How to make a rain alarm
Step 1: Grind the oxide layer of copper clad laminate with sandpaper, and draw lines on the raindrop sensor board with marker pen
The lines I painted is ugly
Step 2: Corroding the board in etchant
Pls take a look, the water was still transparent at the beginning.
Corrosion is now halfway. The water seems like a little blue (about 45 minutes later).
Obviously we can not see the copper now.
The water looks pretty.
Step 3: Rub off the black line with sandpaper after drying (you can use alcohol, I don't have alcohol...)
Step 4: Drilling (using a homemade small drill, 1.0 bit)
Step 5: Solder the lead wire to the raindrop sensor board
Step 6: Solder the buzzer module, here is the active buzzer
Here is the circuit diagram
Finally, connect the raindrop sensor board and the buzzer board together.