/* IO Expander
*
* Basement/Crawlspace Ventilation System v1.1
*
*/
#include <math.h>
#include <SoftwareSerial.h>
#include <avr/wdt.h>
#include "IOExpander.h"
#define FAHRENHEIT
#define ONEWIRE_TO_I2C_ROM "i4s71"
#define INIT_OLED "st13;si;sc;sd"
#define HUMIDITY_SENSOR_INSIDE "s6t1"
#define HUMIDITY_SENSOR_OUTSIDE "s8t1"
#define FAN_ON "r1o"
#define FAN_OFF "r1f"
#define ABSOLUTE_DELTA_FAN_ON 1 // Fan on if absolute humidity delta of inside >= outside
#define ABSOLUTE_DELTA_FAN_OFF 0.5 // Fan off if absolute humidity delta of inside <= outside
#define OUTSIDE_RELATIVE_FAN_ON 88 // Fan on if outside relative humidity is <= %
#define OUTSIDE_RELATIVE_FAN_OFF 90 // Fan off if outside relative humidity is >= %
#define MINIMUM_TEMPERATURE 15 // Cycle vent on/off if outside temperature <= 15C/59F
#define FAN_ON_TIME (20*60*1000L) // 20 min
#define FAN_OFF_TIME (20*60*1000L) // 20 min
//#define SERIAL_DEBUG
#define SERIAL_TIMEOUT 5000 // 5 sec delay between DHT22 reads
#ifdef SERIAL_DEBUG
SoftwareSerial swSerial(8,7);
#endif
struct HS {
float temp;
float relative;
float absolute;
bool error;
};
int led = 13;
bool init_oled = true;
long ontime, offtime;
#ifdef FAHRENHEIT
#define C2F(temp) CelsiusToFahrenheit(temp)
float CelsiusToFahrenheit(float celsius)
{
return ((celsius*9)/5)+32;
}
#else
#define C2F(temp) (temp)
#endif
void SerialPrint(const char* str, float decimal, char error)
{
Serial.print(str);
if (error) Serial.print(F("NA"));
else Serial.print(decimal, 1);
}
float DewPoint(float temp, float humidity)
{
float t = (17.625 * temp) / (243.04 + temp);
float l = log(humidity/100);
float b = l + t;
// Use the August-Roche-Magnus approximation
return (243.04*b)/(17.625-b);
}
#define MOLAR_MASS_OF_WATER 18.01534
#define UNIVERSAL_GAS_CONSTANT 8.21447215
float AbsoluteHumidity(float temp, float relative)
{
//taken from https://carnotcycle.wordpress.com/2012/08/04/how-to-convert-relative-humidity-to-absolute-humidity/
//precision is about 0.1°C in range -30 to 35°C
//August-Roche-Magnus 6.1094 exp(17.625 x T)/(T + 243.04)
//Buck (1981) 6.1121 exp(17.502 x T)/(T + 240.97)
//reference https://www.eas.ualberta.ca/jdwilson/EAS372_13/Vomel_CIRES_satvpformulae.html // Use Buck (1981)
return (6.1121 * pow(2.718281828, (17.67 * temp) / (temp + 243.5)) * relative * MOLAR_MASS_OF_WATER) / ((273.15 + temp) * UNIVERSAL_GAS_CONSTANT);
}
void ReadHumiditySensor(HS* hs)
{
SerialCmd("sr");
if (SerialReadFloat(&hs->temp) &&
SerialReadFloat(&hs->relative)) {
//hs->dewpoint = DewPoint(hs->temp, hs->relative);
hs->absolute = AbsoluteHumidity(hs->temp, hs->relative);
hs->error = false;
}
else hs->error = true;
SerialReadUntilDone();
}
void setup() {
Serial.begin(115200);
#ifdef SERIAL_DEBUG
swSerial.begin(115200);
//swSerialEcho = &swSerial;
#endif
pinMode(led, OUTPUT);
wdt_enable(WDTO_8S);
offtime = millis() - FAN_OFF_TIME;
}
void loop() {
HS inside, outside;
static bool fan = false;
static bool cycle = false;
static long last_time = -(60L * 1000L);
Serial.println();
if (SerialReadUntilDone()) {
//if (init_oled) {
// if (SerialCmdNoError(ONEWIRE_TO_I2C_ROM)) {
// SerialCmdDone(INIT_OLED);
// init_oled = false;
// }
//}
// Read the humidity sensors only once a minute or they will self heat if read too quickly
if (millis() - last_time > 60L * 1000L)
{
if (SerialCmdDone(HUMIDITY_SENSOR_INSIDE))
ReadHumiditySensor(&inside);
if (SerialCmdDone(HUMIDITY_SENSOR_OUTSIDE))
ReadHumiditySensor(&outside);
if (inside.error || outside.error) fan = false;
else {
if (fan) {
if (outside.relative >= OUTSIDE_RELATIVE_FAN_OFF || inside.absolute - outside.absolute <= ABSOLUTE_DELTA_FAN_OFF)
cycle = fan = false;
else {
if (cycle && outside.temp <= MINIMUM_TEMPERATURE &&
millis() - ontime > FAN_ON_TIME) fan = false;
}
if (!fan) offtime = millis();
}
else {
if (outside.relative <= OUTSIDE_RELATIVE_FAN_ON && inside.absolute - outside.absolute >= ABSOLUTE_DELTA_FAN_ON)
cycle = fan = true;
if (cycle && outside.temp <= MINIMUM_TEMPERATURE)
fan = (millis() - offtime > FAN_OFF_TIME) ? true : false;
if (fan) ontime = millis();
}
}
if (fan) SerialCmdDone(FAN_ON);
else SerialCmdDone(FAN_OFF);
if (SerialCmdNoError(ONEWIRE_TO_I2C_ROM)) {
if (init_oled) {
SerialCmdDone(INIT_OLED);
init_oled = false;
}
SerialCmdDone("st13;sc;sf0;sa1;sd70,0,\"INSIDE\";sd127,0,\"OUTSIDE\";sf1;sa0;sd0,12,248,\""
#ifdef FAHRENHEIT
"F"
#else
"C"
#endif
"\";sd0,30,\"%\";sf0;sd0,50,\"g/m\";sd20,46,\"3\";");
SerialPrint("sf1;sa1;sd70,12,\"", C2F(inside.temp), inside.error);
SerialPrint("\";sd70,30,\"", inside.relative, inside.error);
SerialPrint("\";sd70,48,\"", inside.absolute, inside.error);
SerialPrint("\";sd127,12,\"", C2F(outside.temp), outside.error);
SerialPrint("\";sd127,30,\"", outside.relative, outside.error);
SerialPrint("\";sd127,48,\"", outside.absolute, outside.error);
Serial.print("\";");
Serial.print("sf0;sa0;sd0,0,\"");
if (fan) Serial.print("FAN");
else Serial.print("v1.1");
Serial.println("\";sd");
SerialReadUntilDone();
}
else init_oled = true;
last_time = millis();
}
delay(1000);
}
else {
digitalWrite(led, HIGH);
delay(500);
digitalWrite(led, LOW);
delay(500);
init_oled = true;
}
wdt_reset();
}
