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Old 12th Oct 2020, 6:43 am   #21
broadgage
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Default Re: Lamp for elderly anglepoise light

Quote:
Originally Posted by trsomian View Post
Thank you all. I bought an LED filament lamp and indeed it balances perfectly. A minor point, but exactly how do these lamps work; from what little I can see it contains no electronics?
Most types contain contain an electronic driver circuit concealed in the base of the lamp. This may be determined in two ways, either break open the cap of a used lamp.
Alternatively connect the lamp to a Variac or similar and observe the input current at different voltages. At 220 volts, the mains input current will be greater than at 250 volts, indicating the presence of a regulating circuit.

A simple capacitive dropper would draw less current at a reduced line voltage, and produce less light.
Also, many types of these lamps are rated for operation from 50 cycle or 60 cycle mains, a simple capacitive dropper would draw significantly more current at the higher frequency.
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Old 12th Oct 2020, 8:23 am   #22
trsomian
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Default Re: Lamp for elderly anglepoise light

Well the only sign of a circuit board is entirely within the bayonet cap, and it has a hole in the middle where the seal of the bulb passes through it, so if there are SM components on it they are only small ones; there are no signs of parts on the side I can see. Also the bulb appears to be at least partially evaluated. Why would an LED require the bulb to be evacuated and/or a special filling gas. All most puzzling.
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Old 12th Oct 2020, 9:47 am   #23
Nickthedentist
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Default Re: Lamp for elderly anglepoise light

Let's have a photo, then.
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Old 12th Oct 2020, 10:33 am   #24
trsomian
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Default Re: Lamp for elderly anglepoise light

I will try to get a photograph, but looking again there is a four pin device, I suspect a SM bridge rectifier visible and a tiny 2 terminal device, probably a resistor
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Old 12th Oct 2020, 11:29 am   #25
trsomian
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Default Re: Lamp for elderly anglepoise light

Photographs
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Old 12th Oct 2020, 2:18 pm   #26
broadgage
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Default Re: Lamp for elderly anglepoise light

I see no merit in the bulb being evacuated, a filling of gas or air would help in transferring heat by convection.
A sealed bulb even containing air would be preferable as the entry of dust, insects and water vapour would be prevented.
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Old 12th Oct 2020, 7:05 pm   #27
Trigon.
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Default Re: Lamp for elderly anglepoise light

An interesting article:-

https://www.ledinside.com/knowledge/...filament_bulbs

Quote:
One of the novel approaches to thermal management is to use a special gas mixture inside the glass lamp to facilitate the heat transfer to the glass surface more efficiently than just relying on convection alone.
Cheers
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Old 14th Oct 2020, 7:38 pm   #28
trsomian
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Default Re: Lamp for elderly anglepoise light

Having found a suitable lamp and being puzzled as to how it works I thought I might see what the current waveform is like. Somewhat horrified at what I found I tried a "normal" LED lamp, and two CFLs. All of them are horrible (hover over the pictures and the file names should tell you which is which).
The electricity supply companies must hate these things
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