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build an IOT gadget with Blynk

Q&A Forum › Category: ESP8266 › build an IOT gadget with Blynk
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Larry asked 2 years ago

So I completed the project , was a bit confusing seeing how what you show for the app as far as setting go is different from the actual app. My question is , why don’t I get the right values from the DHT11? Temperature seems close but the humidity is showing 89% even though its 46%.I know this from other sensors placed next to it, also my Serial window shows Failed to read DHT sensor but in fact it is reading it. Your print shows the DHT11 with 4 pins, mine is a DHT with 3 pins, I am led to believe it has the resistor built in so I am not using a resistor in my circuit.Just as a note, I swapped out the sensor with another that was working in another project and still does’t read correctly.Thanks, hope to get an answer soon on this.

Question Tags: home automation
18 Answers
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Sara Santos Staff answered 2 years ago

Hi Larry.
If you have the 3-pin version you don’t need to connect the resistor.
Which voltage are you supplying to the VCC pin?
When there is a big humidity value, it will take some time for it to drop. Imagine that you blew to the sensor to see how it changes. It will take some time to get the humidity down.
It may also be the case that the DHT is very badly calibrated for the humidity values.
Can you try using a default DHT example for the ESP8266, like this one and see if it works: https://github.com/adafruit/DHT-sensor-library/blob/master/examples/DHTtester/DHTtester.ino
Regards,
Sara 

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Larry answered 2 years ago

Ok so I tried the other file , I believe it loaded DHT_U.h and same results, will let it sit for awhile but not much hope, also tried using 3 v but that didn’t change. To answer your question I first used vin which I believe should be  5v, also still get failed to read from DHT sensor

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Larry answered 2 years ago

     Sara, sorry for the confusion here on my part, I loaded the test program you said to use and I get the same result, failed to read sensor on the Serial monitor. Confused by some of the instruction, when it says DHT pin 2 I am assuming it wants D2 or is it looking for a GPIO pin? 
I have used this same DHT11 on other projects you have here and it always worked so I am really having a hard time thinking that it is a sensor issue.Thanks

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Sara Santos Staff answered 2 years ago

Hi Larry.
You should connect the data pin to GPIO 2. GPIO 2 is marked on the board as D4.
Try it with the right GPIO and let me know if it solves the issue.
Regards,
Sara

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Larry answered 2 years ago

So I tried what you suggested and the tester program works , it reads the DHT11 . If I swap it out with a different sensor. Confusing here because both of my DHT sensor work on a different project. Haven’t tried it on the lesson program but will do and I assume it will work, will let you know. Thanks

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Larry answered 2 years ago

So I am logged in and it tells me I don’t have access to this unit. “Build an IoT Gadget with Blynk app and ESP8266”. So why don’t I have access when I was here before. Not having fun here.

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Larry answered 2 years ago

So I am logged in and it tells me I don’t have access to this unit. “Build an IoT Gadget with Blynk app and ESP8266”. So why don’t I have access when I was here before. Not having fun here.Also Blynk app still shows humidity at 89%.

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Sara Santos Staff answered 2 years ago

Hi Larry.
I’m sorry for the misunderstanding. You can access the units here: https://rntlab.com/module-unassigned/build-an-iot-gadget-with-the-blynk-app-and-esp8266/
See Rui’s response: https://rntlab.com/question/build-an-iot-gadget-with-blynk-3/
If your sensor still shows 89%, it may be not working properly.
Did you solved the other issues related with the sensor?
Regards,
Sara

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Larry answered 2 years ago

Sara
Ok so I used your link and got the same message that I don’t have access to that unit. 
Rui
to answer your question, one of my sensors works, it reads better but still way off. Confused because both sensors work on a different project and only one works but not accurate ,and very unstable. 

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Larry answered 2 years ago

Just curious, how does the Green Led work, it never turns on?

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Rui Santos Staff answered 2 years ago

Thanks for letting me know Larry! I’ve fixed your course access permissions and you can access it at:

  • https://rntlab.com/module-unassigned/build-an-iot-gadget-with-the-blynk-app-and-esp8266/
  • https://rntlab.com/module-unassigned/extra-installing-the-esp8266-board-in-arduino-ide/

I wasn’t aware that our Blynk project was outdated, so we’ve decided to temporarily remove it while we work on updating it. I don’t recommend following it right now.

These inexpensive sensors sometimes are a bit faulty or they might be damaged. Can you try with a different sensor (do you have multiple sensors)? You might also consider using a DHT22 since it’s more accurate.

As I said, the project is currently outdated and we need to re-test why the green led is not working as expected.

Regards,

Rui

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Larry answered 2 years ago

Thanks, link now working, as far as more sensors, I ordered 2 at Banggood but it’s been several weeks now and still haven’t seen anything. I do have 2 different DHT 11 and both of them work well on other projects but only 1 works on the Blynk app and it’s not very close to being right. The other doesn’t work at all not seen  on the Blynk project. As I said they both work on another project correctly, adds to my confusion/ frustration. 

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Rui Santos Staff answered 2 years ago

During this season, there are so many online orders that the postal service is overwhelmed… Everything is very delayed in Portugal too.
That’s quite weird and I honestly can’t give you a good answer on why that happens, because I’ve never experienced that behavior before.

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Larry answered 2 years ago

     Ok thanks for your quick response,  I appreciate your answer as always. I am having much difficulty with your courses because of the coding. The way you are instructions don’t seem to really get into teaching, more cut and paste and light on actual instruction, at least for me .

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Rui Santos Staff answered 2 years ago

Hello again and I apologize for taking so long to get back to you!

I really apologize for this issue using the Blynk app with our project. Unfortunately we try to focus more on building projects with a practical teaching approach, I can offer you a full refund if you’re not happy.

No hard feelings, it’s up to you… 🙂

Regards,
Rui

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Larry answered 2 years ago

No I think your approach has value to many others , I may just be too inexperienced to gain much at this point but do enjoy the projects. I was hoping for a more basic and instructive course. I have little to no experience here, I understand logic and cut my teeth on relay logic . I have an electrical back ground as a licensed master electrician, not any engineering. I will keep going, sooner or later I may pick up some knowledge, I assumed this would be a course to learn as a start not some one with experience or engineering. 

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Larry answered 2 years ago

Thanks

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Rui Santos Staff answered 2 years ago

I understand and we are always looking for feedback in order to improve our guides and eBooks. All your feedback it valuable, thank you for your time.
I wish you a happy new year and feel free to post any new questions! I hope I can help better next time.

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