Basement/Crawlspace Ventilation System

Intelligently reduce the moisture in your basement/crawlspace to help control mildew growth and lower your heating/cooling bill.

Jan 28, 2019

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environmental sensing

energy efficiency

home automation

Components and supplies

IO Expander Bundle

IO Expander

Arduino Nano R3

Apps and platforms

Arduino IDE

Project description

Code

Basement/Crawlspace Ventilation System

c_cpp

Use the Arduino Nano to create a Smart Ventilation System

1/* IO Expander 
2 *  
3 * Basement/Crawlspace Ventilation System v1.1
4
5  * 
6 */
7
8#include <math.h>
9#include <SoftwareSerial.h>
10#include <avr/wdt.h>
11#include
12  "IOExpander.h"
13
14#define FAHRENHEIT
15#define ONEWIRE_TO_I2C_ROM      "i4s71"
16#define
17  INIT_OLED               "st13;si;sc;sd"
18#define HUMIDITY_SENSOR_INSIDE  "s6t1"
19#define
20  HUMIDITY_SENSOR_OUTSIDE "s8t1"
21#define FAN_ON                  "r1o"
22#define
23  FAN_OFF                 "r1f"
24#define ABSOLUTE_DELTA_FAN_ON   1           //
25  Fan on if absolute humidity delta of inside >= outside 
26#define ABSOLUTE_DELTA_FAN_OFF
27  0.5         // Fan off if absolute humidity delta of inside <= outside
28#define
29  OUTSIDE_RELATIVE_FAN_ON 88          // Fan on if outside relative humidity is <=
30  %
31#define OUTSIDE_RELATIVE_FAN_OFF 90         // Fan off if outside relative
32  humidity is >= %
33#define MINIMUM_TEMPERATURE     15          // Cycle vent on/off
34  if outside temperature <= 15C/59F
35#define FAN_ON_TIME             (20*60*1000L)
36  // 20 min
37#define FAN_OFF_TIME            (20*60*1000L) // 20 min
38
39//#define
40  SERIAL_DEBUG
41#define SERIAL_TIMEOUT  5000                // 5 sec delay between
42  DHT22 reads
43
44#ifdef SERIAL_DEBUG
45SoftwareSerial swSerial(8,7);
46#endif
47
48struct
49  HS {
50  float temp;
51  float relative;
52  float absolute;
53  bool error;
54};
55
56int
57  led = 13;
58bool init_oled = true;
59long ontime, offtime;
60
61#ifdef FAHRENHEIT
62#define
63  C2F(temp)   CelsiusToFahrenheit(temp)
64float CelsiusToFahrenheit(float celsius)
65{
66
67  return ((celsius*9)/5)+32;
68}
69#else
70#define C2F(temp)   (temp)
71#endif
72
73void
74  SerialPrint(const char* str, float decimal, char error)
75{
76  Serial.print(str);
77
78  if (error) Serial.print(F("NA"));
79  else Serial.print(decimal, 1);
80}
81
82float
83  DewPoint(float temp, float humidity)
84{
85  float t = (17.625 * temp) / (243.04
86  + temp);
87  float l = log(humidity/100);
88  float b = l + t;
89  // Use the
90  August-Roche-Magnus approximation
91  return (243.04*b)/(17.625-b);
92}
93
94#define
95  MOLAR_MASS_OF_WATER     18.01534
96#define UNIVERSAL_GAS_CONSTANT  8.21447215
97
98float
99  AbsoluteHumidity(float temp, float relative)
100{
101  //taken from https://carnotcycle.wordpress.com/2012/08/04/how-to-convert-relative-humidity-to-absolute-humidity/
102
103  //precision is about 0.1°C in range -30 to 35°C
104  //August-Roche-Magnus   6.1094
105  exp(17.625 x T)/(T + 243.04)
106  //Buck (1981)     6.1121 exp(17.502 x T)/(T +
107  240.97)
108  //reference https://www.eas.ualberta.ca/jdwilson/EAS372_13/Vomel_CIRES_satvpformulae.html
109    // Use Buck (1981)
110  return (6.1121 * pow(2.718281828, (17.67 * temp) / (temp
111  + 243.5)) * relative * MOLAR_MASS_OF_WATER) / ((273.15 + temp) * UNIVERSAL_GAS_CONSTANT);
112}
113
114void
115  ReadHumiditySensor(HS* hs)
116{
117  SerialCmd("sr");
118  if (SerialReadFloat(&hs->temp)
119  &&
120      SerialReadFloat(&hs->relative)) {
121    //hs->dewpoint = DewPoint(hs->temp,
122  hs->relative);
123    hs->absolute = AbsoluteHumidity(hs->temp, hs->relative);
124
125    hs->error = false;
126  }  
127  else hs->error = true;
128  SerialReadUntilDone();
129}
130
131void
132  setup() {
133  Serial.begin(115200);
134#ifdef SERIAL_DEBUG
135  swSerial.begin(115200);
136
137  //swSerialEcho = &swSerial;
138#endif  
139  pinMode(led, OUTPUT);
140  wdt_enable(WDTO_8S);
141
142  offtime = millis() - FAN_OFF_TIME;
143}
144
145void loop() {
146  HS inside, outside;
147
148  static bool fan = false;
149  static bool cycle = false;
150  static long last_time
151  = -(60L * 1000L);
152
153  Serial.println();
154  if (SerialReadUntilDone()) {
155
156    //if (init_oled) {
157    //  if (SerialCmdNoError(ONEWIRE_TO_I2C_ROM)) {
158
159    //    SerialCmdDone(INIT_OLED);
160    //    init_oled = false;
161    //  }
162
163    //}
164
165    // Read the humidity sensors only once a minute or they will
166  self heat if read too quickly
167    if (millis() - last_time > 60L * 1000L)
168
169    {
170      if (SerialCmdDone(HUMIDITY_SENSOR_INSIDE)) 
171        ReadHumiditySensor(&inside);
172
173  
174      if (SerialCmdDone(HUMIDITY_SENSOR_OUTSIDE))
175        ReadHumiditySensor(&outside);
176
177  
178      if (inside.error || outside.error) fan = false;
179      else {
180
181        if (fan) {
182          if (outside.relative >= OUTSIDE_RELATIVE_FAN_OFF
183  || inside.absolute - outside.absolute <= ABSOLUTE_DELTA_FAN_OFF)
184            cycle
185  = fan = false;
186          else {
187            if (cycle && outside.temp <= MINIMUM_TEMPERATURE
188  && 
189              millis() - ontime > FAN_ON_TIME) fan = false;  
190          }
191
192          if (!fan) offtime = millis();
193        }
194        else {
195          if
196  (outside.relative <= OUTSIDE_RELATIVE_FAN_ON && inside.absolute - outside.absolute
197  >= ABSOLUTE_DELTA_FAN_ON) 
198            cycle = fan = true;
199          if (cycle
200  && outside.temp <= MINIMUM_TEMPERATURE)
201            fan = (millis() - offtime
202  > FAN_OFF_TIME) ? true : false;        
203          if (fan) ontime = millis();
204
205        }
206      }
207  
208      if (fan) SerialCmdDone(FAN_ON);
209      else
210  SerialCmdDone(FAN_OFF);
211  
212      if (SerialCmdNoError(ONEWIRE_TO_I2C_ROM))
213  {
214        if (init_oled) {
215          SerialCmdDone(INIT_OLED);
216          init_oled
217  = false;
218        }
219        SerialCmdDone("st13;sc;sf0;sa1;sd70,0,\\"INSIDE\\";sd127,0,\\"OUTSIDE\\";sf1;sa0;sd0,12,248,\\""
220
221  #ifdef FAHRENHEIT
222            "F" 
223  #else          
224            "C"
225  
226  #endif          
227            "\\";sd0,30,\\"%\\";sf0;sd0,50,\\"g/m\\";sd20,46,\\"3\\";");
228
229        SerialPrint("sf1;sa1;sd70,12,\\"", C2F(inside.temp), inside.error);
230
231        SerialPrint("\\";sd70,30,\\"", inside.relative, inside.error);
232        SerialPrint("\\";sd70,48,\\"",
233  inside.absolute, inside.error);
234        SerialPrint("\\";sd127,12,\\"", C2F(outside.temp),
235  outside.error);
236        SerialPrint("\\";sd127,30,\\"", outside.relative,
237  outside.error);
238        SerialPrint("\\";sd127,48,\\"", outside.absolute,
239  outside.error);
240        Serial.print("\\";");
241        Serial.print("sf0;sa0;sd0,0,\\"");
242
243        if (fan) Serial.print("FAN");
244        else Serial.print("v1.1");
245
246        Serial.println("\\";sd");
247        SerialReadUntilDone();
248      }
249
250      else init_oled = true;
251
252      last_time = millis();
253    }
254
255
256    delay(1000);
257  }
258  else {
259    digitalWrite(led, HIGH);
260    delay(500);
261
262    digitalWrite(led, LOW);
263    delay(500);
264    init_oled = true;
265  }
266
267  wdt_reset();
268}

/* 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();
}

Downloadable files

Basement/Crawlspace Ventilation System

Use the Arduino Nano to create a Smart Ventilation System.

Basement/Crawlspace Ventilation System

Use the Arduino Nano to create a Smart Ventilation System.

Basement/Crawlspace Ventilation System

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