I'm trying to make a lamp from my gf's favorite beer. It's a bomber(16oz) bottle that I'm running a DIY lamp kit through. I'd like to add two little red LED lights that are connected to the switch of the lamp so that the lights act as little red eyes on the bottle. Does anyone know if this is feasible? Will it need its own power source or can I run some extra wire from the light switch and power those two lights too? I have zero experience with this and could ultimately do the project without the LED lights but it would be that extra special touch for the holidays. Any help or pointing in the right direction would be greatly appreciated.
The easiest way to run an LED off of 120VAC is to use an LED that's already designed for 120VAC, like a 120VAC LED Panel light. They come in a wide variety of sizes, colors, and form factors.
(Photos from Digikey's catalog).
Just keep in mind that 120VAC is dangerous, and if you're not actually going to panel mount them where only the front of the LED is exposed to the user with the rest of the LED shielded by an insulating or grounded panel, make sure that you keep them safely isolated so the user can't inadvertently come into contact with the back side of the LED housing or wires.
edit: I am assuming your lamp kit is a standard 120VAC powered lamp like most in the US.
It's doable but probably a lot more trouble than you want to go to. You can't just tap the 120VAC power and connect it to a couple inexpensive LEDs. The LEDs run off a lower voltage. You could use a DC power supply, say 12VDC or 5VDC, to power the LEDs. You could run a separate cord from a pluggable DC power supply, aka a "wall wart," to the LEDs. (Putting a DC power supply inside the bottle isn't going to work...) You'll need a current limiting resistor wired in series with the LED.
The main thing to remember, the 120VAC is dangerous, don't get creative with it, low volt DC is pretty safe, but nothing is perfectly safe.
I use a very simple circuit, shown here. It would be wired in parallel with the lamp bulb, after the switch.
For me, this circuit gives me two red indicator lights to signal that the inverter is turned on.
The .47 uF cap is high voltage, and the resister is 1/2 Watt. The resistor can easily be a mini 5K or 10K pot for brightness adjustment.
WARNING: The 120 VAC portion of the circuit can hurt you. Please do not attempt to do this unless you can exercise appropriate caution.
I replaced the 1N914 with second LED, so I use one at the source of power then use the second one closer to my workstation. It would be easy to mount the two together so they look like two little red eyes.
The LEDs I use are prepackaged with threaded mounts. They look a lot like those designed for 120V, ready for panel mounting. They were like a dollar a dozen on the slow boat via eBay. But you can use any red LEDs you'd like. Normal LEDs tend to be a couple or three mm in size, but I'll bet you can find 10mm red LEDs with a little searching.
Here is the schematic:
--EDIT: I found two sources for larger red LEDs.
Both listings have bezels and are current-limited.
USA would deliver in days, and HK in weeks.