LM358 Photodiode Light Meter

Turn light into a millivolt reading using a BPW34 photodiode and an LM358 transimpedance amplifier.

Difficulty: Breadboard. Estimated build time: about 45 minutes. Estimated parts cost: about US$3.50. 9-part bill of materials with live supplier pricing. A simple light meter that converts the tiny photocurrent from a silicon photodiode (a few microamps in room light, hundreds of microamps in direct sun) into a clean output voltage you can read on any multimeter or feed into an MCU's ADC.