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My Arduino Mini board has DHT22 temperature sensor and 433MHz radio transmitter modules. I'm using DHT and RCswitch libraries to make use of them. Code looks like this:

void setup() {
  tempSwitch.enableTransmit(RADIO_PIN);
  dht.begin();
}

void loop() {
  float temp = dht.readTemperature();

  unsigned long message = createTemperatureMessage(SENSOR_ID, temp);
  tempSwitch.send(message, 32);

#ifdef MY_DEBUG
  unsigned int sleepCount = 1; 
#else
  // 3600s / 2 / 8s == 225
  unsigned int sleepCount = 225;
#endif
  for (; sleepCount > 0; sleepCount--) {
    LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);
  }
}

So I'm reading temperature and sending it using RCswitch library. Initially I just had delay(1000); instead of fancy LowPower sleep loop but I wanted to make my "device" more battery-friendly so I switched to low-power sleep.

The problem is that now Arduino is only sending data first time and after sleeping 30 minutes (in "release" mode) it does not send anything anymore. If I reduce 30 minutes to 8 seconds it is capable of sending data as well as if I replace sleep with delay(30*60*1000);.

From beyond it looks like something is not caching up after the sleep. Do I need to "wake" radio module in any special way? How to fix that?

1

I've never tried this, but if you are putting the Arduino to sleep I would expect it to cut power to the devices (does it?) if it does then after a 30 minute sleep I would expect the devices to come back up in the initial state. Guessing by your code the initial state of the radio is Tx Disabled, so try moving the

tempSwitch.enableTransmit(RADIO_PIN);

to before the

float temp = dht.readTemperature();

line.

I'd also be concerned that the DHT22 is not in the correct state after you wake up.

Can you try doing a 1 second LowPower sleep in debug mode, I suspect it would work more often.

  • 1
    You idea kind of worked (I just called setup() instead) but with addition of delay(1000); after power-down sleep itself. – Ribtoks Aug 6 '18 at 7:25

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