The DHT11 Digital Humidity Sensor is available on Ebay and elsewhere and is an inexpensive alternative to sensors from Honeywell, Sensirion and Humirel. This project shows how to make this Sensor work with a Picaxe X2.
I had received several of these for testing but was unable to get them working due to a speed / timing issue related
to Picaxe processing overhead. But thanks to a clever workaround by Picaxe Forum Member MGU (Maguin Michel - Paris France ) the problem was solved. I took his idea and built a working circuit using a 74Hc221 instead of the 555 timer.
The results look very good and the Humidity and Temperature outputs are stable & accurate enough for many applications.
The DHT11 Datasheet can be found here:
http://www.robotshop.com/PDF/dht11.pdf
http://www.micro4you...ensor/DHT11.pdf
This is how I did it. ( See the Attached Files)
Edit: Added Schematic for using 555 timer instead of 74HC221. Fixed Graphic
I had received several of these for testing but was unable to get them working due to a speed / timing issue related
to Picaxe processing overhead. But thanks to a clever workaround by Picaxe Forum Member MGU (Maguin Michel - Paris France ) the problem was solved. I took his idea and built a working circuit using a 74Hc221 instead of the 555 timer.
The results look very good and the Humidity and Temperature outputs are stable & accurate enough for many applications.
The DHT11 Datasheet can be found here:
http://www.robotshop.com/PDF/dht11.pdf
http://www.micro4you...ensor/DHT11.pdf
This is how I did it. ( See the Attached Files)
Edit: Added Schematic for using 555 timer instead of 74HC221. Fixed Graphic
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