# Particle Photon + DHT22: optimizing battery life **URL:** \ **Category:** Hardware\ **Created:** [March 9, 2016, 1:39pm UTC](https://community.particle.io/t/particle-photon-dht22-optimizing-battery-life/20914 "2016-03-09T13:39:44Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![ltpitt](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/ltpitt/32/6710_2.png) [@ltpitt](https://community.particle.io/u/ltpitt)\ **Post date:** [March 9, 2016, 1:39pm UTC](https://community.particle.io/t/particle-photon-dht22-optimizing-battery-life/20914/1 "2016-03-09T13:39:44Z")
Hi all, I have a perfectly working setup of Particle Photon and DHT22. I would like to make it wireless but it works for a very short amount of time on a huge 9200 mAh battery pack. This is 100% related to using sleep and deep sleep. Do you have any suggestions about how to implement this correctly? Is it possible to “permanently” publish a variable in particle cloud so I can let my application retrieve data from cloud and keep my Photon + DHT22 in deep sleep until next update? This is my current code: ``` // Acquire sensor data from Particle Photon // // To read variables from Particle Api use: // https://api.particle.io/v1/devices/YOUR_DEVICE_ID/humidity/?access_token=YOUR_ACCESS_TOKEN // // #include "PietteTech_DHT/PietteTech_DHT.h" #include "math.h" #define DHTTYPE DHT22 // Sensor type DHT11/21/22/AM2301/AM2302 #define DHTPIN D2 // Digital pin for communications // declaration void dht_wrapper(); // must be declared before the lib initialization // library instialization PietteTech_DHT DHT(DHTPIN, DHTTYPE, dht_wrapper); int n; // sensor acquisition counter double temp; // temperature double umid; // humidity double t; // needed in rounding void dht_wrapper() { DHT.isrCallback(); } void setup() { Serial.begin(9600); Serial.println("Device starting..."); Serial.println("DHT Example program using DHT.acquireAndWait"); Serial.print("LIB version: "); Serial.println(DHTLIB_VERSION); Serial.println("---------------"); pinMode(D7, OUTPUT); Particle.variable("humidity", umid); //write the value on the cloud variable called "Humidity" Particle.variable("temperature", temp); //write the value on the cloud variable called "Temperature" } void loop() { Serial.print("\n"); Serial.print(n); Serial.print(": Retrieving information from sensor: "); Serial.print("Read sensor: "); delay(100); int result = DHT.acquireAndWait(); // Error handling switch (result) { case DHTLIB_OK: Serial.println("OK"); break; case DHTLIB_ERROR_CHECKSUM: Serial.println("Error\n\r\tChecksum error"); break; case DHTLIB_ERROR_ISR_TIMEOUT: Serial.println("Error\n\r\tISR time out error"); break; case DHTLIB_ERROR_RESPONSE_TIMEOUT: Serial.println("Error\n\r\tResponse time out error"); break; case DHTLIB_ERROR_DATA_TIMEOUT: Serial.println("Error\n\r\tData time out error"); break; case DHTLIB_ERROR_ACQUIRING: Serial.println("Error\n\r\tAcquiring"); break; case DHTLIB_ERROR_DELTA: Serial.println("Error\n\r\tDelta time to small"); break; case DHTLIB_ERROR_NOTSTARTED: Serial.println("Error\n\r\tNot started"); break; default: Serial.println("Unknown error"); break; } // humidity rounding umid=DHT.getHumidity(); t=umid-floor(umid); // get only decimal part t=t*100; // multiply by 100 decimal part, get xx.xxxxxxxxx t=floor(t); // get only last two characters of decimal part, get yy umid=floor(umid)+(t/100); // temperature rounding temp=DHT.getCelsius(); t=temp-floor(temp); // get only decimal part t=t*100; // multiply by 100 decimal part, get xx.xxxxxxxxx t=floor(t); // get only last two characters of decimal part, get yy temp=floor(temp)+(t/100); // print sensor data to serial Serial.print("Humidity (%): "); Serial.println(DHT.getHumidity(), 2); Serial.print("Temperature (oC): "); Serial.println(DHT.getCelsius(), 2); Serial.print("Temperature (oF): "); Serial.println(DHT.getFahrenheit(), 2); Serial.print("Temperature (K): "); Serial.println(DHT.getKelvin(), 2); Serial.print("Dew Point (oC): "); Serial.println(DHT.getDewPoint()); Serial.print("Dew Point Slow (oC): "); Serial.println(DHT.getDewPointSlow()); // Blink onboard led digitalWrite(D7, HIGH); delay(1000); digitalWrite(D7, LOW); // Increase acquisition counter n++; // Wait for 10 minutes delay(600000); } ``` ---
**Author:** ![MORA](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/mora/32/8575_2.png) [@MORA](https://community.particle.io/u/MORA)\ **Post date:** [March 10, 2016, 10:25am UTC](https://community.particle.io/t/particle-photon-dht22-optimizing-battery-life/20914/2 "2016-03-10T10:25:50Z")
delay does not save power, just halt program execution. You need to use SLEEP\_MODE\_DEEP for the long wait, which will return your program to the start after the duration and all variables that are not persisted will be reset. [https://docs.particle.io/reference/firmware/photon/#sleep-sleep-](https://docs.particle.io/reference/firmware/photon/#sleep-sleep-) ---
**Author:** ![Ric](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/ric/32/514_2.png) [@Ric](https://community.particle.io/u/Ric)\ **Post date:** [March 10, 2016, 4:33pm UTC](https://community.particle.io/t/particle-photon-dht22-optimizing-battery-life/20914/3 "2016-03-10T16:33:09Z")
> [@ltpitt](#): > > is it possible to "permanently" publish a variable in particle cloud No, the Particle cloud does not store data, but there are a lot of free or inexpensive services out there that do (Ubidots, librato, ThingSpeak, etc). ---
**Author:** ![CuriousTech](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/curioustech/32/3315_2.png) [@CuriousTech](https://community.particle.io/u/CuriousTech)\ **Post date:** [March 10, 2016, 8:40pm UTC](https://community.particle.io/t/particle-photon-dht22-optimizing-battery-life/20914/4 "2016-03-10T20:40:38Z")
Use Particle.publish() to publish the data. Particle.variable() only serves a variable when requested (while awake). ---
**Author:** ![ltpitt](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/ltpitt/32/6710_2.png) [@ltpitt](https://community.particle.io/u/ltpitt)\ **Post date:** [March 14, 2016, 1:03pm UTC](https://community.particle.io/t/particle-photon-dht22-optimizing-battery-life/20914/5 "2016-03-14T13:03:33Z")
Are you sure about this? It seems like this works only for events (reading docs now). ---
**Author:** ![MORA](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/mora/32/8575_2.png) [@MORA](https://community.particle.io/u/MORA)\ **Post date:** [March 14, 2016, 2:33pm UTC](https://community.particle.io/t/particle-photon-dht22-optimizing-battery-life/20914/6 "2016-03-14T14:33:08Z")
Particle.publish will publish a value to particle cloud, where it then needs to be picked up by something (subscribe) or trigger a webhook. Publish is an event, but it can carry data with it, so the event could be sensorReading, “25.67” for example.