@electrik Not sure what it would be at 8.4v because that would be two fully charged 18650's and the two I have on test are currently giving 7.80v on the multimeter and returning about 870 on the serial monitor, reporting battery at 0.94v and 86%

I would need to fully recharge two batteries later to tell what the max would be.

@mfalkvidd been there already but thanks.

@electrik Hi, the 2.2Meg is connected to the battery and the 330k is connected to GND.

Cheers

@mfalkvidd Well thanks for looking at it, at least my maths is still working ok! Perhaps someone else may know whats going on...

The strange thing is if I use this line-:

float batteryV = sensorValue * 8.6 / 1023;

I can get close. I found another thread where @TimO was using 7.2v with this in his sketch-:

float batteryV = sensorValue * 6.1 / 1023;

So I just increased the 6.1 slowly until my read value was close to my multimeter voltage. But I dont understand what the 6.1 in this line of code is doing, or where it comes from...

@mfalkvidd I have left the analogReference as it was in the original like this-:

void setup()
{
	// use the 1.1 V internal reference
#if defined(__AVR_ATmega2560__)
	analogReference(INTERNAL1V1);
#else
	analogReference(INTERNAL);
#endif
}

void presentation()
{
	// Send the sketch version information to the gateway and Controller
	sendSketchInfo("Battery Meter", "1.0");
}

Just for learning about battery monitoring, I am using a Nano with two 18650's in series to power it. in my final project I will be using a Pro Mini. Unfortunately the ultrasonic sensor I need to use is a 5v sensor and needs a good supply. Hence learning about monitoring the 18650's.
Cheers.

Thanks for the reply.

Hi Guys,

I have been playing around with the Battery Powered Sensor sketch, trying to get it to report correctly the level of 2x 18650 batteries. I am not a programmer and am getting a bit lost with the sketch. I have a voltage divider of 2.2Meg and 330K, So in my calculations 2 x 18650 batteries give me a max voltage of 8.4vdc fully charged, therefore with that divider Vout should be 1.096vdc or around that. So I have calculated that my Vmax is 1.100007332 and my Volts per bit for the sketch should be 0.001075275.
But when I run the sketch I am getting around 1vdc on the serial monitor, when the voltmeter is reading 7.90vdc

Heres the Loop part of my sketch, can some one point out my mistakes please?

void loop()
{
	// get the battery Voltage
	int sensorValue = analogRead(BATTERY_SENSE_PIN);
#ifdef MY_DEBUG
	Serial.println(sensorValue);
#endif

	// 1M, 470K divider across battery and using internal ADC ref of 1.1V
	// Sense point is bypassed with 0.1 uF cap to reduce noise at that point
	// ((1e6+470e3)/470e3)*1.1 = Vmax = 3.44 Volts
	// 3.44/1023 = Volts per bit = 0.003363075

	int batteryPcnt = sensorValue / 10;

#ifdef MY_DEBUG
	float batteryV  = sensorValue * 0.001075275;
 
	Serial.print("Battery Voltage: ");
	Serial.print(batteryV);
	Serial.println(" V");

	Serial.print("Battery percent: ");
	Serial.print(batteryPcnt);
	Serial.println(" %");
#endif

	if (oldBatteryPcnt != batteryPcnt) {
		// Power up radio after sleep
		sendBatteryLevel(batteryPcnt);
		oldBatteryPcnt = batteryPcnt;
	}
	sleep(SLEEP_TIME);
}

Thanks

@TimO ,
Thanks for the reply.

OK So if I can use a mixture of either self discovery and files thats fine BUT as soon as I un-comment the sensors in mysensors.items the thing sensors double up in Openhab? See below?

Openhab discovered the highlighted sensors (only after I reset the sensor node!) and then when I ticked the discovered sensors it added the extra two sensors not highlighted?!? Weird as I have only one DHT11 sensor... Any ideas whats going on?

I started out this evening by deleting the sensors and the gateway in openhab, restarted openhab. I then added the gateway, reset the node which added the 4 things.
Now I am getting data on the sitemap for the first time! Eh.....
Should I have each sensor doubled up then? and I didnt link any channels either....

Now I am confused...

@pavel-hrudka I know this is quite an old post but I discovered tonight that when openHAB would not discover my node, I hit reset on the node and openHAB discovered the sensor when it restarted and contacted the GW. May help someone in the future!

This is my first post so hello to everyone, I have been a lurker for some time and have just setup my first ethernet GW with a DHT11 sensor on a node. Both running on Arduino uno clones. I have an existing Openhab setup thats been running for a couple of years now but decided there were a lot of Mysensor projects that I wanted to try!
Although I have the GW setup with the Node and they are talking to each other, and Openhab discovered both the temp and humidity sensor, I can not get the data to display on my sitemap. So I have a few questions-:

1. Do I need to have a manual things file as below?
   

2. Do I need to specify in the Arduino sketch a Node ID as below or does openhab assign them?
   

Below are my .items , sitemap and openhab thing screenshot. Has anyone done a recent Openhab 2.4 install with an ethernet gateway that can see any mistakes?

Hope someone can help, I am so close but not quite there.... I am no programmer so go easy on me!