Interesting new(ish) light source.

[adam2]

Most of us are probably familiar with LED "filament" lamps, glass bulbs that contain or more long strips of tiny LEDs that somewhat resemble an incandescent filament. A wide variety are available including mains voltage, other voltages, in various colours. The driver circuitry is in the cap of the lamp.

 

A relatively new product, is the bare LED strips, not mounted in a bulb, and without any driver circuitry. This sort of thing,

ebay link

 

 

No specific recommendation is made regarding that particular product or that particular seller, link provided to illustrate the TYPE of product to which I refer.

 

Very little technical information is provided, and a little experiment may be called for. Some types are listed as being "3 volts" which I would presume to mean that they need connection to either a constant current driver circuit, or to a higher DC voltage via a dropper resistance.

Other listings don't even give the voltage.

 

Please be very careful in experimenting. The voltages involved are almost certainly harmless but enough wattage and enough current to start a fire are required. The longer lengths may require several amps, enough to start a fire if a fault occurs.

 

Might be useful for special effects ? Battery operation would be possible.

 

ISTR that BigClive did a technical review on youtube of this or a similar product a couple of years ago.

Might be worth a look ? Though be aware that the specification may have changed since then. Longer lengths and a choice of colours are now available.

Edited May 25, 2021 by adam2

[alistermorton]

I thought the 3V refers to the forward drop per diode, so if you have a string of 20 LEDs you need to apply 60V, 40 LEDs 120V etc. Clive will be able to give chapter and verse, I guess. OTOH, while some filaments quite clearly have a lot of individual LEDs, others appear to be one huge diode, so I guess it varies.

 

Added: The packs of COB filaments say they're 2.9-3.1 V 0.15W which is only ~50mA - that's actually perfectly manageable, and they may well respond well to PWM dimming. Worth a play, I think..

Edited May 25, 2021 by alistermorton

[DrV]

I also thought that these strings were lots of LEDs in series rather than parallel. I might get some to play with.

[alistermorton]

Even the extra bright ones seem to be only 3W - 1A at 3V should be manageable. Edited May 25, 2021 by alistermorton

[adam2]

I suspect that MOST LED filaments contain series connected LEDs, but not perhaps all types.

For a mains voltage LED lamp, a driver circuit that gives 20ma at 150 volts is probably cheaper and simpler than one for 1 amp at 3 volts.

 

For lamps with a 12 volt input, then a driver circuit for 3 volts might be cheaper than a voltage boosting circuit with a 150 volt output.

 

I have some 3 volt, 3 watt, E27 LED filament lamps that I suspect contain no control circuitry whatsoever, they work fine directly from a couple of D cells, or three in series with a dropper resistance from 12 volts DC.

[Tom Baldwin]

There's a video by Mike's Electric Stuff on YouTube about them

. Looks like an interesting product!

[adam2]

An interesting link in the previous post, but please be aware that the product reviewed in that link is almost certainly different to the products offered at present on fleabay and elsewhere.