Circuit detectors and sensors based electronics projects

This rain detector electronic circuit project is an very simple alarm circuit , that will start an audio warning , if the liquid is present on the sense pad . This rain detector electronic circuit diagram is based on two transistors . When the sense pads conducts , Tr1 and Tr2 from an audio oscillatory circuit  that will generate a pitch sound .

This circuit needs a 12 volts power supply circuit and the speaker needs to have a 32 ohms . The sense pad can be constructed on a small piece of printed circuit board .

This level liquid sensor electronic circuit diagram is based on a common Ca3410 operational amplifier IC . This level liquid sensor electronic circuit use two plates sensors ( two probes ) , one for the high level an one for low level .

If the level of the liquid is not in the adjusted range the LED will glow . The circuit require just a CA3410 operational amplifier and other few common components . This dual liquid level sensor require a 15 volt DC power supply circuit .

This Light Dark switch activated relay circuits schematics are the simplest electronic circuits that can help you to activate other electronic device at the light or dark .
This Light Dark switch activated relay circuits are very simple and require one electronic relay and other few common components that are not critical . For Light Dark switch activated relay circuits you need to use a 5-6 volts electronic relay .

The R2 potentiometer is used to adjust the trigger on level .The diode in the diagram shows to be 1N914. This is ok if you have a light-duty relay, also the 1N914 is a signal diode so actually does not qualify.
If you don’t find the 1N914 you can substitute it with a 1N4001 diode (or better) instead. The 2N2222  (Q1) transistor can be substitute with :NTE123A, ECG123A, PN100, or other similar types . The R1 component is a photo resistor .