I2C

Projects Programming
1

Hi.

The DHT11 Temperature and Humidity sensor, in my self built weather station as somehow failed, instead of a direct replacement i have decided on a small upgrade.

I am using an Arduino UNO R3 Board, i have decide i would like to us a BME280 in my weather station instead of a DHT11, the problem i have is i already have 2, i2c sensors on my board, a 20,4 LCD and and a BH1750 light sensor. My question is this, would it be better to parallel connect all 3 sensors, or simple connect my new sensor in parallel with one of the original sensors?

2

You should connect all 3 sensors on the same I2C bus. Just make sure that all the sensors have different I2C addresses.

3

The Arduino Uno is a 5V board.
The LCD with I2C backpack uses a 5V I2C bus.
The BH1750 is a 3.3V sensor.
The BME280 is a 3.3V sensor.

How are you going to connect that ? Do the BME280 and BH1750 modules have level shifters for SDA and SCL ?

4

Koepel:
The Arduino Uno is a 5V board.
The LCD with I2C backpack uses a 5V I2C bus.
The BH1750 is a 3.3V sensor.
The BME280 is a 3.3V sensor.

How are you going to connect that ? Do the BME280 and BH1750 modules have level shifters for SDA and SCL ?

Yes I forgot about that because I don't know these sensors.

You should use a 5V - 3.3V logic level shifter.
If you don't do so, then your sensors might get damaged.

5

When we talk about BME280 sensor, we usually refer to this BME280ModuleLevelSifter.jpg sensor module which contains 5V/3.3V/5V level sifters (at the other sidea) and it can be directly connected with the I2C Bus of UNO.

This BME280 Module bme280EWithoutLevelSifter.png does not contain level sifter.

BME280ModuleLevelSifter.jpg

bme280EWithoutLevelSifter.png

6

Given the time and effort it took to get this working originally, I'd personally be inclined to just get a replacement sensor. If you fancy the challenge though, I'm sure folks here will help get it working.

7

Many Thanks for the info.

I am using the 4 pin BME280/BMP280 sensor, secs at 3.3 > 5 v

The BH1750 sensor specs at 3.3 > 6 v, so i do not need shifters , i believe.

8

Can you give links to the BH1750 and BME280 modules that you have. Preferably, a link to where you bought it.

The specifications are in the datasheets. The bare sensors are for 3.3V.