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I can honestly say that this is my first endeavor into the realms that is circuitry. I want to build a device that runs on 9volt battery and can indicate (via LED or sound, [preferrably LED]) moisture. Can anyone point me in the direction as to what materials I might need? Please be specific as I'm brand new to this...THANKS SO MUCH! -Ryan

Hi.
The humidity sensor can be obtained canibalizing a defunct video tape recorder.
Connecting the 9V battery and an adjustable resistor and an analog galvanometer in series, you can get a reading that would have to be calibrated to a dial.
To use a led, it would need a comparator chip circuitry set to the humidity treshold you want it to come on/off.
If you say you are very new to this, could be better to do it with the analog meter to start, it would take only the three components.
To be specific as you ask, would mean knowing which sensor and which meter characteristics will you use in order to calculate the resistor value.
Just play with them to learn.<p>Good luck,
Miguel

Hi.
The humidity sensor can be obtained canibalizing a defunct video tape recorder.
Connecting the 9V battery and an adjustable resistor and an analog galvanometer in series, you can get a reading that would have to be calibrated to a dial.
To use a led, it would need a comparator chip circuitry set to the humidity treshold you want it to come on/off.
If you say you are very new to this, could be better to do it with the analog meter to start, it would take only the three components.
To be specific as you ask, would mean knowing which sensor and which meter characteristics will you use in order to calculate the resistor value.
Just play with them to learn.<p>Good luck,
Miguel

You can also purchase dew or moisture sensors.<p>Going to try a moisture sensor in my ongoing saga of rain detection.<p>bodgy

The 555 chip is good for humidity and moisture sensing. Most 555 inputs circuita are sensitive enough to go off when touched, or when placed parallel to the ground, will go off with moisture present. The spacing distance and length of the probes between the ground and #3 pin [trigger] is adjustable both in distance and sensitivity by making a maze like pattern which the two leads . You also learn about making your own circuits, assembly, and test/trouble shooting, and all for a dime or so. You can also make the chip a oscillator on the out put to drive a speaker, or a led, and "alarm" you as to when its going off. When moisture is present noise or light alerts to to its presence.