To enhance my homemade switch, I used a light-controlled variable resistor (photoresistor) in my circuit so that when the lights in the room are turned on, the LEDs around the mirror light up. When the lights are off, the LEDs turn off.

This would be practical if the lights were perhaps white and very bright, for example, as one might want to have this mirror illuminated on a vanity or bathroom counter.

Here’s a schematic of my original circuit and my enhanced circuit. (No real reason for losing 1 LED besides the fact that I burned out all of my red LEDs and just used 2 yellows for simplicity.) In wiring the actual mirror, I simply replaced the resistor with a photoresistor.

When the lights are on around this circuit, the resistance of the photoresistor is lower, so the LEDs will light up. When the lights are off, they’ll go out.

Next, I used the Arduino as an in-between from the new analog input, and the LED output. I had to change this circuit in order for the Arduino to work. The variable resistor (photoresistor) has to be converted to varying voltage so that the Arduino can read it. I added a resistor to affect the voltage. The video shows me affecting the sensor with my hand by covering the sensor instead of turning on and off the lights.