For my newest project, the “intelligent desk clock” (I shortly mentioned it at the end of the last post) I need to have big momentary switches that could be illuminated. The idea is to let the switch blink if there is user interaction needed.
I found some switches that need old-style bulbs with “telephone lamp” socket, technically a “T5.5” or “T5.5k” socket. These are usually bulbs running at 12V or higher. I want to realize the project with an Arduino or a Raspberry Pi, so 5V is the voltage I have available. LED lamps with T5.5 socket are rather expensive, luckily I was able to order 10 pieces for 7 EUR from ebay. They do have red LEDs but I thought I could desolder them and solder some white ones to the socket.
Today I found some cool switches at my electronics shop, immediately purchased a bunch and at home, was able to completely disassemble the switch. So I now am able to put some label behind the orange button! Of course the shop had the fitting bulbs in stock, with real lamps rated at 12V, but for 0.5EUR a piece. So I took some, too.
Here are pictures of the switch and the disassembled parts:
Make your own T5.5 LED lamp
Take a look at the T5.5 lamp from the shop. It’s just a metal socket an the bulb soldered to it. The metal parts are glued to the bulb with tiny spots of some hot glue. With the help of a scalpel and some brave cutting and bending (watch your fingers if the glass breaks) the bulb can be detached from the metal socket. With a firm pull the whole bulb can be teared off. Now take a soldering iron and clean the soldering spots and, using the scalpel, clean the glue residue from the socket.
Shorten the wires on the LED (remember which side is Anode and Cathode, respectively) and the resistor (I used 220 Ohms, the usual value when using 5V and an LED). Solder the resistor to one wire on the LED and bend the wires slightly outward so they will make contact with the metal socket when fitted in. (One square of the paper is 5mm x 5mm)
Now fit the LED into the socket so that the socket is just around the bottom of the LED. You will need some sort of fixation tool like alligator clamps to make your life easier. Now cautiously solder the wires to the socket and you’re done. You should end up with something like this:
You will definitely need all your patience making this LED thingy. Taken into account that an LED lamp with T5.5 socket will cost around 5EUR (6 USD) each, it’s worth the effort.