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PIC + humidity sensor

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stroma

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pic humidity

hi,
i need to interface capacitive humidity sensor /220 pF/ to PIC. which is the best way to do that with minimal component count?
thanks
 

xirix

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humidity sensor ic

Add 1 resistor to obtain a series RC connection.

----pinA
|
|
|R |
| |
|
-----pinB
|
== CAP
|
_|_ GND

Drive pinA to charge the capacitor, watch pinB for rise time.
Better performance if you have a A/D convertor (internal) on pinB.
 

crazyduck

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pic humidity sensor

Hello,
You can use:
An oscillator schematic and calculta the frequency with the timer of the pic.

You can use a controlled constant current generator to supply your probe. You command the generator with a constant time and you'll use a CAN to convert the voltage of the probe. U=(I*t)/C.


CD:)
 

Kripton2035

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humidity sensor earth

you can also use a sensirion sht11 digital sensor, which has a far better accuracy and is in fact not so expensive and easier to interface (all sources codes provided on the sensirion web site)
 

sadat007

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free samples humidity sensors

try to find uc examples that have builtin comparator like 89C2051 and some picks too. on www.atmel.com and www.microchip.com. The comparator user in examples for determining unknown input, value of cap and value of resistor. Examples like find value of pot also......
This may also help
 

crazyduck

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pic interface circuit for humidity sensor

Hello,
If you want to use SHT11 from sensirion you can have a free sample of this part on the sensirion web site.

CD :)
 

stroma

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pic humidity schematic

using SHT11 is too expensive for me. :(
Now I’m trying to measure capacitance using R-C network, described by xirix. Similar method was described in microchip’s AN512.
Alternatively I will try to feed sensor with 1 kHz /from pin of the pic/ and measure voltage drop over it.
 

Kripton2035

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sensors humidity on pic

stroma said:
using SHT11 is too expensive for me. :(

you can get a one FREE sample from their web site...
if you have some friends, you can get as many samples as friends... :D

if it's for industrial use, okay it's expensive.
use rc network...
 

stroma

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sensor humidity pic

Kripton2035 said:
if it's for industrial use, okay it's expensive.
use rc network...
yes it is for industrial use. probably I’ll need about 20 sensors monthly… i don't know for sure.
Sensirion doesn’t send samples for my country :(
The only option is farnell
here are some cheap sensors
https://www.k-won.com/english/products/prod_rhk1an.html
 

Fragrance

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pic humidity circuits

hi,

here is some from me one thing from me other from net hope this will be help full
 

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