I want to put 3 leds as night light to some power outlets around the house. I also want to keep them discrete so the power adapter (110v to 5v) has to be small.
I don't want to use a simple resistor voltage divider (don't not think it is safe). But even smallest transformer is not small enough to put into space around outlet.
How can I get 5v dc from 110v safely with smallest possible way?
Best Answer
There are several ways you can do this.
I'd start off by seeing if any of the cell-phone charger wall-warts are sufficiently small. These normally supply about 5V at current ranging from 100 mA to 2 Amps. The Apple cube adapters are nice and small (about 2.5cm cube).
If that's too large, you can purchase replacement wall receptacles that have a built-in 5V USB power supply. You could assemble the LEDs & current-limit resistors right onto a cut-down USB plug.
You can also do a capacitive-type power supply. However, I'm reluctant to steer you in this direction if you aren't aware of the hazards involved and know how to choose the appropriate components. This is one situation where choosing the correct capacitor and resistors means the difference between a safe circuit and a fire hazard.