I have a lamp in my front hallway that uses a small light bulb, and since I moved in here, it's been an LED type. In the last day or two it became extremely dim, and I had to replace it. I'm wondering what kind of LEDs it uses. They are rods about an inch long, and I wondered whether they might still light up, if there are electronics in the base of the bulb which could have failed. So I broke the bulb and tried clipping the LEDs out, but I can't make them light up on a bench power supply. Could it be that the little rods actually do get the full line voltage, and somehow regulate the current? Maybe someone knows how these things work.

 

In those lamps there is a power supply, often a capaciative dropper also called a transformerless supply. The line voltage is dropped, according to the number of LEDs that will be powered in a series.

Those filaments are composed of many LEDs in a series and may require a considerable voltage to light. It is not uncommon for the LEDs to be receiving 70V, so they might be running on 17.5V or more each. They should start to visibly light in a dark room before this voltage.

Big Clive has quite a few videos on filament lamps, here’s one that should have some helpful information , there are others to check too.

 

The one I investigated is 19 white LED's in series.
From a 230VAC lamp, that's each "filament"

 

They have a limited life because the LEDs have insufficient cooling being in the glass envelope.
About time we moved away from lamps that have to look like 1900's carbon filament light bulbs. Or bulbs made to look like candle flames!

 

They have a limited life because the LEDs have insufficient cooling being in the glass envelope.
About time we moved away from lamps that have to look like 1900's carbon filament light bulbs. Or bulbs made to look like candle flames!

You might want to investigate "Dubai bulbs".

Big Clive has covered them.

 

Those long rods are indeed LED strings and they do require a much higher voltage. And it is quite possible thwt one or more of them have failed. A simple non-isolated variable rectified mains power supply would allow testing them, but such circuits are not allowed in this venue. Beware that any such supply does pose a shock hazard from any part of the circuit, thus caution is mandatory.

 

Hello,

This page has also some info on the led filaments:
http://www.electricstuff.co.uk/ledfilclock.html
They even made a clock with them.

Bertus

 

I love how the GE lamps are marketed as "high definition".

 

The guy in the video has a severe accent. He probably drives a caw. His ocean is full of wotaw.
Wikipedia describes the filament LED clearly.

Big Clive is a very well respected expert on LED lamps and has a special interest in the practicalities of them. He has made many extremely informative videos of LED bulb teardowns including conventional and filament styles.

His Scottish accent is not at all hard to follow and his content is top notch. He's an exceptionally good resource.

That video is also, specifically, about Dubai bulbs, and why and what they are.

 

Yaakov, thanks for the link to Clive's video. I didn't find his accent hard to follow at all! It's interesting that he was curious about what's in those little LED rods too, but if the individual LEDs are connected with so many in series, I don't see much value in keeping them. The voltage needed to drive them is too high to work with most of the components and power supplies I use. I suppose it would be possible to drive them with a boost converter, but I'm not that eager to use them.

If the LED strips do fail through overheating, it could be because they're inside a glass bulb, or it could be that the actual LEDs are inside a silicone sleeve and don't lose heat efficiently. Either way, it doesn't seem like a very good design.

 

https://www.osram.com/os/press/press-releases/osram_adds_filament_leds_to_its_product_portfolio.jsp

https://www.osram.com/ecat/DURIS® L...im_web_catalog_103489/prd_pim_device_2402552/

 

Part of Clive's speech accent is when he starts a sentence loudly then it fades into a mumble or he runs out of breath. Many words are spoken too quickly. Maybe he has only one lung?
My neighbour has filament LED light bubs in his yard and some are obviously burnt out.

I wonder why my city's LED street lights are turned on all day and all night? Each one has a little antenna (for a modem?) on top.

AG, that fading out towards the end of every sentence is a nasty speech flaw afflicting many people. Worse yet, when I have told some of them that their message is important to us and therefore please speak so that we get your important message, usually it makes no difference. It is indeed quite unfortunate that so many are afflicted with such a nasty speech failure.
( If it sounds like I am being hard on these people, that is my intention!!! An accent is no problem, but not speaking up is a problem.)