Humidit sensor circuit (using HIH4000)

[santais]

Hi There.

I'm currently working on an exam, where I'm making a humidity sensor with a diode as an inidicator when the RH % hits a certain percentage.

I originally attended to use a HS1101 with a condenser, where I could position a potientmeter, so i.e. when the RH is at 50%, a red diode would up. But the school forgot to buy some of the HS1101, so I'm stuck with the HIH4000.

My knowledge within electronics isn't that great. So the main question is, do you have any suggestions for a possible circuit? I've been looking around the internet, but can't seem to find with the HIH4000 in. The circuit I actually had in mind of making sounds something like this:

Condensator to an amplifier and controlled by a potientmeter. If the RH% s high enough, there will be a HIGH on the electricity and it would flow through a transistor and make one of the diodes ligh(red). If the eletricity is low, i would go through another circuit and again through a transistor and make another diode light(green). But I don't now how much of this is still possible to make?

I don't know if I'm to link other links on this site, but the one I used for this original humidity sensor can be found if you search on"humidity sensor circuit) and it's the simple circuit with a yellow backgruond using a HS 1101 in the stat.

On beforehand tank.

 

[ericgibbs]

hi,
I have attached the HIH4000 datasheet.
The IC you require is a Comparator, the LM393 IC is an example of this type.

 

[santais]

Thanks

So I changed it a bit. It now runs through a comparater (LM358 - it was the closest to LM393 I could find) and continues to a diode. The main VCC is at 5V and runs through a resistor at 180 ohm and 120 ohm whichshuld decrease the VCC to 2V. Is it possible then, to se another power source, i.e. higher than 2V (it can variate of course) at the - input in the comparater to make a fake humidity sensor input? I tried it so far, but the diode keeps lightning, no matter if I change it to 5 V or higher, it keeps lightning. It should work in theory, but do you have any suggestions, would could cause the error? If I can this circuit to work, then I can simply just copy/paste it and change the V output on the second comparator to match the RH % for the output.

 

[ericgibbs]

Thanks

So I changed it a bit. It now runs through a comparater (LM358 - it was the closest to LM393 I could find) and continues to a diode. The main VCC is at 5V and runs through a resistor at 180 ohm and 120 ohm whichshuld decrease the VCC to 2V. Is it possible then, to se another power source, i.e. higher than 2V (it can variate of course) at the - input in the comparater to make a fake humidity sensor input? I tried it so far, but the diode keeps lightning, no matter if I change it to 5 V or higher, it keeps lightning. It should work in theory, but do you have any suggestions, would could cause the error? If I can this circuit to work, then I can simply just copy/paste it and change the V output on the second comparator to match the RH % for the output.

hi,
The LM358 is really an OPA operational amplifier, but can be used a comparator.
Its not a good idea to decrease the Vcc supply to an amp using 2 resistors.
I will draw a simple circuit and post it later.

 

[santais]

Thanks Ericgibbs.

Yeah that kinda shows how much I know within the electronic world, but you need to learn it somehow .

And thanks for drawing a circuit for me. I'm looking forward to it

 

[ericgibbs]

Thanks Ericgibbs.

Yeah that kinda shows how much I know within the electronic world, but you need to learn it somehow .

And thanks for drawing a circuit for me. I'm looking forward to it

hi,
Look at this LTspice simulation.
The LM358 is powered from +5V [ideally it should be Vcc=8v to give a 5Voutput]
The LM358 output will go high, about +3.5V when the HIH output is at 50% [+2.5v] and higher.

I have have drawn a simple variable resistor test circuit on the left side so that you can test the LM358 when the HIH is NOT connected.
Any questions, please ask.

 

[santais]

Thanks a lot for the help.

I helped a lot with the circuit drow. Got it somehow working now. The green diode lighs untill it reaches a V on 2. I havn't tried the red diode yet, which turns on at 2,5 V. I am having trouble getting so much moisture in the air But I also made a yellow diode, using a NAND gate, that turns on while both the green and red diode is turned off. Having some problems with that, since the output is on high, while either of the diodes is on, where it should be low. But shuold be possible to figure out myself, since it could be a thousand things and would be hard for you to see the problem, without seeing the physical product.

But once again, thanks for the help

 

[lordrulz]

hi there,

plz tell me how to interface humidity sensor with pic16f877a. if u could provide a circuit diagram would be great.iam using hih4000 sensor.