ESP8266 with Dallas DS18B20 temperature sensor


This project uses the History Graph widget, which I believe has been superseded by the SuperChart, but anyway:


Thank you :wink: I’m a noobie dealing with blynk and your project is a good example how it should be done :slight_smile:


I just wanted to say thanks for posting this - I’ve had Blynk, an ESP12e and a ds18b20 sitting around for a couple years wanting to do this exact thing…but never had the time to work on it. Now I’m up and running! I’m going to use this for making some freezer temp monitors. Thanks for sharing!


How can i add more sensors ?? Need at least 3 sensors…


@Mauricio_Lima, Are you asking about the hardware or the software?

For the hardware, additional sensors can be added in parallel on the same wire. (That’s why the interface is called “1-Wire”.)

For the software, the startSensorRead() function already starts the conversion for all sensors connected to the bus, so no changes are required there.

You would have to expand and modify the sensorRead() function to read all the sensors, instead of just one, and add virtual pins for them. If you put the sensor device addresses in an array, you could use a loop and index to read them.

The initialisation for more than one sensor will have to be performed in setup(), as well. Essentially, anywhere where the tempSensor variable containing the device address is used.

What you have to consider is how to handle monitoring, alerts and errors for more than one sensor. Do you want separate maximum and minimum temperature tracking, and max/min alerts and notifications, for each sensor? What happens when one or more sensors fail but the others remain working, in terms of flashing the LED for status indication?


Very nice and complete presentation of your project! :+1:

Since I’m a self proclaimed DS18B20 wrangler :nerd_face: I have some input that might speed things up, even if not necessary :slight_smile:

// The number of bits of temperature resolution
// 9 = 0.5, 10 = 0.25, 11 = 0.125, 12 = 0.0625 degrees Celsius

// Temperature conversion wait time, in milliseconds
#define READ_CONV_WAIT 800

// We'll do the "wait for conversion" ourselves using a timer,
// to avoid the call to delay() that the library would use

The conversation time with 10 bit resolution is only 187.5 ms, so no need to wait for 800 ms. You don’t even have to wait for the 187.5 ms if you don’t want to. You could execute other code and come back after ~200 ms and just read the result of the conversation, which only takes about 30 ms.

I’m using two timers in my project to do this “hit-n-run” on the sensors :slight_smile:

@Mauricio_Lima There is examples of how to use multiple sensors hidden somewhere in the forum. I can’t remember where so you have to search for your self :slight_smile:


Each sensor can be accessed in one of two ways…

  1. Via its internal address (I recall finding some program that read the address of each sensor… Google for that)

This OPs project uses that method… eg.

// Temperature sensor full ID, including family code and CRC
DeviceAddress tempSensor = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 };
  1. Via the index… which is basically the placement order on the bus… I think.

I have used this to test read the value of multiple (5) sensors at once.

void getTempData()

  Blynk.virtualWrite(V45, DS18B20.getTempCByIndex(0));
  Blynk.virtualWrite(V46, DS18B20.getTempCByIndex(1));
  Blynk.virtualWrite(V51, DS18B20.getTempCByIndex(2));
  Blynk.virtualWrite(V52, DS18B20.getTempCByIndex(3));
  Blynk.virtualWrite(V53, DS18B20.getTempCByIndex(4));

As mentioned… search this forum (and Google) for other projects and how they do it.


My dear antagonist @Gunner, why the delay?

void getTempData()

Unless waitForConversion is set to false, the requestTemperatures() returns when the conversion is good ready :slight_smile:

BTW, the sensor has a built in alarm function and supported in the standard DallasTemperature-library. Perhaps that’s something to implement in a distant future :smiley:

Flexible User-Definable Nonvolatile (NV) Alarm Settings with Alarm Search Command Identifies Devices with Temperatures Outside Programmed Limits


Antagonist… who, me :innocent: Actually I wasn’t paying attention when I posted that, so no, I wasn’t trying to undermine your much better implemented methods, just showing the index method.

It was just test code and not meant for any active project.

Hmmm, good to know… I think I needed to add the delay, way back when, because as I added more sensors I noticed that the return value was the error -127 without the delay. I can’t remember what I had in the setup.


Woups, turns I did still have that code in an active project (and no waitForConversion() command anywhere :thinking:)… but it was set for a manual button reading.

So I changed it to this, and it works just fine without the delay. Not that I could notice a quarter second delay on a manually called reading anyhow :stuck_out_tongue:


Thanks for the knowledgeable info @distans (seriously). I always knew you were full of something :smile: JK - the antagonist in me escaped briefly :wink:


You don’t have to set it and default is true afaik. Therefore the use of that function is easily overlooked or even notice its existence. In many standalone applications, some delays here and there isn’t that crucial for the overall performance. But with Blynk there is always the heartbeat/connection issues to consider. But you know all that already.

I’m just trying to give others some pointers and learn from my mistakes.

CAREFUL!!! :joy:


Yes, I know that, but I only read the sensor every 30 seconds anyway. By using an “absolutely safe in all cases” 800ms, I don’t have to worry about forgetting to change it if I were to increase the resolution in the future. There’s no down side to a long delay. The sensor isn’t going to “forget” the reading any time after it’s been acquired.


I’m not saying you’re doing it wrong, just that there is another way to do it :laughing: Don’t take it as criticism, I think this is one of the best presented, complete and easy to follow projects I’ve seen here :+1: But I’ve grown allergic to unnecessary delays when working with Blynk and it all started with those 800 ms the temp sensors gave me :smiley:

With my sometimes shaky 4G/LTE internet, the delays made me loose the connection to the Blynk cloud from time to time so I needed to write “better” code to avoid it. Today I’m using a local server so I probably wouldn’t have that problem now.

I’ve never heard of a DS18B20 to fail due to too many EEPROM writes but bear in mind that they “only” guarantee 50.000 writes. Twice a minute makes 2880 writes per day and after just 2,5 weeks you hit that 50k mark!

How long have you been running this project? Would be interesting to know if or when they actually start to fail :face_with_monocle:


I didn’t, and my response was only intended to inform you that I was aware that a shorter acquisition wait time could be used, and to give my reason for making it a bit longer than required.

I don’t use a delay. I use a timer. is called continually while the acquisition wait timer is waiting to time out. I could make the timeout 20 seconds and the sketch would still run fine (other than the time stamp, that the server records for each reading, being 20 seconds later than when the reading was actually taken).

My code doesn’t write to any EEPROM in either the sensor or the ESP8266. I only read from the sensor and send the results to the Blynk server, so nothing is being “worn out”.


Ahh… misunderstood your code. Sorry! :slight_smile:

But but… You do!?

Reading the datasheet again to see if I misunderstood even more!


It seems like the motherloving scratchpad is actually SRAM, not EEPROM! :astonished:

The DS18B20’s memory is organized as shown in Figure 9. The memory consists of an SRAM scratchpad with nonvolatile EEPROM storage for the high and low alarm trigger registers (TH and TL) and configuration register.

I can either retract one gazillion posts and forever be in shame, or pretend like nothing has happened and silently delete my account! :rage: Well… It’s been nice knowing y’all !

@MLXXXp - thanks for setting me straight! :slight_smile:


Account deleted as requested :stuck_out_tongue_winking_eye:


I’ve updated my project to use the SuperChart instead of the now deprecated History Graph. I also changed the temperature read interval from 30 to 60 seconds.


Hi! great work! I’m new with arduino and blynk, I’m trying to test this code with a Wemos D1 R2, for the moment I’ve tryed to put my token and my wifi ssd and pass, also I’ve changed the DS18B20 pin to D4 pin. The DS18B20 it’s workin cause I’ve already tryed on a arduino mega.
The issue is that I cant get to connect Wemos with Blynk using this code. I’ve tryed with an example and it works, do you have any idea what i’m doing wrong?

greetings from Argentina!


It’s difficult to tell what your problem is with the information you’ve provided.

What can’t you get to connect? The Wemos to the Blynk server? The Wemos to the DS18B20?

If you can’t connect to the DS18B20, make sure you enter the device ID for the sensor you’re using. Every DS18B20 has a unique ID. The values I’ve provided are just “dummy” values and won’t work for any real DS18B20.

// Temperature sensor full ID, including family code and CRC
DeviceAddress tempSensor = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 };