I am interested in making environmental sensors. One hot topic in this field is dust/pollution sensors.
Among the available low cost modules thare is the DSM 501 sold for about 7 euro by aliexpress
- DSM501.jpg (4.02 KiB) Viewed 8152 times
The outputs are digital and the measurement consists in evauating the time each output stays low in a given time interval (suggested 30 sec).
The details are on the data sheets widely available online, wher also is possible to extract a sort of calibration.
It is clear that these sensor, as well as the cousin GP2Y1010AU, cannot give precise values, but can nevertheless provide usefull information on the change of particulate in the air. I have tested these sensors in my some for about three months and the results are quite interesting: I can clearly see the increase of particulate when there is presence of people in the surrounding, when the house heating is on and when we are cooking.
Having come to know of the espeasy project I wished to include this sensor in the list of available ones.
The problems were:
I haven't found any tutorial on how to make new plugins (I REALLY MISS THIS!!)
The reading process cannot be blocking, as the ESP has other tasks to do (keep the wifi on). So I had to resort to use the interrupts.
In the end I have developep the following plugin, by hacking other plugins.
It works well (with 082 release of espeasy), but I would like to know if someone has some suggestions on how to make it more a "standard" plugin
//#######################################################################################################
//#################################### Plugin 030: DMS501A #############################################
//#################################### by serpa #############################################
//#######################################################################################################
#define PLUGIN_030
#define PLUGIN_ID_030 30
#define PLUGIN_NAME_030 "Dust DMS501A"
#define PLUGIN_VALUENAME1_030 "PM1.0"
#define PLUGIN_VALUENAME2_030 "PM2.5"
unsigned long Plugin_030_pulseCounter[TASKS_MAX];
unsigned long Plugin_030_pulseTotalCounter[TASKS_MAX];
unsigned long Plugin_030_pulseTime[TASKS_MAX];
unsigned long Plugin_030_pulseTimePrevious[TASKS_MAX];
unsigned long tstart1, tstart2;
unsigned long tduration = 30000; // duration of measurement in ms
//unsigned long triggerOn; // start of pulse time in us
//unsigned long triggerOff; // end of pulse time in us
//unsigned long lowpulseoccupancy; // duration of pulse in us
volatile unsigned long thigh1, thigh2;
volatile unsigned long tlow1, tlow2;
volatile unsigned long startlow1, startlow2;
volatile unsigned long starthigh1, starthigh2;
volatile boolean done1, done2;
volatile boolean value1, value2;
//boolean trigger = false;
volatile float ratio1, ratio2;
volatile int DMSpin1, DMSpin2;
float dens1, dens2;
boolean Plugin_030(byte function, struct EventStruct *event, String& string)
{
boolean success = false;
switch (function)
{
case PLUGIN_DEVICE_ADD:
{
Device[++deviceCount].Number = PLUGIN_ID_030;
Device[deviceCount].Type = DEVICE_TYPE_DUAL;
Device[deviceCount].VType = SENSOR_TYPE_TEMP_HUM;
Device[deviceCount].Ports = 0;
Device[deviceCount].PullUpOption = false;
Device[deviceCount].InverseLogicOption = false;
Device[deviceCount].FormulaOption = true;
Device[deviceCount].ValueCount = 2;
Device[deviceCount].SendDataOption = true;
Device[deviceCount].TimerOption = true;
break;
}
case PLUGIN_GET_DEVICENAME:
{
string = F(PLUGIN_NAME_030);
break;
}
case PLUGIN_GET_DEVICEVALUENAMES:
{
strcpy_P(ExtraTaskSettings.TaskDeviceValueNames[0], PSTR(PLUGIN_VALUENAME1_030));
strcpy_P(ExtraTaskSettings.TaskDeviceValueNames[1], PSTR(PLUGIN_VALUENAME2_030));
break;
}
case PLUGIN_WEBFORM_LOAD:
{
char tmpString[128];
sprintf_P(tmpString, PSTR("<TR><TD>Averaging Time (mSec):<TD><input type='text' name='plugin_030' value='%u'>"), Settings.TaskDevicePluginConfig[event->TaskIndex][0]);
string += tmpString;
success = true;
break;
}
case PLUGIN_WEBFORM_SAVE:
{
String plugin1 = WebServer.arg("plugin_030");
Settings.TaskDevicePluginConfig[event->TaskIndex][0] = plugin1.toInt();
// tduration= Settings.TaskDevicePluginConfig[event->TaskIndex][0];
success = true;
break;
}
case PLUGIN_INIT:
{
String log = F("INIT : DSM501A ");
log += Settings.TaskDevicePin1[event->TaskIndex];
addLog(LOG_LEVEL_INFO,log);
// tduration= Settings.TaskDevicePluginConfig[event->TaskIndex][0];
tstart1=millis();
startlow1=micros();
starthigh1=startlow1;
DMSpin1=Settings.TaskDevicePin1[event->TaskIndex];
pinMode(DMSpin1, INPUT);
attachInterrupt(digitalPinToInterrupt(DMSpin1),Plugin_030_ISR1,CHANGE);
tstart2=millis();
startlow2=micros();
starthigh2=startlow2;
DMSpin2=Settings.TaskDevicePin2[event->TaskIndex];
pinMode(DMSpin2, INPUT);
attachInterrupt(digitalPinToInterrupt(DMSpin2),Plugin_030_ISR2,CHANGE);
success = true;
break;
}
case PLUGIN_READ:
{
if (done1 && done2) {
done1=FALSE;
dens1 = ratio1 *110; // ug/m^3
done2=FALSE;
dens2 = ratio2 *110; // ug/m^3
String log = F("DSM501A: PM1.0=");
log += dens1;
log += F(" PM2.5=");
log += dens2;
addLog(LOG_LEVEL_INFO,log);
UserVar[event->BaseVarIndex] = (float) dens1;
UserVar[event->BaseVarIndex + 1] = (float) dens2;
}
success = true;
break;
}
}
return success;
}
/*********************************************************************************************\
* Check Pulse (called from irq handler)
\*********************************************************************************************/
void Plugin_030_ISR1()
{
value1 = digitalRead(DMSpin1); //read input pin just changed
if (value1 == 0) { // gone low
startlow1=micros(); // record starting of low period
thigh1 += startlow1-starthigh1; // record duration of past high state
} else { // gone high
starthigh1=micros(); // record starting of high period
tlow1 += starthigh1-startlow1; // record duration of past low state
}
if (millis()>tstart1+tduration) { // check if average time has past
tstart1 = millis(); // reset time period
ratio1=float(tlow1)/float(thigh1+tlow1)*100; // compute ratio low to total
tlow1=0; // reset low time counter
thigh1=0; // reset high time counter
done1 = TRUE; // set reading complete flag
}
}
/*********************************************************************************************\
* Check Pulse (called from irq handler)
\*********************************************************************************************/
void Plugin_030_ISR2()
{
value2 = digitalRead(DMSpin2); //read input pin just changed
if (value2 == 0) { // gone low
startlow2=micros(); // record starting of low period
thigh2 += startlow2-starthigh2; // record duration of past high state
} else { // gone high
starthigh2=micros(); // record starting of high period
tlow2 += starthigh2-startlow2; // record duration of past low state
}
if (millis()>tstart2+tduration) { // check if average time has past
tstart2 = millis(); // reset time period
ratio2=float(tlow2)/float(thigh2+tlow2)*100; // compute ratio low to high
tlow2=0; // reset low time counter
thigh2=0; // reset high time counter
done2 = TRUE; // set reading complete flag
}
}
///////////////////////////////////////////////////////////////////////////////////////////////////////