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. [...]
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
Simple light meter circuit idea using normal diode as sensor, amount of light by voltmeter. Using op-amp-CA3140 and a few parts.