Arduino nano, soil moisture sensor, four relays and a burnt AA battery holder

Hello,

I'm trying to build a battery operated automatic garden irrigation system, using

  • 1x arduino nano
  • 2x two relays controllers
  • 1x soil moisture sensor.
  • 1x 9v solenoid latching valve

I need the four relays because to operate the latching valve I need to be able to invert polarity.

I connected all, programmed, and tested connected to my computer via a USB cable, it all works as expected.

then I tried connecting it to batteries, initially I thought powering the whole thing with a 9V PP3 battery connected to Vin and gnd, but it won't work, I guess the relays absorb too much power.

I then switched to powering the thing with 4x 1,5V AA batteries and use the PP3 just in the relays, and all seemed well, and I was getting ready to solder my stripboard with other pieces, while the breadboard test was still operating. I suddenly smelled burnt plastic, and found that the AA battery holder was melting down as the batteries were overheating.

Now I'm left with the power problem, I don't know how to power this circuit. because there's water involved I would really prefer using batteries, but I don't know how.

here's a photo of my breadboard test: Imgur: The magic of the Internet

thanks

Hi @dongiulio
I suggest you use LI-IO batteries, type 18650 together with a charger/stepup to get the 5V for the arduino.
With this device you can use up to 2 batteries in parallel.
Are the relays 5v too?
charge_step-up

RV mineirin

Better use a H-bridge like in DC motor controllers. Use one with MOSFETs, not those old L2... chips. With integrated H-bridges it's hard until impossible to produce short circuits.

I power my plant watering project with a mains in/5V out module, https://smile.amazon.com/gp/product/B07V5XP92F/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1.

You could use a wall wart, like this https://smile.amazon.com/gp/product/B01M0ISMJ5/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 to power your project.

I used this motor https://smile.amazon.com/gp/product/B07BZMPR4F/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I only needed a single relay.

I used this valve to stop siphon water flow, https://smile.amazon.com/gp/product/B07XDS142G/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

And I use this code:

#include <ESP32Time.h>
#include <WiFi.h>
#include <PubSubClient.h>
#include "certs.h" // include the connection info for WiFi and MQTT
#include "sdkconfig.h" // used for log printing
#include "esp_system.h"
#include "freertos/FreeRTOS.h" //freeRTOS items to be used
#include "freertos/task.h"
#include <driver/adc.h>
#include <SimpleKalmanFilter.h>
////
WiFiClient      wifiClient; // do the WiFi instantiation thing
PubSubClient    MQTTclient( mqtt_server, mqtt_port, wifiClient ); //do the MQTT instantiation thing
ESP32Time       rtc;
////
#define evtDoParticleRead  ( 1 << 0 ) // declare an event
#define evtADCreading      ( 1 << 3 )
EventGroupHandle_t eg; // variable for the event group handle
////
SemaphoreHandle_t sema_MQTT_KeepAlive;
SemaphoreHandle_t sema_mqttOK;
////
QueueHandle_t xQ_RemainingMoistureMQTT;
QueueHandle_t xQ_RM;
QueueHandle_t xQ_Message;
////
struct stu_message
{
  char payload [150] = {'\0'};
  String topic;
} x_message;
////
int    mqttOK = 0;
bool   TimeSet = false;
bool   manualPumpOn = false;
////
// interrupt service routine for WiFi events put into IRAM
void IRAM_ATTR WiFiEvent(WiFiEvent_t event)
{
  switch (event) {
    case SYSTEM_EVENT_STA_CONNECTED:
      break;
    case SYSTEM_EVENT_STA_DISCONNECTED:
      log_i("Disconnected from WiFi access point");
      break;
    case SYSTEM_EVENT_AP_STADISCONNECTED:
      log_i("WiFi client disconnected");
      break;
    default: break;
  }
} // void IRAM_ATTR WiFiEvent(WiFiEvent_t event)
////
void IRAM_ATTR mqttCallback(char* topic, byte * payload, unsigned int length)
{
  // clear locations
  memset( x_message.payload, '\0', 150 );
  x_message.topic = ""; //clear string buffer
  x_message.topic = topic;
  int i = 0;
  for ( i; i < length; i++)
  {
    x_message.payload[i] = ((char)payload[i]);
  }
  x_message.payload[i] = '\0';
  xQueueOverwrite( xQ_Message, (void *) &x_message );// send data
} // void mqttCallback(char* topic, byte* payload, unsigned int length)
////
void setup()
{
  x_message.topic.reserve(150);
  //
  xQ_Message = xQueueCreate( 1, sizeof(stu_message) );
  xQ_RemainingMoistureMQTT = xQueueCreate( 1, sizeof(float) ); // sends a queue copy
  xQ_RM = xQueueCreate( 1, sizeof(float) );
  //
  eg = xEventGroupCreate(); // get an event group handle
  //
  sema_mqttOK =  xSemaphoreCreateBinary();
  xSemaphoreGive( sema_mqttOK );
  //
  gpio_config_t io_cfg = {}; // initialize the gpio configuration structure
  io_cfg.mode = GPIO_MODE_INPUT; // set gpio mode. GPIO_NUM_0 input from water level sensor
  io_cfg.pull_down_en = GPIO_PULLDOWN_ENABLE; // enable pull down
  io_cfg.pin_bit_mask = ( (1ULL << GPIO_NUM_0) ); //bit mask of the pins to set, assign gpio number to be configured
  gpio_config(&io_cfg); // configure the gpio based upon the parameters as set in the configuration structure
  //
  io_cfg = {}; //set configuration structure back to default values
  io_cfg.mode = GPIO_MODE_OUTPUT;
  io_cfg.pin_bit_mask = ( 1ULL << GPIO_NUM_4 | (1ULL << GPIO_NUM_5) ); //bit mask of the pins to set, assign gpio number to be configured
  gpio_config(&io_cfg);
  gpio_set_level( GPIO_NUM_4, LOW); // deenergize relay module
  gpio_set_level( GPIO_NUM_5, LOW); // deenergize valve
  // set up A:D channels  https://dl.espressif.com/doc/esp-idf/latest/api-reference/peripherals/adc.html
  adc1_config_width(ADC_WIDTH_12Bit);
  adc1_config_channel_atten(ADC1_CHANNEL_3, ADC_ATTEN_DB_11);// using GPIO 39
  //
  xTaskCreatePinnedToCore( MQTTkeepalive, "MQTTkeepalive", 10000, NULL, 6, NULL, 1 );
  xTaskCreatePinnedToCore( fparseMQTT, "fparseMQTT", 10000, NULL, 5, NULL, 1 ); // assign all to core 1, WiFi in use.
  xTaskCreatePinnedToCore( fPublish, "fPublish", 9000, NULL, 3, NULL, 1 );
  xTaskCreatePinnedToCore( fReadAD, "fReadAD", 9000, NULL, 3, NULL, 1 );
  xTaskCreatePinnedToCore( fDoMoistureDetector, "fDoMoistureDetector", 70000, NULL, 4, NULL, 1 );
  xTaskCreatePinnedToCore( fmqttWatchDog, "fmqttWatchDog", 3000, NULL, 2, NULL, 1 );
} //void setup()
////
void fReadAD( void * parameter )
{
  float    ADbits = 4096.0f;
  float    uPvolts = 3.3f;
  float    adcValue_b = 0.0f; //plant in yellow pot
  uint64_t TimePastKalman  = esp_timer_get_time(); // used by the Kalman filter UpdateProcessNoise, time since last kalman calculation
  float    WetValue = 1.07f; // value found by putting sensor in water
  float    DryValue = 2.732f; // value of probe when held in air
  float    Range = DryValue - WetValue;
  float    RemainingMoisture = 100.0f;
  SimpleKalmanFilter KF_ADC_b( 1.0f, 1.0f, .01f );
  for (;;)
  {
    xEventGroupWaitBits (eg, evtADCreading, pdTRUE, pdTRUE, portMAX_DELAY ); //
    adcValue_b = float( adc1_get_raw(ADC1_CHANNEL_3) ); //take a raw ADC reading
    adcValue_b = ( adcValue_b * uPvolts ) / ADbits; //calculate voltage
    KF_ADC_b.setProcessNoise( (esp_timer_get_time() - TimePastKalman) / 1000000.0f ); //get time, in microsecods, since last readings
    adcValue_b = KF_ADC_b.updateEstimate( adcValue_b ); // apply simple Kalman filter
    TimePastKalman = esp_timer_get_time(); // time of update complete
    RemainingMoisture = 100.0f * (1 - ((adcValue_b - WetValue) / (DryValue - WetValue))); //remaining moisture =  1-(xTarget - xMin) / (xMax - xMin) as a percentage of the sensor wet dry volatges
    xQueueOverwrite( xQ_RM, (void *) &RemainingMoisture );
    //log_i( "adcValue_b = %f remaining moisture %f%", adcValue_b, RemainingMoisture );
  }
  vTaskDelete( NULL );
}
////
void fPublish( void * parameter )
{
  float  RemainingMoisture = 100.0f;
  for (;;)
  {
    if ( xQueueReceive(xQ_RemainingMoistureMQTT, &RemainingMoisture, portMAX_DELAY) == pdTRUE )
    {
      xSemaphoreTake( sema_MQTT_KeepAlive, portMAX_DELAY ); // whiles MQTTlient.loop() is running no other mqtt operations should be in process
      MQTTclient.publish( topicRemainingMoisture_0, String(RemainingMoisture).c_str() );
      xSemaphoreGive( sema_MQTT_KeepAlive );
    }
  } // for (;;)
  vTaskDelete( NULL );
} //void fPublish( void * parameter )
////
void WaterPump0_off()
{
  gpio_set_level( GPIO_NUM_4, LOW); //denergize relay module
  vTaskDelay( 1 );
  gpio_set_level( GPIO_NUM_5, LOW); //denergize/close valve
}
////
void WaterPump0_on()
{
  gpio_set_level( GPIO_NUM_5, HIGH); //energize/open valve
  vTaskDelay( 1 );
  gpio_set_level( GPIO_NUM_4, HIGH); //energize relay module
}
////
void fmqttWatchDog( void * paramater )
{
  int UpdateImeTrigger = 86400; //seconds in a day
  int UpdateTimeInterval = 85000; // get another reading when = UpdateTimeTrigger
  int maxNonMQTTresponse = 12;
  TickType_t xLastWakeTime = xTaskGetTickCount();
  const TickType_t xFrequency = 5000; //delay for mS
  for (;;)
  {
    xLastWakeTime = xTaskGetTickCount();
    vTaskDelayUntil( &xLastWakeTime, xFrequency );
    xSemaphoreTake( sema_mqttOK, portMAX_DELAY ); // update mqttOK
    mqttOK++;
    xSemaphoreGive( sema_mqttOK );
    if ( mqttOK >= maxNonMQTTresponse )
    {
      ESP.restart();
    }
    UpdateTimeInterval++; // trigger new time get
    if ( UpdateTimeInterval >= UpdateImeTrigger )
    {
      TimeSet = false; // sets doneTime to false to get an updated time after a days count of seconds
      UpdateTimeInterval = 0;
    }
  }
  vTaskDelete( NULL );
} //void fmqttWatchDog( void * paramater )
////
void fDoMoistureDetector( void * parameter )
{
  //wait for a mqtt connection
  while ( !MQTTclient.connected() )
  {
    vTaskDelay( 250 );
  }
  int      TimeToPublish = 5000000; //5000000uS
  int      TimeForADreading = 100 * 1000; // 100mS
  uint64_t TimePastPublish = esp_timer_get_time(); // used by publish
  uint64_t TimeADreading   = esp_timer_get_time();
  TickType_t xLastWakeTime = xTaskGetTickCount();
  const TickType_t xFrequency = 10; //delay for 10mS
  float    RemainingMoisture = 100.0f; //prevents pump turn on during start up
  bool     pumpOn = false;
  uint64_t PumpOnTime = esp_timer_get_time();
  int      PumpRunTime = 11000000;
  uint64_t PumpOffWait = esp_timer_get_time();
  uint64_t PumpOffWaitFor = 60000000; //one minute
  float    lowMoisture = 23.0f;
  float    highMoisture = 40.0f;
  for (;;)
  {
    //read AD values every 100mS.
    if ( (esp_timer_get_time() - TimeADreading) >= TimeForADreading )
    {
      xEventGroupSetBits( eg, evtADCreading );
      TimeADreading = esp_timer_get_time();
    }
    xQueueReceive(xQ_RM, &RemainingMoisture, 0 ); //receive queue stuff no waiting
    //read gpio 0 is water level good. Yes: OK to run pump : no pump off.   remaining moisture good, denergize water pump otherwise energize water pump.
    if ( RemainingMoisture >= highMoisture )
    {
      WaterPump0_off();
    }
    if ( !pumpOn )
    {
      log_i( "not pump on ");
      if ( gpio_get_level( GPIO_NUM_0 ) )
      {
        if ( RemainingMoisture <= lowMoisture )
        {
          //has one minute passed since last pump energize, if so then allow motor to run
          if ( (esp_timer_get_time() - PumpOffWait) >= PumpOffWaitFor )
          {
            WaterPump0_on();
            log_i( "pump on " );
            pumpOn = !pumpOn;
            PumpOnTime = esp_timer_get_time();
          }
        }
        //xSemaphoreGive( sema_RemainingMoisture );
      } else {
        log_i( "water level bad " );
        WaterPump0_off();
        PumpOffWait = esp_timer_get_time();
      }
    } else {
      /*
         pump goes on runs for 5 seconds then turn off, then wait PumpOffWaitTime before being allowed to energize again
      */
      if ( (esp_timer_get_time() - PumpOnTime) >= PumpRunTime )
      {
        log_i( "pump off " );
        WaterPump0_off(); // after 5 seconds turn pump off
        pumpOn = !pumpOn;
        PumpOffWait = esp_timer_get_time();
      }
    }
    // publish to MQTT every 5000000uS
    if ( (esp_timer_get_time() - TimePastPublish) >= TimeToPublish )
    {
      xQueueOverwrite( xQ_RemainingMoistureMQTT, (void *) &RemainingMoisture );// data for mqtt publish
      TimePastPublish = esp_timer_get_time(); // get next publish time
    }
    xLastWakeTime = xTaskGetTickCount();
    vTaskDelayUntil( &xLastWakeTime, xFrequency );
  }
  vTaskDelete( NULL );
}// end fDoMoistureDetector()
////
void MQTTkeepalive( void *pvParameters )
{
  sema_MQTT_KeepAlive   = xSemaphoreCreateBinary();
  xSemaphoreGive( sema_MQTT_KeepAlive ); // found keep alive can mess with a publish, stop keep alive during publish
  MQTTclient.setKeepAlive( 90 ); // setting keep alive to 90 seconds makes for a very reliable connection, must be set before the 1st connection is made.
  TickType_t xLastWakeTime = xTaskGetTickCount();
  const TickType_t xFrequency = 250; // 250mS
  for (;;)
  {
    //check for a is-connected and if the WiFi 'thinks' its connected, found checking on both is more realible than just a single check
    if ( (wifiClient.connected()) && (WiFi.status() == WL_CONNECTED) )
    {
      xSemaphoreTake( sema_MQTT_KeepAlive, portMAX_DELAY ); // whiles MQTTlient.loop() is running no other mqtt operations should be in process
      MQTTclient.loop();
      xSemaphoreGive( sema_MQTT_KeepAlive );
    }
    else {
      log_i( "MQTT keep alive found MQTT status %s WiFi status %s", String(wifiClient.connected()), String(WiFi.status()) );
      if ( !(wifiClient.connected()) || !(WiFi.status() == WL_CONNECTED) )
      {
        connectToWiFi();
      }
      connectToMQTT();
    }
    xLastWakeTime = xTaskGetTickCount();
    vTaskDelayUntil( &xLastWakeTime, xFrequency );
  }
  vTaskDelete ( NULL );
}
////
void connectToMQTT()
{
  // create client ID from mac address
  byte mac[5];
  int count = 0;
  WiFi.macAddress(mac); // get mac address
  String clientID = String(mac[0]) + String(mac[4]);
  log_i( "connect to mqtt as client %s", clientID );
  while ( !MQTTclient.connected() )
  {
    MQTTclient.disconnect();
    MQTTclient.connect( clientID.c_str(), mqtt_username, mqtt_password );
    vTaskDelay( 250 );
    count++;
    if ( count == 5 )
    {
      ESP.restart();
    }
  }
  MQTTclient.setCallback( mqttCallback );
  MQTTclient.subscribe( topicOK );
}
////
void connectToWiFi()
{
  int TryCount = 0;
  while ( WiFi.status() != WL_CONNECTED )
  {
    TryCount++;
    WiFi.disconnect();
    WiFi.begin( SSID, PASSWORD );
    vTaskDelay( 4000 );
    if ( TryCount == 10 )
    {
      ESP.restart();
    }
  }
  WiFi.onEvent( WiFiEvent );
} // void connectToWiFi()
//////
void fparseMQTT( void *pvParameters )
{
  struct stu_message px_message;
  for (;;)
  {
    if ( xQueueReceive(xQ_Message, &px_message, portMAX_DELAY) == pdTRUE )
    {
      if ( px_message.topic == topicOK )
      {
        xSemaphoreTake( sema_mqttOK, portMAX_DELAY );
        mqttOK = 0; // clear mqtt ok count
        xSemaphoreGive( sema_mqttOK );
      }
      if ( !TimeSet )
      {
        String temp = "";
        temp = px_message.payload[0];
        temp += px_message.payload[1];
        temp += px_message.payload[2];
        temp += px_message.payload[3];
        int year =  temp.toInt();
        temp = "";
        temp = px_message.payload[5];
        temp += px_message.payload[6];
        int month =  temp.toInt();
        temp = "";
        temp = px_message.payload[8];
        temp += px_message.payload[9];
        int day =  temp.toInt();
        temp = "";
        temp = px_message.payload[11];
        temp += px_message.payload[12];
        int hour =  temp.toInt();
        temp = "";
        temp = px_message.payload[14];
        temp += px_message.payload[15];
        int min =  temp.toInt();
        rtc.setTime( 0, min, hour, day, month, year );
        log_i( "%s  ", rtc.getTime() );
        TimeSet = true;
      }
      // manual pump control
      if ( str_eTopic == topicPumpState )
      {
        if ( String(strPayload) == "off" )
        {
          WaterPump0_off();
          manualPumpOn = false;
        }
        if ( String(strPayload) == "on" )
        {
          WaterPump0_on();
          manualPumpOn = true;
        }
      }
    }
  } //for(;;)
  vTaskDelete ( NULL );
} // void fparseMQTT( void *pvParameters )
////
void loop() {}

Perhaps you can find some of the code useful.`

Thanks for your reply.

yeah, the relays are 5v,

What is that device?

Thanks,
G

Wow, that's impressive, thanks, I take you have a water reservoir placed above your ground, and you just need the water pump to start the syphon.

In my system the irrigation water arrives with pressure from a pump that I already use (a strong pump), I just need a system to 'open/close the faucet'

Hi,
@dongiulio image,

Can you please post a circuit diagram?

Tom... :smiley: :+1: :coffee: :australia:

would you have an example of what I should look for?

My reservoir is at ground level, the pump has to self prime and pull the water out of the reservoir.

If you got pressure, all you need is a valve to open and close to allow flow.

A shot of the resevoir

A shot of the motor and valve,

Boxed project,

uhm, still not sure what it does or how to use it.

by the way I forgot to mention what is probably obvious, the batteries I use for this device should no drain too quick. ideally several months.

You are seriously joking? :crazy_face:

Short circuit somewhere.

No, you need a mains power supply, but one that is made and sold by reputable dealers.

uhm, I guess I'll have to give up my dream of operating it by batteries.

I have a few of these hi-link 9v 20W converters would they work?

There are latching valves made specifically for battery powered irrigation systems, so long duration operation should not be a problem with that part. Replacing the mechanical relays with an h-bridge will save considerable power. The pump definitely needs serious power, better to elevate the tank, or use a solar panel if mains power is unavailable.

Search a bit, there are valves that have two coils to eliminate the need to reverse polarity.

thanks, but I already invested on the single solenoid latching valves, I didn't know these existed. they're not cheap anyways

The high current draw from the battery would likely be caused by switching the relays in such a way that there is a direct path between the + and - terminals of the battery. Doing this for even a fraction of a second can weld the relay contacts, so check with an ohmmeter before doing any further testing.

The relays were not connected to anything. When the melting occurred I was just testing if the circuit would activate the relays in the right order and at the right time.

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