Illuminated AC rocker switches - Page 1
Forum section: electronics / projects

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 23, 2025, 11:37:21 pm
content: The old ones with a neon bulb in them. Mine has a flickering failing bulb.So I took it apart to try and see if I can replace just the bulb. I was surprised to see the bulb's leads clip into what I thought was directly the line AC voltage.So I measured the resistance from top to bottom of the plastic piece and it measures about 47K for each pin.I guess each of those little metallic pellets is a resistor, which also resists the mechanical stress of the springs when the switch is together.What are they made of?I don'tneedto know to just plop in a new fresh bulb (when I find them), but Iwantto know...

author: TimFox
author_rank: Super Contributor
timestamp: March 24, 2025, 12:01:43 am
content: The resistance of two resistors in series with a neon bulb would be infinite (at low ohmmeter voltage).Is the white glass object really incandescent?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 24, 2025, 12:28:40 am
content: This is the circuitL ----^^^^-----( )------^^^^----NL= lineN=neutral^^^^ = pellet of 46K--()-- = neon bulb  = probe pointsThe resistor is the two pellets. What are they?

author: themadhippy
author_rank: Super Contributor
timestamp: March 24, 2025, 12:33:19 am
content: possible some form of carbon

author: BradC
author_rank: Super Contributor
timestamp: March 24, 2025, 01:00:35 am
content: Quote from: Alex Eisenhut on March 24, 2025, 12:28:40 amHave you popped them out for a look? My "phase pencil" has a similar looking device. When you look at it side on it's clear it's a chunk of carbon with a couple of moulded/cast end caps pressed on (as themadhippy says).

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 24, 2025, 01:01:46 am
content: Ah you're right, if it acts like a resistor... it is resistor!I was just a bit baffled by the thing, just seeing the end caps. But it's super simple. It's like a big sturdy MELF.I like it.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 24, 2025, 02:46:36 am
content: That's almost certainly just a standard through hole resistor minus the leads and outer coating. 94k is a good value for 120V.You might want to try 2x LEDs in reverse parallel, the green and blue ones are especially bright at low current. One of my favorites is a blue LED or two in series with 2x 470k on a 400V DC bus cap, the glow remains visible until the voltage drops surprisingly low.For more brightness, use more LEDs in series. A tiny PCB of SMD LEDs would maximize the brightness possible in that size although actually making it can be a bit of a (fun!) challenge. Use some regular diodes as a rectifier so you can effectively double the number of series LEDs on each half cycle.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: April 04, 2025, 08:41:37 pm
content: I ordered some green neon bulbs from aliexpress and shoved one in.The other switch still has an old bulb, you can see the barely lit little green line which is all the old bulb can manage. The plastic has a crack so I'm less eager to pop that one open.It's the little things like that I find satisfying. Guess it needs a bit of Windex too.