This basic project shows how a light dependent resistor (LDR), can connect straight to a voltage level meter, (LM3914)and show the voltage in .35v incrementing steps, when the last led just lights, this is approaching 3.6v, as 1.4v is lost as the power supply to the lm3914 is 5v. (some earlier boards may state 5v scale on the silkscreen).
the light dependent resistor circuit can be altered to suit ambient light conditions, by changing the value of the 10k potentiometer (VR2) until a good swing or range is realised on the voltage level meter, this can be tested by moving your hand over the (LDR). If the light is switched off in the room the effect can be seen as the voltage range should drop quite considerably. This is a voltage divider circuit, however using the (LDR), which is actually a form of resistor, whose resistance is inversely proportional to light falling on it. As light intensity increases, resistance falls. See photos below, when covered with a pen top, no voltage is seen on the LM3914’S Display, when removed a voltage then lights the led display, which represents the ambient light conditions.