[Need Help]Read circuit,,

[cacingidop]

Hi,

Can someone please read this circuit about 'automatic watering plant' for me,,

any help appreciated,,

This circuit have been modified by audioguru,,

tqvm

 

[audioguru]

You forgot to ask your question about the circuits.
What do you want to know?

 

[cacingidop]

err,,i just want to know the operation of the circuit u have been modified,,so that i can understand it more,,maybe i can try by myself,,

tq in advance,,

 

[audioguru]

The first Cmos Schmitt-trigger gate is an inverter oscillator so that the probes are fed with AC to avoid plating on them which would happen with a DC signal.
The second and third gates produce a pulse-width-modulation output determined by the resistance (wetness) of the soil.
The 47k resistor and 22uF capacitor smooth the PWM waveform into a variable voltage.
the 4th gate triggers the transistor when the voltage drops to its Schmitt-trigger voltage level.
The transistor drives the relay for the watering pump.

The LM3914 is a voltmeter that shows the filtered variable DC voltage which shows the wetness of the soil.

 

[cacingidop]

Tq soo much,, appreciate it~~