{"id":1476,"date":"2018-09-22T13:00:04","date_gmt":"2018-09-22T12:00:04","guid":{"rendered":"http:\/\/chewett.co.uk\/blog\/?p=1476"},"modified":"2018-09-24T20:08:23","modified_gmt":"2018-09-24T19:08:23","slug":"using-the-dht22-temperature-sensor-with-a-wemos-d1-mini-esp8266","status":"publish","type":"post","link":"https:\/\/chewett.co.uk\/blog\/1476\/using-the-dht22-temperature-sensor-with-a-wemos-d1-mini-esp8266\/","title":{"rendered":"Using the DHT22 Temperature Sensor with a WeMos D1 Mini (ESP8266)"},"content":{"rendered":"

\"\"<\/p>\n

In this blog post I talk about the additional steps needed to use the DHT22 temperature sensor with a WeMos D1 Mini (ESP8266) with the Arduino IDE.<\/p>\n

<\/p>\n

Differences from running a DHT22 on an Arduino<\/h2>\n

There are two major differences to bear in mind when using the DHT22 on a Wemos D1 Mini (ESP8266) or similar chipset.<\/p>\n

The primary difference when using the Arduino IDE with the WeMos chips is that the standard pin numbers do not refer to the pin numbers on the WeMos. For example, instead of using 1<\/code> to refer to digital pin 1<\/code>, you need to use the constant D1<\/code>.<\/p>\n

I go into more details for this in my blog post\u00a0Pin numbering for WeMos D1 Mini (ESP8266)<\/a>. If you haven\u2019t read this and are having trouble connecting your DHT22 properly I recommend having a read.<\/p>\n

The second and more problematic issue is that the standard DHT22 library does not work with the WeMos. After some work looking into this I found that this was because the ESP8266 runs much faster than the Arduino. Since the DHT library has quite strict timing requirements this means that it fails to work correctly.<\/p>\n

However there is a\u00a0\u201cDHT sensor library for ESPx\u201d by beegee_tokyo which works well.<\/p>\n

Wiring it up to a WeMos D1 Mini<\/h2>\n

\"\"<\/p>\n

Here I am connecting the DHT22 sensor to a WeMos D1 mini. To more easily connect the sensor I have connected the 3.3 volt and GND lines to the breadboards + and – lines respectively.<\/p>\n

In the diagram I am showing the four pin version of the DHT22. To more easily show the sensor diagram I have reversed the DHT22 sensor. The pins left to right are VCC (show on the right on the diagram), Data, not connected (not present in the 3 pin version), and GND (shown on the left on the diagram).<\/p>\n

It is important to note that the WeMos’s digital pins can only accept up to 3.3 volts maximum on their inputs. This means that the DHT22 sensors VCC pin must be connected to the 3.3 volts and not the 5 volt line.<\/p>\n

The data pin is connected to D2 on the WeMos. This is also connected to a 10k resistor between the data pin and the 3.3 volt line on the breadboard. This pull-up resistor ensures that the line is pulled up when floating.<\/p>\n

Programming the Wemos with the DHT22<\/h2>\n

Here instead of using the standard DHT library I am using DHTesp. This library built specifically to use DHT devices on ESP8266 microcontrollers.<\/p>\n

I was able to use this library to log the temperature and humidity and print it out on the serial connection.<\/p>\n

#include "DHTesp.h"\r\nDHTesp dht;\r\n\r\nvoid setup() {\r\n    Serial.begin(115200);\r\n    dht.setup(D2, DHTesp::DHT22);\r\n}\r\n\r\nvoid loop() {\r\n    float h = dht.getHumidity();\r\n    float t = dht.getTemperature();\r\n\r\n    Serial.print("{\\"humidity\\": ");\r\n    Serial.print(h);\r\n    Serial.print(", \\"temp\\": ");\r\n    Serial.print(t);\r\n    Serial.print("}\\n");\r\n\r\n    delay(2000);\r\n}<\/pre>\n
The\u00a0DHTesp::DHT22<\/code>\u00a0constant is used in the setup function to tell configure the\u00a0dht<\/code>\u00a0variable to talk to the sensor using the DHT22 protocol.<\/p>\n
Summary<\/h2>\n
The DHT22 sensor is a really nice sensor to measure temperature and humidity that can be used with the WeMos D1 mini. Although there\u00a0 is some complication as the standard DHT22 library cannot be used there is a library designed for the ESP8266 chipset such as the WeMos D1 mini.<\/p>\n
For a full review of the DHT22 have\u00a0a read of my previous post<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"
In this blog post I talk about the additional steps needed to use the DHT22 temperature sensor with a WeMos D1 Mini (ESP8266) with the Arduino IDE.<\/p>\n","protected":false},"author":1,"featured_media":1545,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"Over the weekend I wrote about using the #DHT22 Temperature #Sensor with a #WeMos D1 Mini (ESP8266)","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[97],"tags":[211,145,293,180,152,179,209,208],"class_list":["post-1476","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-electronics","tag-arduino-ide","tag-dht22","tag-dht22-temperature-sensor","tag-humidity-sensor","tag-sensor","tag-temperature-sensor","tag-wemos","tag-wemos-d1-mini-pro"],"wppr_data":{"cwp_meta_box_check":"No"},"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/chewett.co.uk\/blog\/wp-content\/uploads\/2018\/09\/dht22_on_wemos_d1_mini.jpg?fit=800%2C800&ssl=1","jetpack_shortlink":"https:\/\/wp.me\/p2toWX-nO","jetpack_sharing_enabled":true,"jetpack-related-posts":[{"id":1412,"url":"https:\/\/chewett.co.uk\/blog\/1412\/using-the-ds18b20-temperature-sensor-with-a-wemos-d1-mini-esp8266\/","url_meta":{"origin":1476,"position":0},"title":"Using the DS18B20 Temperature Sensor with a WeMos D1 Mini (ESP8266)","author":"Chewett","date":"November 21, 2018","format":false,"excerpt":"In this blog post I talk about the additional steps needed to use the DS18B20 onewire temperature sensor with a WeMos D1 Mini (ESP8266) using the Arduino IDE. Important differences compared to using the DS18B20 on an Arduino There is one major difference to bear in mind when using the\u2026","rel":"","context":"In "Electronics"","block_context":{"text":"Electronics","link":"https:\/\/chewett.co.uk\/blog\/category\/electronics\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/chewett.co.uk\/blog\/wp-content\/uploads\/2018\/11\/wd18b20_on_wemos_d1_mini.jpg?fit=800%2C800&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/chewett.co.uk\/blog\/wp-content\/uploads\/2018\/11\/wd18b20_on_wemos_d1_mini.jpg?fit=800%2C800&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/chewett.co.uk\/blog\/wp-content\/uploads\/2018\/11\/wd18b20_on_wemos_d1_mini.jpg?fit=800%2C800&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/chewett.co.uk\/blog\/wp-content\/uploads\/2018\/11\/wd18b20_on_wemos_d1_mini.jpg?fit=800%2C800&ssl=1&resize=700%2C400 2x"},"classes":[]},{"id":1405,"url":"https:\/\/chewett.co.uk\/blog\/1405\/using-the-dht11-temperature-sensor-with-a-wemos-d1-mini-esp8266\/","url_meta":{"origin":1476,"position":1},"title":"Using the DHT11 Temperature Sensor with a WeMos D1 Mini (ESP8266)","author":"Chewett","date":"August 18, 2018","format":false,"excerpt":"In this blog post I talk about the additional steps needed to use the DHT11 temperature sensor with a WeMos D1 Mini (ESP8266) with the Arduino IDE. Differences from running a DHT11 on an Arduino There are two major differences to bear in mind when using the DHT11 on a\u2026","rel":"","context":"In "Electronics"","block_context":{"text":"Electronics","link":"https:\/\/chewett.co.uk\/blog\/category\/electronics\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/chewett.co.uk\/blog\/wp-content\/uploads\/2018\/08\/dht11_on_wemos_d1_mini.jpg?fit=800%2C800&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/chewett.co.uk\/blog\/wp-content\/uploads\/2018\/08\/dht11_on_wemos_d1_mini.jpg?fit=800%2C800&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/chewett.co.uk\/blog\/wp-content\/uploads\/2018\/08\/dht11_on_wemos_d1_mini.jpg?fit=800%2C800&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/chewett.co.uk\/blog\/wp-content\/uploads\/2018\/08\/dht11_on_wemos_d1_mini.jpg?fit=800%2C800&ssl=1&resize=700%2C400 2x"},"classes":[]},{"id":1854,"url":"https:\/\/chewett.co.uk\/blog\/1854\/using-the-801s-wide-range-vibration-detection-sensor-with-a-wemos-d1-mini-esp8266\/","url_meta":{"origin":1476,"position":2},"title":"Using the 801S Wide Range Vibration Detection Sensor with a WeMos D1 Mini (ESP8266)","author":"Chewett","date":"March 9, 2019","format":false,"excerpt":"In this blog post I talk about how you can use a 801S Wide Range Vibration Detection sensor with a WeMos D1 Mini (ESP8266) using the Arduino IDE. Summary of the\u00a0801S Wide Range Vibration Detection sensor This vibration sensor works by the sensor changing resistance as motion is detected. 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Summary of the SW-420 Motion Vibration Sensor This sensor mounts a motion detection component with a small micro-controller and a potentiometer. 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Summary of the TTP223B Capacitive Touch Sensor The TTP223B capacitive touch sensor works as a standard button. 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