Humidity Sensor

Hello

I am trying to design a humidity sensor circuit and i have found the following circuit for the humidity sensor HS1101.


The design was taken from eh data sheet for the HS1101
https://www.parallax.com/Portals/0/Downloads/docs/prod/sens/27920_HS1101-Datasheet.pdf

My problem is that i would like to connect it to a display so it can tell me now much humidity has been detected in the air.

Could someone please help me with this.

Thank you in advance

Hi, at what stage have you setup the circuit? Have you configured the capacitance-to-voltage conversion?

Vizier87

you will get a frequency out, so you'll either need a tachometer chip for an analog (meter) type display, or a frequency counter circuit, but you want to display RH (relative Humidity), then you'll have to convert the frequency to humidity. Probably using a micro. (most would say PIC, I say ATMEL!!!)

You can make up a simple circuit to measure frequency with a analogue or digital meter, do a google for analogue frequency counter.
If you were to use a pic (sorry mike) then you wouldnt use a 555, you'd use the pic's comparator as an oscillator with the sensor as the capacitive element.
Then again if yoiu use a micro then you'd use something like a dht11 temp/humid sensor that has a built in digital interface.

unless, you don't want to pay the higher price for the built in digital interface, since you've got your micro already and it's cheaper to do the interface yourself... I once did a board for an engineer that I put amps on the board even though the family of sensors had built in amps... he wanted to use the cheaper version, and why pay someone else to build something you can build for yourself cheaper, unless you want it to be easier (lazy *******)...

but one good thing about the built in interface, they're usually calibrated... and yes, I know you're sorry for using a PIC...

Actually in this instance using a digital sensor would be cheaper (like the pic), dht's are around 3 quid, discrete sensors are double or triple.
That said the essence of what you say is quite right, except avr's.