Playing with LED Filaments.

CAUTION!  ELECTROCUTION HAZARD.  Its just a bunch of 9 volt batteries, but guess what, if you put enough of them together you can stop your heart.

Something is happening to our light bulbs.  Like the movies where alien pods secretly replace people, LED Filaments are secretly replacing our LED light bulbs with bulbs that harken back to a bygone era of Mazda lamps.

( Not my photo, but the rest are.  I forgot to take a shot of the bulb intact. )

The filaments are really a thin glass rod with LED's formed on their surface created using a SoG process, silicon on glass.  Then a bead of silicone rubber impregnated with phosphor is applied.

So first you have to break some eggs.   I placed the bulb in a ziploc bag and removed ( scored and smashed ) the glass envelope.  This allowed me to fire up the bulb with a dimmer to measure the voltage across the elements to ascertain the range of voltages they expect.   FOR THIS BULB the elements started to produce light at about 65 volts, and caught fire around 75 volts.

The elements are easily removed with a diagonal cutter.

LED's are non linear devices that are designed to operate at a specific current, not voltage.  These are related, but the reason LED bulbs have fancy power supplies is because they need them.  You need to limit the current through the LED to keep it from burning up.  So the fancy electronic modules in the base of the bulb handles this it will limit the current to the proper value.

The voltage across the elements was direct current, so naturally I thought of a series of 6 or 9 volt batteries.

DANGER!  72 volts is enough to kill you if you really work at it.  Respect it!

These are crappy dollar store batteries.  The non-load voltage was about 75 volts.

First light.  This is ~1 watt LED at full brightness

With a single element, the battery array could over drive the element, and eventually incinerated it.  Getting it down to 7 x 9volts the element would produce some little bit of light and was under driven.

63 volts: low output, under driven.

Reconstructing the elements into useful shapes is easy - and of course with enough of them you can create any pattern you need to deliver as much light as you want in a very small space.

I used beefy wiring, but that is entirely unnecessary.  More flexability would have been better.

With the additional drain of 6 elements, the 9 volt batteries themselves act as the current limiting device - they can only supply so much current.  With all 6, they ran at full brightness and did not self immolate.

LED-Henge

Obviously the color temperature is all wrong for most applications, but these elements will be available in a variety of color temperatures and CRI's eventually and will certainly be usable for a variety of applications.

The advantage to LED filaments is the lack of the need for a huge heat sink, so smaller bulbs that look and feel like lightbulbs.

I am envisioning a flat array of elements that could replace ring flashes / opie lights.

LED's also lend themselves to be over driven for short periods - creating arbitrary shaped LED flash units or special lighting.  The fundamental difference between this and traditional LED is that they are not point sources, and thermal management seems somewhat easier.

So as a proof of concept - it looks good.

Interesting! Have a product link for these?

It's interesting that each filament seems to want around 65 volts before they even start illuminating - that indicates that they consist of a LOT of LEDs in series internally. Based on how you describe this, it sounds like in the assembled bulb the filaments are wired in parallel and not series?

With a 65+ volt Vf, I wouldn't be surprised if these particular bulbs skip the usual driver and just use a current limiting resistor...