I wanted a blue LED light bulb for our water dispenser. So I decided to make one.

You need...

3 blue or white LEDs
1 100K 1/2W resistor
1 1N4004 Diode
1 dead (or not) C7 socket light bulb
3 inch of 1/2 " shrink tube

some hot glue
Soldering Iron
Pliers
Paper tube (paper towel or toilet paper tube)
vice

Step 1: The Circuit

The circuit is composed of a 1N4004 diode, a 100K 1/2W resistor and 3 blue LEDs

Step 2: Brake a C7 Bulb But Don't Brake It!

I used a standard C7 type bulb because this is what fits inside the water dispenser.

This will be our base to attach the circuit

You need to brake the bulb, but, you must NOT brake the inside. To do this I inserted the bulb inside a used paper towel tube. and then squeezed the bulb using a vise. When the bulb is broken, it is possible to remove and brake away the rest of the glass, leaving the inside untouched.

Once you have the inside you can remove the tungsten filament, keeping the two leads.

Step 3: Preparing the LEDs

In order to make the 3 LED in a perfect circle, I used a pen and taped them up together in a circle.
Make sure you have the long and short leads all in the same direction.

Solder the first long lead to the next short lead, and so on. Leaving you at the end with one long and one short lead not soldered. These two leads will be the negative and positive of the LEDs series.

Step 4: 3 Blue LED in Series

This is the LED element

Step 5: Solder the Resistor and the Diode to the Two Bulb Wires

Solder the resistor and the Diode to the two bulb wires.

One wire has the 100K 1/2W resistor.
The other wire has the 1N4001 diode.

Take note of the diode polarity, the output of the diode will have to go to the short lead of the LED module made before.

The resistor will go on the long lead of the LED module.

Step 6: Tape the Components

Tape the components to keep them in place and to isolate the 120V from each other and the rest of the components.

Step 7: Install the LED Module

install the LED module.

Slide it on and solder the diode and the resistor to the long and short leads.

The Diode + should be on the short lead of the LED.
The resistor should be on the long lead of the LED.

Step 8: Add the Head Shrink and Glue

Add the heat shrink tube over the circuit,

leave a bit other the metal socket and shrink it a bit so it make a seal. DO not shrink the hole tube.
Only over the socket.

Fill the tube with hot glue. let it cool down in a refrigerator for 15 minutes. This will make sure the glue is cold. This will give you a chance to heat the shrink tube at the and without melting the glue too much.

Step 9: This Is It

Final product. You can bend the LED to the side a bit then add more hot glue to isolate

Screw this in the socket and there you have it a C7 120V blue LED light.

And yes you can add more LED in series and parallel
You will have to recalculate the resistor

You might think this is a long process for nothing. You are right! you can actually buy C7 120V LED bulb already made... But mine was made with stuff I already had around and it was fun to make...

Step 10: View From the Inside the Dispenser

This is the installation. The new LED bulb fits right in where the old lamp was.

Step 11: Second Shop Without the Flash

you can see the LED is directed to the tab you push to get the water... It's a discrete light that will not light up half the kitchen like the old one...