How to Reset Your Arduino from Code

In this video we talk about how to reset your Arduino from code with no hands. You can find the schematic and code from this video below.

***************Arduino Code from Video************************************

// Pin 13 has an LED connected on most Arduino boards.
int led = 13;
//create a variable for detecting what mode you are in. If used in interrupt must be "volatile"
/*volatile*/ bool nMode = 1;

void setup() {
  pinMode(4, OUTPUT); //set up pin 4, which is connected to base of transistor
  digitalWrite(4,LOW); //set to low so transistor is off and doesn't trigger reset
  pinMode(led, OUTPUT); //set up the LED pin to output
  Serial.begin(57600); //start serial comm
  Serial.println("We just started back up"); //print quick message so we know we just went through setup code
  Serial.println();
  Serial.end(); //need to shut off serial comm because it uses interrupts
  //Create interrupt: 0 for pin 2, the name of the interrupt function or ISR, and condition to trigger interrupt 
  attachInterrupt(0, interruptFunction, CHANGE); 
}

void loop() {
    digitalWrite(led, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(400);               // wait 
    digitalWrite(led, LOW);    // turn the LED off by making the voltage LOW
    delay(400);               // wait 
  /*
  noInterrupts(); //disables interrupts
  // critical, time-sensitive code here
  interrupts();//enables interrupts
  */
}

//This is the function called when the interrupt occurs (pin 2 goes high)
//this is often referred to as the interrupt service routine or ISR
//This cannot take any input arguments or return anything
void interruptFunction() {
  digitalWrite(4,HIGH); //with this variable set to 1 the LED will blink
 //detachInterrupt(0); this function call will turn the interrupt off
}

Utilizing the Arduino ADC Internal Reference

In this video we look at the ADC internal reference in an Arduino, why / when would you use it, how to ensure you get good measurement accuracy when using it, and how to use it to check your battery voltage.

**********************Arduino Code from the video****************************
float iREF = 1.08; //internal reference cal factor

void setup() {
  // put your setup code here, to run once:
  analogReference(EXTERNAL);
  //burn some ADC readings after reference change
  for(int i=0; i<8; i++) analogRead(A0);
  Serial.begin(57600);
}

void loop() {
  // put your main code here, to run repeatedly:
  delay(3000);
  Serial.print("Measured battery voltage is: ");
  Serial.println(fReadVcc());
  Serial.println();
}

//This function uses the known internal reference value of the 328p (~1.1V) to calculate the VCC value which comes from a battery
//This was leveraged from a great tutorial found at https://code.google.com/p/tinkerit/wiki/SecretVoltmeter?pageId=110412607001051797704
float fReadVcc() {
  ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
  delay(3); //delay for 3 milliseconds
  ADCSRA |= _BV(ADSC); // Start ADC conversion
  while (bit_is_set(ADCSRA,ADSC)); //wait until conversion is complete
  int result = ADCL; //get first half of result
  result |= ADCH<<8; //get rest of the result
  float batVolt = (iREF / result)*1024; //Use the known iRef to calculate battery voltage
  return batVolt;
}

Building a Wireless Sensor Network with the nRF24L01 Part 4

In part 4 of Building a Wireless Sensor Network with the nRF24L01 we take a look at the design's PCB layout in Eagle software as well as cover some software and hardware updates to the design.

You can access the updated code and PCB files from GitHub: https://github.com/ForceTronics/nRF24L01_Wireless_Sensor_Dev_Board

Building a Wireless Sensor Network with the nRF24L01 Part 3

In part three we take a look at the updated hardware schematic of the router / end device design, how the router / end device settings work, and we go over the initial software of the router / end device. You can find the code from this video in GitHub at https://github.com/ForceTronics/nRF24L01_Wireless_Sensor_Dev_Board

Building an AC Power Switch Development Board

Ever want to create a design that automates turning on or off an AC powered device such as a light or a heating system? Well this video is for you! In this video we look at how to create a development board for switching on and off AC power. The switch is implemented with a TRIAC which is a semiconductor device so no moving parts like a relay based design. You can access the Eagle PCB layout files from this link https://github.com/ForceTronics/AC-Switch-Proto-Board/tree/master or you can purchase this development board from www.forcetronics.com

Download Eagles files from GitHub: https://github.com/ForceTronics/AC-Switch-Proto-Board

*********************************Arduino code shown in the video********

//This sketch is used to control Thyristor that is used as a switch to turn on and off an AC line powered light. //This code is free for all to use

int8_t dig = 0; //default is high for light off

void setup() {

  //for controlling Thyristor

  pinMode(7, OUTPUT); //set pin to output so it can sink current from optoisolator

  digitalWrite(7, HIGH); //when high the thyristor is off or open

}

void loop() {

  delay(3000); //light turns on / off every 2 seconds

  togLight(); //call function to turn light on / off using digital pin

}

void togLight() {

  if(dig) { 

     digitalWrite(7, HIGH); //turn off light

     dig = 0; //toggle dig value

  }

  else {  

     digitalWrite(7, LOW); //turn light on

     dig = 1; 

   }

}

Building a Wireless Sensor Network with the nRF24L01 Part 2

In part 2 we focus on powering our wireless sensor node. We talk about batteries, battery sizing, estimating battery life, and battery monitoring. If you have any feedback or questions use the comments section below.

Updated Schematic for Part 2

Building a Wireless Sensor Network with the nRF24L01 Part 1

This is part 1 in a series where we look at how to build a large wireless network using Arduino and the nRF24L01+ Transceiver Modules. At the end of this series you will have a reference design for a wireless sensor development board and the code needed to turn the wireless sensor developments boards into a network. You will be able purchase all the hardware for this project at my site: www.forcetronics.com

Initial Hardware Design