While many projects featured here involve microcontrollers, sometimes this isn’t the best way to do things, perhaps representing a waste of power and/or resources. This automatic battery powered lighting project takes things back to the basics, with only a transistor and LDR for control.
The build seen in the video below starts off with cutting out an appropriate section of perfboard, then shows everything soldered on, using component leads to help connect everything. The circuit diagram can be found at 1:30, including a set resistor and LDR used to trigger a transistor, which in turn lights up a powerful LED. Power is supplied by a 9V battery, attached to the device with a standard connector and hot glue, creating an all-in-one unit.
Notably, you could make this device with different “R1” values to regulate just how dark it needs to be to turn on the “emergency” lighting, and depending on what type of LED you use, you’ll likely want to add a resistor inline with the LED and power supply. However this project is built, it’s an idea that could function as both a very practical project, or a good intro to electronics for those that want to dive in to analog hardware hacking!