Hello folks!
As a first project post I will show you the steps I take to develop a binary thermometer with a LM35 temperature sensor. It is a bit similar to this one from instructables, but mine is arduino-powered. My intention on this project was simply to test the power of arduino (UNO R3) on handling one of its ports (6 bits) at a time, and also the efficacy of the LM35 digital temperature sensor.
The prototype schematic
The schematic I created was drawn in Fritzing. My code (also available below) can be found in GitHub ( here). It is important to notice that the limits of temperatures that can be read are NOT the ones of the LM35, instead they are limited by the Arduino power supply voltage (0 +5V): so you are able to read temperatures between +2 and +150 degrees Celsius.
// Arduino timer CTC interrupt example (timer), from www.engblaze.com
// This example is a binary meter - shows a analog value in a binary (6-bit) output
// Modified by Clovis Fritzen, to fit as a binary thermomter (in may/2014)
// avr-libc library includes
#include < avr/io.h >
#include < avr/interrupt.h >
int sensorPin = A0; // select the input pin for the potentiometer
int sensorValue = 0; // variable to store the value coming from the sensor (LM35)
byte binaryValue= B00000000; // initialize port value as zeros
void setup()
{
DDRB = DDRB | B00111111; // set 6 pins in port B as outputs
// initialize Timer1
cli(); // disable global interrupts
TCCR1A = 0; // set entire TCCR1A register to 0
TCCR1B = 0; // same for TCCR1B
// set compare match register to desired timer count:
OCR1A = 15624; // for temperature
// turn on CTC mode:
TCCR1B |= (1 << WGM12);
// Set CS10 and CS12 bits for 1024 prescaler:
TCCR1B |= (1 << CS10);
TCCR1B |= (1 << CS12);
// enable timer compare interrupt:
TIMSK1 |= (1 << OCIE1A);
// enable global interrupts:
sei();
}
void loop()
{
// You would put another stuff program here
}
ISR(TIMER1_COMPA_vect)
{
// read the value from the sensor :
sensorValue = analogRead(sensorPin);
//digitalValue= sensorValue;
binaryValue= byte(sensorValue/2);
PORTB = binaryValue;
}
Some notes:
- The LM35 sensor is connected to the analog input A0;
- I put three colors of leds only to give an impression of "the warmer the color, the warmer the ambient (since the MSB is a red led, connected to pin 13 of arduino);
- I have only tested it indoors so far, and it showed to be accurate enough for a sensor like that, when compared to a DTH11 temperature sensor.
I hope you have liked it, and I promised I will try to put some videos of the actual circuits working, for the next experiments.
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