3 replies to this topic

[JimmyNet]

Hallo All, I am trying to connect the Humidity sensor GY-HR002. First pin goes to the 3.3v supply. Second pin goes to the analog port / pin 5. In the specs of Humidity sensor GY-HR002 it requires a voltage of 1.5 volt AC see specs: http://www.produktin...OR_GY_HR002.pdf My quistions: 1. Is my wiring ok? 2. Is the voltage ok or do have to use a resistor? 3. can i use the 3.3 dc volt or is has to be AC? Am i overlooking some issues? I added the specs as a attachment. Gr. jimmy

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[baxter]

Here is a recent discussion of humidity sensors on the Picaxe forum, http://www.picaxefor...umidity-sensors It seems they are not so easy to deal with. Baxter

[Paul Newton]

Hi Jimmy Sorry but you can't use it in a simple circuit with DC. You need an alternating voltage of 1.5V. (The datasheet says you can use a square wave.) You also need to measure the temperature; you have to compensate the reading to allow for the ambient temperature. I didn't find any example circuits. I expect the proper way to use it is as an element in an oscillator such that the humidity causes the frequency of the oscillator to change. That then gives the problem of needing to measure the frequency that is generated. It might be possible to get a rough circuit working by using it as part of a potential divider: Connect the sensor in series with a fixed resistor to form a potential divider. Use a PWM output to generate a 50% duty cycle square wave. Drive one end of the divider with the PWM signal and join the other end to approximately 1.6V. Then rectify and smooth the voltage at the centre of the divider into a variable DC voltage so it can be measured by an analogue input. This would take a lot of trial and error - I don't hold much faith that this will give a usable result. Paul

[JimmyNet]

Hallo Paul and Baxter, Thank you for your reply. It is clear that is not that easy as i was thinking. At least i learned now more about reading specs. I will use the Humidity and Temperature Sensor - RHT03 instead. Regards Jimmy.