The RHT03 is a digital humidity sensor. It is sometimes know as the DHT22. The sensor is available from Sparkfun here.

Wiring the RHT03¶

The sensor comes in a 4 legged package, but only 3 are required. The pins are numbered 1-4 from left to right when looking at the front of the sensor.

Powering the sensor¶

The will work on any voltage from 3.3-6v. The datasheet advises putting a 100nF capacitor between VDD and GND for wave filtering, but don't worry if you don't have one of these it will still work!

VDD should be connected onto pin 1 and GND onto pin 4.

Data Line¶

The sensor uses a MaxDetect 1-wire bus, this is a dual direction digital signal. This can be connected to any of the Digital In/Out ports on the mbed. The digital in/out port of the mbed should be connected to pin 2 on the RHT03. A 1K pull up resistor is also required on the data line.

Wiring Diagram¶

Getting Data from the RHT03¶

The bus/sensor is a little bit temperamental at times...

All you need to know about getting the data is:

• You have to wait at least 2 seconds after a power on to get data from the sensor
• You can only request data from the sensor every 2 seconds
• You will get a get a couple of check sum errors most times you try to read sensor data

RHT03 Library¶

RHT03 Test program¶

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Useful Links¶

Data sheet: http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Sensors/Weather/RHT03.pdf