These are four light sensor alarm circuits, when be become dark, or Light sensitive switch.Use part is important light sensor LDR light dependent resistor [...]
Include: Volt meters :: Sound level meter :: Analog vu meter :: Soil moisture meter :: Digital meter circuit diagram :: Temperature measurements :: Electronic measurement tools :: Frequency meters :: Best battery tester :: Transistor tester project
Here is simple ICL7017 digital voltmeter circuit easy to build and cheap because it is high technology, by single IC,small number, along by LED 3 digit.
This Diode tester circuit can check the diode the good or bad and also can indicate its polarity. using op-amp 741IC and LED for display. [...]
This is Simple non-contact voltage tester using transistors next one circuit that use all transistor as main,it is cheap and easily build. Which many friends likeNon contact AC Detector Voltage. It use CD4060 as main