Mushroom Environment Control - Arduino Powered

Step 3 Humidity Reader

The humidity sensor is a variable capacitor which changes linearly with the relative humidity.
The datasheet shows how to hook up the sensor using a 555 timer (must use CMOS type).
I used this circuit to send data pulses to the Arduino. At first I found the pulses were too close together and did not give high enough discrimination, so at the output of the 555 I put a digital divide by ten chip. This made it so the pulses wavelength was in the hundreds of microseconds rather than the tens of microseconds. 
Please find attached the datasheet which has the circuit diagram using the 555 timer.

I used the same style inline screws as described with the Thermistor step as a go between for this sensor and the Arduino.

To Test this, hook up the output to a speaker supply power (6volts will do) and breath on the sensor, you should hear a drop in frequency.

Comments

[jbark]

Hi Anthony,

I'm new to electronic. I got my self cd4017 for the divider, can you please tell me where you the output from 555 goes to? Or how do I know which one divides. This one is tricky to follow.
By the way this is my very first electronic that's not a kit from Jaycar. I'm almost there with it but this one has got me stuck.

So I followed your instruction.

Cheers

Thanks

[anthony_p1234]

Hi Jbark,

Sorry, I didn't put much detail in about that. But basically it's something like this:
http://artengine.ca/~pflemming/flemmweb_current/schem/CMOS/4017_circuits.pdf
555 Timer --> pin 14 of cd4017. Then output of cd4017 pin 11 to arduino. Ground pin 8, 13 and 5.

Thanks
Anthony

[ricbordenave]

Sorry... Ground are pins 8, 13 and 15. Thanks

[jbark]

Thanks Mate