The telephone line status indicator to prevent the hearing others talk on the phone accidentally and a Protection to making phone calls simultaneously. [...]
This is a simple metal detector circuit, Can find various metal and adjustable sensitivity Easy to use near metal. use IC-NE556-Monostable multivibrator
This fine 1.5V battery tester circuit using LM324, Can measure the voltage of the 1.5V battery AA or AAA. As decimal point. Easy to use by LEDs display
Why withered trees. It is dying. Oh, the soil is too dry. How can we use electronics to help trees? Build Simple soil moisture alarm circuit. The tree is very…