Wet and Dry Sensor Circuit in one (Basic)

  • #1

Main Question or Discussion Point

Hi, wondering how I could combine a simple wet sensor circuit and a dry sensor circuit into one?

The type of wet sensor I'm looking at is like this:
27yakio.jpg

and the dry sensor is the same except the sensor and variable resistor switch places.

How could I combine the two into one, so that the circuit works when:
1. The wet sensor is wet (touching water).
2. The dry sensor is dry.

-Thank you!
 

Answers and Replies

  • #2
100
1
remove the buzzer lead from the transistor collector and wire directly to 0V
 
  • #3
100
1
i guess the more useful answer, if what you really want is two outputs, is to think of the http://en.wikipedia.org/wiki/Resistor%E2%80%93transistor_logic" [Broken]. might need some biasing resistors on the second stage. logically, it'd be like this:

7TypE.jpg


if that wasn't what you had in mind, then my guess is that you're wanting an analog circuit. yours appears to be digital, with the pot tuning it for a desired conductivity across the strips.
 
Last edited by a moderator:
  • #4
Sorry I don't think I explained this very well.

What I want is to have one circuit which combines these two circuits: (one wet and one dry), so that there is a wet sensor and a dry sensor in the one circuit, and the circuit will work when the wet sensor is wet and the dry sensor is dry.
34i2res.jpg


I'm just not sure how to combine them into one.
 
  • #5
5,439
7
I think the question people are asking is

Do you want either the wet sensor or the dry sensor to operate your trigger

or

Do you want the trigger to only operate when both the wet sensor and the dry sensor give a signal simultaneously?
 
  • #6
100
1
is this homework?

i believe what you're asking for is basically replacing the two transistors with a two-input NAND circuit that drives one buzzer when sensor A is dry and sensor B is wet.
 
  • #7
vk6kro
Science Advisor
4,081
40
[PLAIN]http://dl.dropbox.com/u/4222062/wet-dry.PNG [Broken]

I think this would work.

If either diode d1 or d2 has its cathode pulled low, then the transistor will not get base current so it will stay off. If they are both high (meaning the dry sensor is dry and the wet sensor is wet) then the transistor will turn on and sound the buzzer.
 
Last edited by a moderator:
  • #8
Thanks very much for the replies :) Very helpful.

And yes I want them to work when both the wet sensor and the dry sensor give a signal simultaneously. :)
 

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