Temperature & Humidity monitoring

Started to build a temp & humidity monitoring system. Yes, it's a ton of them out there already but I didn't make them so they don't count.

The requirements are multiple (more than standard 3) remote temp and humidity sensors that can be inside or outside. A central console connected to computer that receive the data and can log it somewhere.

Starting with remote sensor part I now figured out the parts needed, put them together and done some coding for it.
For initial round I'm going with all off the shelf stuff. Arduino pro mini as the brain, DHT22 as sensor and the dime a dussin 315MHz transmitters from ebay. Did find a case in a local store that seems to be perfect for the remote sensors at least.

Box to be filled

Since I want to run this off 2xAA batteries I also need a booster (the sensor requires at least 3.3v).

Remote Sensor

Coding is simplified by using VirtualWire lib and DHT22 lib. Was going to use jeelib for power saving sleep but for unknown reason jeelib doesn't like the other two (any one of them seems to work, strange) so I ended up grabbing some pieces from internet to make the arduino power down completely for 8 seconds wake up long enough to see that it's not yet time to send and keep sleeping.
Need to remove the power led but with that one still installed I'm down to 3.5mA during sleep and about 22mA when sending data.

Coding I done so far has defined a protocol that is <27 bytes (VirtualWire lib default limit) and still contain all I think I currently need.
Protocol:

• 1 byte: Type of transmitter, 1=temp/humidity, 2=water level, 3-127=reserved for future use
• 1 byte: Protocol format, depends on sensor but format 2 follows (1 is missing mV)
• 4 byte = unit no of the device, basically a random 64bit number (don't think I need the 128bit uuid)
• 2 byte = Sequence number so receiving side know it's same msg
• 2 byte = vcc in mV
• 2 byte = batt mV
• 1 byte DHT22 status of the data
• 2 byte temp*10
• 2 byte humidity*10
• 2 checksum - 2 bytes

I know length is missing but the first two bytes does define format and with that length can be added if the size is dynamic.
Vcc is calculated reading internal 1.1v ref
batt is a separate wire from before the booster

On the receiving side I got it to receive data, separate the different sensors and show a csv or human readable output on the serial port.

Receiver

My current issue is current and presentation.
The remote sensor is taking to much power for to long, considering changing so it only sends the data once and only if status is ok. If that transmission is lost we get it next round.

On the receiving side I'm wondering how to best present the info (besides serial output). The csv output is pretty simple

#Unitno,unitId,msgCnt,vcc mV,batt mV,stat,temp c,humid %
0,13C76FE0,11,4693,4092,0,22.60,42.60
1,2585C230,63,5051,2152,0,21.00,43.30
1,2585C230,65,5096,2076,0,21.00,43.30
0,13C76FE0,12,4693,4092,0,22.60,42.40

No time since then I would need a rtc somewhere and the time is when it's coming so the receiving app can time stamp itself.
I could add a 4x20 lcd but with more than 4 sensors it gets hard to present anything useful.
Thinking of sending it to an raspberry pi where I add it to a database and then have a website that can do the presentation.

One more thing to figure out is distance, how far away can a sensor be and what can be done to increase the range.


Update1: Managed to put it all inside the box

But I think I may have to find another sensor/add 1 battery, the stepup- converter is killing my battery even when idle.

Update2:
Done some testing and decided that the stepup converter must go. Running it on 5V means higher current to start with and the converter does use some power also. I have removed the power LED in the arduino so now it's only on when sending. I also improved the sleep part so it's doing a full power down and let the watchdog start it up every 8 seconds, so time between transmissions need to be a multiple of 8sec.
Some numbers measured with a cheap multimeter.
The battery lifetime is based on 2400mAh batteries, a sampling of about 4 sec (have to check on why so long) and with a rest of 72sec:

Running on 5v from booster, mA after booster:

Active: 15-18ma
Rest: 0.58mA
Batterylife: N/A (70 days - but not really relevant since that's after booster)

mA before boster:

Active: 42-44mA
Rest: 1.49mA
Batterylife: 27 days

Power usage during using 3xAA and no step-up

Active, 3-4 sec, 11mA
Resting - 78sec, .46-.47 mA
Batterylife: 98 days

So if I run on 2 batteries it takes 3x more power during rest than if I run on 3 batteries and no booster (partly because it's then running on 3.6v instead of 5v) and that means 3.6 times longer between battery replacements. While the arduino can run of 2 batteries the sensor requires at least 3.3V so I need 3x.


Version - 0.4 of the remote sensor code, still need a lot of cleanup but it works
 /* /* * RemoteSensor, transmit temp, humidity and some more info * v0.1 - basic transmit, no unitId * v0.2 - unitId in eeprom, better protocol, transmit 4 times, debug mode * v0.3 - Added battery level info * v0.4 - added power sleep mode */ #include <dht.h> #include <VirtualWire.h> #include <EEPROM.h> dht DHT; #define DHT22_PIN 7 #define DHT22_POWER_PIN 12 #define STATUS_PIN 13 #define TRANSMIT_PIN 4 #define DEBUG_PIN 9 #define RESET_PIN 8 long unitId; boolean DEBUG = false; //Powersave stuff // Extracted from http://www.fiz-ix.com/2012/11/low-power-arduino-using-the-watchdog-timer/ // and http://donalmorrissey.blogspot.ca/2010/04/sleeping-arduino-part-5-wake-up-via.html #include <avr/sleep.h> #include <avr/power.h> #include <avr/wdt.h> // This variable is made volatile because it is changed inside // an interrupt function volatile int sleep_count = 0; // Keep track of how many sleep cycles have been completed. int sleep_total = 0; // cycles before end sleep /*************************************************** * Enable the watchdog ***************************************************/ void watchdogOn() { // Clear the reset flag, the WDRF bit (bit 3) of MCUSR. MCUSR &= ~(1 << WDRF); //MCUSR = MCUSR & B11110111; // Set the WDCE bit (bit 4) and the WDE bit (bit 3) // of WDTCSR. The WDCE bit must be set in order to // change WDE or the watchdog prescalers. Setting the // WDCE bit will allow updtaes to the prescalers and // WDE for 4 clock cycles then it will be reset by // hardware. WDTCSR |= (1 << WDCE) | (1 << WDE); // Set the watchdog timeout prescaler value to 1024 K // which will yeild a time-out interval of about 8.0 s. WDTCSR = 1 << WDP0 | 1 << WDP3; /* 8.0 seconds */ /* Enable the WD interrupt (note no reset). */ WDTCSR |= _BV(WDIE); //WDTCSR = WDTCSR | B01000000; //??? MCUSR = MCUSR & B11110111; } /*************************************************** * Enters the arduino into sleep mode. ***************************************************/ void goToSleep() { // The ATmega328 has five different sleep states. // See the ATmega 328 datasheet for more information. // SLEEP_MODE_IDLE -the least power savings // SLEEP_MODE_ADC // SLEEP_MODE_PWR_SAVE // SLEEP_MODE_STANDBY // SLEEP_MODE_PWR_DOWN -the most power savings // I am using the deepest sleep mode from which a // watchdog timer interrupt can wake the ATMega328 set_sleep_mode(SLEEP_MODE_PWR_DOWN); // Set sleep mode. sleep_enable(); // Enable sleep mode. sleep_bod_disable(); // Disable brownout detection sleep_mode(); // Enter sleep mode. // After waking from watchdog interrupt the code continues // to execute from this point. sleep_disable(); // Disable sleep mode after waking. /* Re-enable the peripherals. */ // power_all_enable(); } //goToSleep /*************************************************** * Watchdog Interrupt Service. This * is executed when watchdog timed out. * ***************************************************/ ISR(WDT_vect) { sleep_count ++; // keep track of how many sleep cycles have been completed. } //ISR /*************************************************** * Read input voltage ***************************************************/ long readVcc() { long result; // Read 1.1V reference against AVcc ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1); delay(2); // Wait for Vref to settle ADCSRA |= _BV(ADSC); // Convert while (bit_is_set(ADCSRA, ADSC)); result = ADCL; result |= ADCH << 8; result = 1126400L / result; // Back-calculate AVcc in mV return result; } // readVcc /*************************************************** * Disable ADC when not needed ***************************************************/ void adcDisable() { // Disable the ADC by setting the ADEN bit (bit 7) of the // ADCSRA register to zero. ADCSRA = ADCSRA & B01111111; // Disable the analog comparator by setting the ACD bit // (bit 7) of the ACSR register to one. ACSR = B10000000; // Disable digital input buffers on all analog input pins // by setting bits 0-5 of the DIDR0 register to one. // Of course, only do this if you are not using the analog // inputs for your project. DIDR0 = DIDR0 | B00111111; } //adcDisable /*************************************************** * Enable ADC when needed ***************************************************/ void adcEnable() { // Enable the ADC by setting the ADEN bit (bit 7) of the // ADCSRA register to one. ADCSRA = ADCSRA | B10000000; // Enable the analog comparator by setting the ACD bit // (bit 7) of the ACSR register to zero. ACSR = ACSR & B01111111; // Disable digital input buffers on all analog input pins // by setting bits 0-5 of the DIDR0 register to one. // Of course, only do this if you are not using the analog // inputs for your project. DIDR0 = DIDR0 & B00111110; // only enable adc0 } // adcEnable /*************************************************** * Disable as much as possible before going to sleep ***************************************************/ void prepForSleep() { //Shut off ADC, TWI, SPI, Timer0, Timer1 digitalWrite(DHT22_POWER_PIN, LOW); // power_adc_disable(); // power_twi_disable(); // power_spi_disable(); // power_usart0_disable(); // power_timer0_disable(); //Needed for delay_ms // power_timer1_disable(); //Needed for transmit // power_timer2_disable(); //Needed for asynchronous 32kHz operation power_all_disable(); } // prepForSleep /*************************************************** * Enable functions needed ***************************************************/ void wakeup() { digitalWrite(DHT22_POWER_PIN, HIGH); // adcEnable(); power_adc_enable(); // for batt voltage if (DEBUG) power_usart0_enable(); power_timer0_enable(); //Needed for delay_ms power_timer1_enable(); //Needed for transmit } // wakeup /*************************************************** * Setup everything ***************************************************/ void setup() { long notunitId; int i; Serial.begin(115200); Serial.println("Temp/Humidity remote sensor"); Serial.println(); Serial.print( "Voltage: " ); Serial.print( readVcc(), DEC ); Serial.println("mV"); Serial.print( "Batt voltage: " ); Serial.print( readVcc() / 1024 * analogRead(0), DEC ); // Serial.print( "(" ); // Serial.print( analogRead(0), DEC ); // Serial.print( ")" ); Serial.println("mV"); watchdogOn(); // Initialise the IO and ISR vw_set_tx_pin(TRANSMIT_PIN); // vw_set_rx_pin(RECEIVE_PIN); // vw_set_ptt_pin(TRANSMIT_EN_PIN); // vw_set_ptt_inverted(true); // Required for DR3100 vw_setup(4800); // Bits per sec pinMode(STATUS_PIN, OUTPUT); digitalWrite(STATUS_PIN, LOW); pinMode(DHT22_POWER_PIN, OUTPUT); pinMode(DEBUG_PIN, INPUT_PULLUP); pinMode(RESET_PIN, INPUT_PULLUP); /* Serial.print("EEprom values: "); for(i=0;i<8;i++){ Serial.print(EEPROM.read(i),HEX);Serial.print(' '); } Serial.println(); */ unitId = (long)EEPROM.read(0) << 24 | (long)EEPROM.read(1) << 16 | (long)EEPROM.read(2) << 8 | (long)EEPROM.read(3); notunitId = (long)EEPROM.read(4) << 24 | (long)EEPROM.read(5) << 16 | (long)EEPROM.read(6) << 8 | (long)EEPROM.read(7); if (digitalRead(RESET_PIN) == LOW) { Serial.println("Force generation of a new unitId"); unitId = notunitId = 4711; } if (unitId == -notunitId) { Serial.print("unitId from eeprom: "); Serial.print(unitId, HEX); } else { randomSeed(analogRead(7)*analogRead(6)*analogRead(5) + micros()); unitId = random(); notunitId = -unitId; EEPROM.write(0, unitId >> 24 & 0xFF); EEPROM.write(1, unitId >> 16 & 0xFF); EEPROM.write(2, unitId >> 8 & 0xFF); EEPROM.write(3, unitId & 0xFF); EEPROM.write(4, notunitId >> 24 & 0xFF); EEPROM.write(5, notunitId >> 16 & 0xFF); EEPROM.write(6, notunitId >> 8 & 0xFF); EEPROM.write(7, notunitId & 0xFF); Serial.print("Generated new unitId: "); Serial.print(unitId, HEX); } Serial.println(); // if (digitalRead(DEBUG_PIN) == LOW) { if (digitalRead(DEBUG_PIN) == HIGH) { DEBUG = true; Serial.println("Debug mode detected, transmitting in faster"); sleep_total = 24 / 8; //Must be a multiple of 8 (watchdog timer) } else { DEBUG = false; sleep_total = 72 / 8; //Must be a multiple of 8 (watchdog timer) } Serial.print("SleepTime="); Serial.println(sleep_total); if (DEBUG) { Serial.println("Sensor model,status,Humidity (%),Temperature (C),Time (ms),mV VCC"); } } // setup void loop() { static byte msgA[VW_MAX_MESSAGE_LEN]; //array of bytes to send, lib max is VW_MAX_MESSAGE_LEN bytes static unsigned int msgCnt = 0; //simple counter so receiver knows when it's part of same burst unsigned int chksum, mV, battmV; byte cnt, i; uint32_t start, stop; int chk; // Get ready to take a measurement wakeup(); // READ DATA digitalWrite(STATUS_PIN, HIGH); // Read the temp from the sensor chk = DHT.read22(DHT22_PIN); if (DEBUG) { Serial.print("DHT22, \t"); switch (chk) { case DHTLIB_OK: Serial.print("OK,\t"); break; case DHTLIB_ERROR_CHECKSUM: Serial.print("Checksum error,\t"); break; case DHTLIB_ERROR_TIMEOUT: Serial.print("Time out error,\t"); break; default: Serial.print("Unknown error,\t"); break; } } // if (chk != DHTLIB_ERROR_CHECKSUM) { // No point wasting energy on sending bad data if (chk == DHTLIB_OK) { // No point wasting energy on sending bad data chksum = 0; cnt = 0; msgCnt++; msgA[cnt++] = 1; chksum += msgA[cnt - 1]; // Sensor type=1=temperature/humid msgA[cnt++] = 2; chksum += msgA[cnt - 1]; // Protocol format=2 msgA[cnt++] = unitId >> 24; chksum += msgA[cnt - 1]; msgA[cnt++] = unitId >> 16 & 0xff; chksum += msgA[cnt - 1]; msgA[cnt++] = unitId >> 8 & 0xff; chksum += msgA[cnt - 1]; msgA[cnt++] = unitId & 0xff; chksum += msgA[cnt - 1]; msgA[cnt++] = msgCnt >> 8; chksum += msgA[cnt - 1]; msgA[cnt++] = msgCnt & 0xff; chksum += msgA[cnt - 1]; mV = readVcc(); // input power battmV = mV / 1024 * analogRead(0); // Battery power, separate wire before regulator, must be less than vcc! msgA[cnt++] = mV >> 8; chksum += msgA[cnt - 1]; msgA[cnt++] = mV & 0xff; chksum += msgA[cnt - 1]; msgA[cnt++] = battmV >> 8; chksum += msgA[cnt - 1]; msgA[cnt++] = battmV & 0xff; chksum += msgA[cnt - 1]; msgA[cnt++] = chk; chksum += msgA[cnt - 1]; // send status also msgA[cnt++] = (int)(DHT.temperature * 10) >> 8; chksum += msgA[cnt - 1]; msgA[cnt++] = (int)(DHT.temperature * 10) & 0xff; chksum += msgA[cnt - 1]; msgA[cnt++] = (int)(DHT.humidity * 10) >> 8; chksum += msgA[cnt - 1]; msgA[cnt++] = (int)(DHT.humidity * 10) & 0xff; chksum += msgA[cnt - 1]; msgA[cnt++] = chksum >> 8; // suppose to have built in checksum, still adding one here in case some other library is used msgA[cnt++] = chksum & 0xff; // Serial.println("Sending data"); // send 3 times back 2 back for (i = 0; i < 3; i++) { vw_send((uint8_t *)msgA, cnt); vw_wait_tx(); delay(random(20) * 100); } } // if status isn't checksum err digitalWrite(STATUS_PIN, LOW); // DISPLAY DATA stop = micros(); if (DEBUG) { Serial.print(DHT.humidity, 1); Serial.print(",\t"); Serial.print(DHT.temperature, 1); Serial.print(",\t"); Serial.print((stop - start) / 1000); Serial.print(",\t"); Serial.print(mV); Serial.print(",\t"); Serial.print(battmV); Serial.println(); Serial.print("Bytes sent: "); for (i = 0; i < cnt; i++) { if (msgA[i] < 16) Serial.print('0'); Serial.print(msgA[i], HEX); Serial.print(' '); } Serial.println(); // Serial.print("Sleeping "); // Serial.print(SleepTime); // Serial.println(" seconds"); } // if (chk == DHTLIB_ERROR_CHECKSUM) { // delay(2500); // need to wait at least 2 sec before trying again // } else { Serial.flush(); //to allow serial to finish printing digitalWrite(STATUS_PIN, LOW); //Kill stuff to save power prepForSleep(); digitalWrite(DHT22_POWER_PIN, HIGH); // Serial.print("Start sleeping ");Serial.print(SleepTime);Serial.println(" seconds"); sleep_count = 0; // Start at 0 cycles while (sleep_count <= sleep_total) { if (sleep_count + 1 == sleep_total) { //getting close, warm up the sensor digitalWrite(DHT22_POWER_PIN, HIGH); } goToSleep(); // The watchdog will increase sleep_count } // } digitalWrite(STATUS_PIN, HIGH); start = micros(); }