My Slim 2AA Battery Node

arnoldg

Below is my first sketch with this awsome 2aa battery powerd board.
i didn't measure the current. but i tryed to be as efficient with the power as possible.

my avr is running on 8Mhz, this is becaus the DTH22 doesn't run on 1Mhz.

#include <SPI.h>
#include <MySensor.h>  
#include <DHT.h>  
#include <Vcc.h>


#define CHILD_ID_TEMP 1               // Child id for temperatur
#define CHILD_ID_HUM 2                // Child id for humidity
#define CHILD_ID_VOLT 3               // Child id for battery reading

#define HUMIDITY_SENSOR_DIGITAL_PIN 3 // Where is my DHT22 data pin connected to

int node_id=6;                        // What is my node id

unsigned long SLEEP_TIME =30000UL;    // Sleep time between reads (in milliseconds)
int sleepcycle=1;                     // Counter to count the amout of time not sending data
int humoffset=2;                      // only data is send if humidity is changed for this amout
int tempoffset=0.5;                   // only data is if temperature is changed for this amout 
int gwsendtimout=20;                  // each 20*sleep_time (10 minutes) data will be send

const float VccMin   = 1.5;           // Minimum expected Vcc level, in Volts.
const float VccMax   = 3.0;           // Maximum expected Vcc level, in Volts.
const float VccCorrection = 1.0/1.0;  // Measured Vcc by multimeter divided by reported Vcc

Vcc vcc(VccCorrection);

MySensor gw;
DHT dht;
//Store last values
float lastTemp = 0 ;                  
float lastHum = 0 ;
float batteryV=0;
int oldBatteryPcnt = 0;             

boolean lastTripped = false ;
boolean metric = true; 

boolean gwsend = true;              // to determin if data has to be send

MyMessage msgHum(CHILD_ID_HUM, V_HUM);
MyMessage msgTemp(CHILD_ID_TEMP, V_TEMP);
MyMessage msgVolt(CHILD_ID_VOLT, V_VOLTAGE);

void setup()  
{ 
  gw.begin(NULL,node_id,false);
  dht.setup(HUMIDITY_SENSOR_DIGITAL_PIN); 

  // Send the Sketch Version Information to the Gateway
  gw.sendSketchInfo("Humidity", "1.1",true);


 
  // Register all sensors to gw (they will be created as child devices)
  gw.present(CHILD_ID_HUM, S_HUM,"Humidity douche");
  gw.present(CHILD_ID_TEMP, S_TEMP,"Temperatuur douche");
  gw.present(CHILD_ID_VOLT, S_MULTIMETER,"Battery voltage");
   
  metric = gw.getConfig().isMetric;
}

void loop()      

{  
  // get the battery Voltage
   batteryV  = vcc.Read_Volts();
   int batteryPcnt = vcc.Read_Perc(VccMin, VccMax);

   if (oldBatteryPcnt != batteryPcnt) {
     // Power up radio after sleep
     gwsend=true;
     oldBatteryPcnt = batteryPcnt;
   }
    
  delay(dht.getMinimumSamplingPeriod());

  float temp1 = dht.getTemperature();
  float humidity = dht.getHumidity();

  if (isnan(temp1)) {
//      Serial.println("Failed reading temperature from DHT");
  } else if ((temp1 <= lastTemp-tempoffset)||(temp1 >= lastTemp+tempoffset)) {
    lastTemp = temp1;
    if (!metric) {
      temp1 = dht.toFahrenheit(temp1);
    }
    gwsend=true;
  }

  if (isnan(humidity)) {
    //      Serial.println("Failed reading humidity from DHT");
  } else if ((humidity <= lastHum-humoffset)||(humidity >= lastHum+humoffset)) {
      lastHum = humidity;
      gwsend=true;
    }

  if (sleepcycle>gwsendtimout){
    gwsend=true;
   }

if (gwsend){     
    gw.sendBatteryLevel(oldBatteryPcnt);
    gw.send(msgVolt.set(batteryV, 1));
    gw.send(msgTemp.set(lastTemp, 1));  
    gw.send(msgHum.set(lastHum, 1));
    gwsend=false;
    sleepcycle=1;
  }
  sleepcycle++;  
  gw.sleep(SLEEP_TIME);
}

wergeld

Finally had time to solder it. Not my best job, I admit. One of the caps I tried to mount was not flush enough so I had to clip it off. Hopefully not a critical component! I made the radio removable using some header strips. Now to figure out what temp sensor to use. I have currently used just a thermister. Can DHT22 work down at ~1.9V?

Anyway this was fun - highly recommend a needle point solder tip!

AWI

@wergeld congratulations :thumbsup:
For the temp sensor I suggest a si7021 board. Almost the same price as as dht22 but more accurate, reliable and versatile. It uses the I2C bus (pin A4, A5)

wergeld

@AWI said:

@wergeld congratulations :thumbsup:
For the temp sensor I suggest a si7021 board. Almost the same price as as dht22 but more accurate, reliable and versatile. It uses the I2C bus (pin A4, A5)

@AWI I saw the si7021 on another forum. Ordered a couple of the low voltage ones as I want to make my nodes with as few components as possible. I could still use my thermistor while I wait. This is a fun build!

Soloam

Hello, I made a small modification to this project, hope that is ok! Now I need some help validating it! I opened a new topic to avoid going side topic in this one:

http://forum.mysensors.org/topic/3642/m26872-slim-node-mod

Thank you all

m26872

@Soloam I'm happy that you've picked up the design. That's what this openhardware is all about. Also very good that you made a new topic! So, let's continue there. I'll follow.

rollercontainer

I ordered a proto pack on 15th of April and received it on 30th of April. Pretty fast, I think. :-)

rollercontainer

Hm, I built some nodes and messured the current with a Fluke 179: 15mA even with a minimal sketch with sleeping enabled. AVRs are not from china, but the NRF24 are. So, is the radio the problem?

Greetings

rollercontainer

(i am using MySensors 2.0.0beta)

m26872

Could be radio, but who knows? What troubleshooting steps have you taken? Hw-, sw-variations etc. Please post your sketch. Perhaps are there any SlimNode users with working MyS 2.0.0 beta that can share some info.

GertSanders

@m26872
I have had a bad radio which would not go to sleep and consumed around that amount all the time (also when I used SLEEP in the 2.0 library).

Switching the radio to another one fixed it. All my radio's are from China, so they are normally OK. But you can get bad ones once in a while. Given the low cost I do not care and swap them when needed.

rollercontainer

Ok, where to buy NRF24's which are genuine for sure and not too expensive in europe?

GertSanders

@rollercontainer
No idea, I'm quite happy with the radio's from China (1 bad one on 25 pcs so far).

rollercontainer

Thx, Gert. Are you using 1.5 or 2.0.0beta?

GertSanders

@rollercontainer
I use the 2.0 beta

rollercontainer

Bought another 2 radios from different dealers. The one with the blob on the die is going down to 2mA, but isnt working at all (node does not come up). The next one is working, but again 15mA. This is frustrating. Anyone here with a good source for radio modules?

Even with a stripped down sketch without any sensors with only delay and sleep in the loop, the current stays the same.

GertSanders

@rollercontainer
I get my radio's from an Aliexpress store called AAA+ (or something with a lot of A's in the name).

Bobcat

@26872, It's my first post here and I had to register so that I could give you my regards for your work and for sharing it with us! Just ordered a batch of your v2 boards.

I have similar design sensors running on proto-pcbs, but your ready-made pcb makes everything much more convenient.

Just had a question on stability of running regular Arduino 8mhz internal clock bootloader for prolonged time. Anyone tried this and had success running the 328 down to 2v (or so) @ 8mhz? If this is a doomed idea, I will have to attach the boost circuit to this design, but it would be nice to avoid all that parasite current consumption.

GertSanders

@Bobcat
I have had an atmega328 run down to 1V6 at 8Mhz before failing completely, so working down to 2V should be OK. The nrf24 will likely stop around that point as well (lower limit is 1V9 for that chip).

Bobcat

@GertSanders
Thank you for the reply! Was the atmega doing some clock critical tasks when it went below 2v? I am thinking to attach BME280 (Pressure/Temp/Hum) which also operates in the same voltage range, but not sure if the I2C will be working properly when atmega goes overclocked.

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