == '\n'){

      SerialUSB.println("\nSMS received: ");
      Serial0.println("\nSMS received: ");

      payload = stripOffLengthNumber(payload);

      SerialUSB.println(payload);
      Serial0.println(payload);

      if (payload[0] == 'O' && payload[1] == 'N') {
        digitalWrite(controlPin, LOW);
        SerialUSB.println("Switched to ON");
        Serial0.println("Switched to ON"); 
      } else if (payload[0] == 'O' && payload[1] == 'F' && payload[2] == 'F') {
        digitalWrite(controlPin, HIGH);
        SerialUSB.println("Switched to OFF");
        Serial0.println("Switched to OFF"); 
      } else if (payload[0] == 'R' && payload[1] == 'E' && payload[2] == 'S' && payload[3] == 'E' && payload[4] == 'T') {
        digitalWrite(controlPin, HIGH);
        SerialUSB.println("Resetting... Switched to OFF");
        Serial0.println("Resetting... Switched to OFF");
        delay(30000);
        digitalWrite(controlPin, LOW);
        SerialUSB.println("Switched to ON");
        Serial0.println("Switched to ON");
      }

      // reset foundSMS and the payload for the next iteration.
      foundSMS = false;
      payload = "";
    }
    else {
      payload.concat(currChar);
    }

    // Only keep a sliding buffer length of size 7
    // (need to only check for SMSRCVD).
    if (tempBuffer.length() >= 7) {
       tempBuffer.remove(0, 1);
    }

    // add latest char to our buffer.
    tempBuffer.concat(currChar); 

    SerialUSB.write(currChar);
    Serial0.write(currChar);
  }

  delay(5);
}

Credits

Pat Hogan

Pat Hogan

2 projects • 7 followers
Thanks to Nate.

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