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1 | 1 | /* |
2 | | - NOTE - the order of functions is important for correct |
3 | | - calibration. |
| 2 | + # THIS SKETCH IS NOT NEEDED WITH AUTOCALIBRATION # |
| 3 | + |
| 4 | + Unlike typical sensors, calibration() refers to the zero point where CO2 is 400ppm. |
| 5 | + This 400ppm comes from the average atmospheric value of 400ppm (or atleast was). |
4 | 6 |
|
5 | | - Where other CO2 sensors require an nitrogen atmosphere to "zero" |
6 | | - the sensor CO2 reference, the MHZ19 "zero" (confusingly) refers to the |
7 | | - background CO2 level hardcoded into the device at 400ppm (getBackgroundCO2() |
8 | | - sends a command to the device to retrieve the value); |
| 7 | + Depending on the sensor model, the harcoded value can usually be found by |
| 8 | + calling getBackgroundCO2(); |
9 | 9 |
|
10 | | - The best start for your sensor is to wait till CO2 values are as close to background |
11 | | - levels as possible (currently an average of ~418ppm). Usually at night time and outside |
12 | | - if possible, otherwise when the house has been unoccupied for as long as possible such. |
| 10 | + So if you intend to manually calibrate your sensor, it's usually best to do so at |
| 11 | + night and outside after 20 minutes of run time. |
| 12 | + |
| 13 | + Instead if you're using autocalibration, then the sensor takes the lowest value observed |
| 14 | + in the last 24 hours and adjusts it's self accordingly over a few weeks. |
13 | 15 |
|
14 | 16 | HOW TO USE: |
15 | 17 |
|
16 | 18 | ----- Hardware Method ----- |
17 | 19 | By pulling the zero HD low (0V) for 7 Secs as per the datasheet. |
18 | 20 |
|
19 | 21 | ----- Software Method ----- |
20 | | - Run this example while in an ideal environment (I.e. restarting the device). Once |
21 | | - restarted, disconnect MHZ19 from device and upload a new sketch to avoid |
22 | | - recalibration. |
| 22 | + Run this sketch, disconnect MHZ19 from device after sketch ends (20+ minutes) and upload new |
| 23 | + code to avoid recalibration. |
23 | 24 | |
24 | 25 | ----- Auto calibration ---- |
25 | | - If you are using auto calibration, the sensor will adjust its self every 24 hours |
26 | | - (note here, the auto calibration algorithm uses the lowest observe CO2 value |
27 | | - for that set of 24 hours as the zero - so, if your device is under an environment |
28 | | - which does not fall to these levels, consider turning this off in your setup code). |
| 26 | + As mentioned above if this is set to true, the sensor will adjust it's self over a few weeks |
| 27 | + according to the lowest observed CO2 values each day. *You don't need to run this sketch! |
29 | 28 | |
30 | | - If autoCalibration is set to "false", then getting the background calibration levels |
31 | | - correct at first try is essential. |
32 | 29 | */ |
33 | 30 |
|
34 | 31 | #include <Arduino.h> |
35 | 32 | #include "MHZ19.h" |
36 | | -#include <SoftwareSerial.h> // Remove if using HardwareSerial or non-uno library compatable device |
| 33 | +#include <SoftwareSerial.h> // Remove if using HardwareSerial or non-uno library compatable device |
37 | 34 |
|
38 | | -#define RX_PIN 10 |
| 35 | +#define RX_PIN 10 |
39 | 36 | #define TX_PIN 11 |
40 | | -#define BAUDRATE 9600 // Native to the sensor (do not change) |
| 37 | +#define BAUDRATE 9600 |
41 | 38 |
|
42 | 39 | MHZ19 myMHZ19; |
43 | 40 | SoftwareSerial mySerial(RX_PIN, TX_PIN); // Uno example |
44 | | -//HardwareSerial mySerial(1); // ESP32 Example |
45 | 41 |
|
46 | | -unsigned long getDataTimer = 0; |
| 42 | +unsigned long timeElapse = 0; |
47 | 43 |
|
48 | 44 | void verifyRange(int range); |
49 | 45 |
|
50 | 46 | void setup() |
51 | 47 | { |
52 | 48 | Serial.begin(9600); |
53 | 49 |
|
54 | | - mySerial.begin(BAUDRATE); // Uno example: Begin Stream with MHZ19 baudrate |
55 | | - //mySerial.begin(BAUDRATE, SERIAL_8N1, RX_PIN, TX_PIN); // ESP32 Example |
56 | | - |
57 | | - myMHZ19.begin(mySerial); // *Important, Pass your Stream reference |
58 | | - |
59 | | - /* ### setRange(value)### |
60 | | - Basic: |
61 | | - setRange(value) - set range to value (advise 2000 or 5000). |
62 | | - setRange() - set range to 2000. |
63 | | -
|
64 | | - Advanced: |
65 | | - Use verifyRange(int range) from this code at the bottom. |
66 | | - */ |
67 | | - |
68 | | - myMHZ19.setRange(2000); |
69 | | - |
70 | | - /* ###calibrateZero()### |
71 | | - Basic: |
72 | | - calibrateZero() - request zero calibration |
73 | | -
|
74 | | - Advanced: |
75 | | - In Testing. |
76 | | - */ |
77 | | - |
78 | | - myMHZ19.calibrateZero(); |
79 | | - |
80 | | - /* ### setSpan(value)### |
81 | | - Basic: |
82 | | - setSpan(value) - set span to value (strongly recommend 2000) |
83 | | - setSpan() - set span to 2000; |
84 | | -
|
85 | | - */ |
86 | | - |
87 | | - myMHZ19.setSpan(2000); |
| 50 | + mySerial.begin(BAUDRATE); // sensor serial |
| 51 | + myMHZ19.begin(mySerial); // pass to library |
88 | 52 |
|
89 | | - /* ###autoCalibration(false)### |
90 | | - Basic: |
91 | | - autoCalibration(false) - turns auto calibration OFF. (automatically sent before defined period elapses) |
92 | | - autoCalibration(true) - turns auto calibration ON. |
93 | | - autoCalibration() - turns auto calibration ON. |
94 | | -
|
95 | | - Advanced: |
96 | | - autoCalibration(true, 12) - turns autocalibration ON and calibration period to 12 hrs (maximum 24hrs). |
97 | | - */ |
98 | | - |
99 | | - myMHZ19.autoCalibration(false); |
100 | | - Serial.print("ABC Status: "); myMHZ19.getABC() ? Serial.println("ON") : Serial.println("OFF"); |
101 | | - |
| 53 | + myMHZ19.autoCalibration(false); // make sure auto calibration is off |
| 54 | + Serial.print("ABC Status: "); myMHZ19.getABC() ? Serial.println("ON") : Serial.println("OFF"); // now print it's status |
| 55 | + |
| 56 | + Serial.println("Waiting 20 minutes to stabalise..."); |
| 57 | + /* if you don't need to wait (it's already been this amount of time), remove the next 2 lines */ |
| 58 | + timeElapse = 12e5; // 20 minutes in milliseconds |
| 59 | + while(millis() < timeElapse) {}; // wait this duration |
| 60 | + |
| 61 | + Serial.println("Calibrating.."); |
| 62 | + myMHZ19.calibrate(); // Take a reading which be used as the zero point for 400 ppm |
| 63 | + |
102 | 64 | } |
103 | 65 |
|
104 | 66 | void loop() |
105 | 67 | { |
106 | | - if (millis() - getDataTimer >= 2000) // Check if interval has elapsed (non-blocking delay() equivilant) |
| 68 | + if (millis() - timeElapse >= 2000) // Check if interval has elapsed (non-blocking delay() equivilant) |
107 | 69 | { |
108 | 70 | int CO2; |
109 | 71 | CO2 = myMHZ19.getCO2(); |
110 | 72 |
|
111 | 73 | Serial.print("CO2 (ppm): "); |
112 | 74 | Serial.println(CO2); |
113 | 75 |
|
114 | | - int8_t Temp; // Buffer for temperature |
115 | | - Temp = myMHZ19.getTemperature(); // Request Temperature (as Celsius) |
| 76 | + int8_t Temp; // Buffer for temperature |
| 77 | + Temp = myMHZ19.getTemperature(); // Request Temperature (as Celsius) |
116 | 78 |
|
117 | 79 | Serial.print("Temperature (C): "); |
118 | 80 | Serial.println(Temp); |
119 | 81 |
|
120 | | - getDataTimer = millis(); // Update inerval |
| 82 | + timeElapse = millis(); // Update inerval |
121 | 83 | } |
122 | 84 | } |
123 | | - |
124 | | -void verifyRange(int range) |
125 | | -{ |
126 | | - Serial.println("Requesting new range."); |
127 | | - |
128 | | - myMHZ19.setRange(range); // request new range write |
129 | | - |
130 | | - if (myMHZ19.getRange() == range) // Send command to device to return it's range value. |
131 | | - Serial.println("Range successfully applied."); // Success |
132 | | - |
133 | | - else |
134 | | - Serial.println("Failed to apply range."); // Failed |
135 | | -} |
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