I have a downstairs bathroom that sits close to the middle of the house. It has no windows and it is pitch dark when the door is closed. I had a regular night light, but I wanted something different that does not plug in, so I used two high power LED's and placed them into the switch cover.
These are 8 mm LED's designed to operate at 3 Vdc and 35 mA. They are very bright at 3 volts and light up with as little as 2.4 volts. With 3.8 volts, they are super bright. That seems to be the maximum voltage that they can safely take.
They are clear and blinding to look at, so I made them opaque by sanding them a little. Much better on the eyes that way.
I searched the WEB for a circuit to use but there is too much confusing opinions. I ended up experimenting until I found a suitable circuit. Many people use a single diode as a rectifier but I have many of those small bridge rectifiers so I used that instead. It greatly minimizes the flickering compared to the single diode. This is the circuit that I used.
I started with a 47K ohm ½ watt resistor. It was OK but not bright enough. Then I tried a 20K ½ watt resistor. Very nice but the resistor got a little too warm. Next I tried a pair of 47K resistors in parallel which equals 23.5 K ohms. Nice and bright and the resistors stayed cool because they can dissipate 1 watt in parallel.
OK, time to wire up the thing. I put a fuse in the line for peace of mind. I used a ½ amp pigtail fuse because that was the smallest I had but something as low as 100 mA will work.
The power going into the LED's is 5 Volts (that is 2.5 volts per LED) and only 4.5 mA. They will last a long time with that little current. Power consumption from the 120 Volts is about half a watt.
I did not leave any of the wires exposed. I enclosed all the connections in heat shrink tubing or covered them with hot glue.
Anyone that wants to do this should be familiar with and feel comfortable working with high voltage. This voltage is high enough to hurt or kill. Kill is not a good word to end this so…
PEACE
Ed