Very Simple Light Meter
Very simple light meter can be constructed using LDR (light dependent resistor) wired in series with a battery, variable resistor, and ampere meter. Here is the schematic diagram of the circuit:
The ampere meter is a 100 uA analog meter. Don’t expect too much about the linearity, absolutely can’t be compared to standard light intensity meter which measure luminosity in a standardized way. This simple instrument is useful only for comparative measurement, or just to give a rough estimation of lighting condition in a room (whether it has a sufficient lighting or not).