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why is the US not Metric
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mariush:

--- Quote from: james_s on October 26, 2019, 04:56:16 pm ---
What do you think 12V would solve for lighting? Are LEDs going to magically run cooler if the driver is fed by 12V instead of 120V? My house is almost entirely LED since I changed it out in 2011-2013 and I think I have had 3 bulbs fail in that time, all of which were in enclosed fixtures, I have since found some bulbs that don't seem to mind that. Nobody in their right mind with any understanding of EE would contemplate wiring a house for 12V. Try living in an RV or boat for a while and you'll quickly realize what a hassle it is to be stuck with such a low voltage. A 2V sag under load is no problem for 120V but it's completely unacceptable for 12V.


--- End quote ---
Not 12v but 24v or 48v.
Much simpler circuit inside the bulb: you won't have bridge rectifier, no bulky fuse, no common mode chokes for filtering, no primary high voltage capacitor, no need for transformers with double insulated wires or with space between primary and secondary, no cutouts in pcb under transformer ... a simpler and cheaper inductor instead of bigger transformers...
Better factor correction, you can have a 120-230v -> 24/48v that's 90%+ efficient, with 95+ factor correction instead of separate ac-dc converters in each bulb with 70-90 pfc.

Most led bulbs use small leds, let's say up to 100mA ... so 24v or 48v would be fine for having multiple leds in series, even if using cheapest linear led driver, losses would be very small. ex have 7 x 3v 0.1A in series, then 2-3 of these in parallel  for 21v 0.3a ... you get 7.2w in, 6.3w out .. 88% efficiency with cheapest linear led driver out there.

Cheaper bulbs, or maybe better heatsinked leds for longer life, as the led driver inside may be more efficient and generate less heat. 
much easier to produce 3.3v or 5v for an integrated IC that could do dimming based on signals on the DC input line or from bluetooth / wireless signal.

Less waste that won't be recycled properly...
Simon:
why don't you just have a seperate thread on this?
Monkeh:

--- Quote from: mariush on October 26, 2019, 06:00:45 pm ---
--- Quote from: james_s on October 26, 2019, 04:56:16 pm ---
What do you think 12V would solve for lighting? Are LEDs going to magically run cooler if the driver is fed by 12V instead of 120V? My house is almost entirely LED since I changed it out in 2011-2013 and I think I have had 3 bulbs fail in that time, all of which were in enclosed fixtures, I have since found some bulbs that don't seem to mind that. Nobody in their right mind with any understanding of EE would contemplate wiring a house for 12V. Try living in an RV or boat for a while and you'll quickly realize what a hassle it is to be stuck with such a low voltage. A 2V sag under load is no problem for 120V but it's completely unacceptable for 12V.


--- End quote ---
Not 12v but 24v or 48v.
Much simpler circuit inside the bulb: you won't have bridge rectifier, no bulky fuse, no common mode chokes for filtering, no primary high voltage capacitor, no need for transformers with double insulated wires or with space between primary and secondary, no cutouts in pcb under transformer ... a simpler and cheaper inductor instead of bigger transformers...
Better factor correction, you can have a 120-230v -> 24/48v that's 90%+ efficient, with 95+ factor correction instead of separate ac-dc converters in each bulb with 70-90 pfc.

Most led bulbs use small leds, let's say up to 100mA ... so 24v or 48v would be fine for having multiple leds in series, even if using cheapest linear led driver, losses would be very small. ex have 7 x 3v 0.1A in series, then 2-3 of these in parallel  for 21v 0.3a ... you get 7.2w in, 6.3w out .. 88% efficiency with cheapest linear led driver out there.

Cheaper bulbs, or maybe better heatsinked leds for longer life, as the led driver inside may be more efficient and generate less heat. 
much easier to produce 3.3v or 5v for an integrated IC that could do dimming based on signals on the DC input line or from bluetooth / wireless signal.

Less waste that won't be recycled properly...

--- End quote ---

Where's the significant advantage over existing 12V PoL systems? There's little to gain by upping the voltage over a 2-3m run.
james_s:

--- Quote from: mariush on October 26, 2019, 06:00:45 pm ---Not 12v but 24v or 48v.
Much simpler circuit inside the bulb: you won't have bridge rectifier, no bulky fuse, no common mode chokes for filtering, no primary high voltage capacitor, no need for transformers with double insulated wires or with space between primary and secondary, no cutouts in pcb under transformer ... a simpler and cheaper inductor instead of bigger transformers...
Better factor correction, you can have a 120-230v -> 24/48v that's 90%+ efficient, with 95+ factor correction instead of separate ac-dc converters in each bulb with 70-90 pfc.

Most led bulbs use small leds, let's say up to 100mA ... so 24v or 48v would be fine for having multiple leds in series, even if using cheapest linear led driver, losses would be very small. ex have 7 x 3v 0.1A in series, then 2-3 of these in parallel  for 21v 0.3a ... you get 7.2w in, 6.3w out .. 88% efficiency with cheapest linear led driver out there.

Cheaper bulbs, or maybe better heatsinked leds for longer life, as the led driver inside may be more efficient and generate less heat. 
much easier to produce 3.3v or 5v for an integrated IC that could do dimming based on signals on the DC input line or from bluetooth / wireless signal.

Less waste that won't be recycled properly...

--- End quote ---

Not really. Have you looked at the drivers used in modern line voltage LED lamps? They are not much more complex than lower voltage DC drivers. They are low cost and very efficient, many are now using a single IC. Bluetooth is a train wreck, you are seriously suggesting a low voltage DC lamp that requires built in bluetooth and a separate voltage converter is simpler and cheaper than the $3 LED bulbs we already have that work perfectly well from existing line voltage? And this is going to be worth replacing the existing domestic wiring with something completely new that is far more expensive to install due to much more copper being required for a given amount of power and still won't work for all the large loads? What are you smoking and where can I get some of it? And what does any of this have to do with the metric system?
tooki:

--- Quote from: MagicSmoker on October 25, 2019, 12:34:07 pm ---Sigh... Until American children are taught metric the Imperial system will persist, simple as that. It's not about what is better, it is about what is familiar, and in the US the Imperial system is by far the most familiar one.

--- End quote ---
As an American who went to school in USA: I was taught the metric and imperial systems in elementary school. And that was in the 80s, long after the US abandoned metrication.


--- Quote from: Simon on October 25, 2019, 02:48:13 pm ---yes but we don't have mixed measurements in the same industry like the US space industry did ;)

--- End quote ---
How would one transition an industry from one system of units to another, if not to start converting? It’s impossible to shift everything instantaneously, so there will necessarily be a period when some things are still in the old system and others are in the new one. It’s a no-win situation: if USA retains the old system, the haters accuse of us being backwards and lazy and arrogant (neither is true), but if USA does switch to metric, then the haters accuse of us being reckless for switching. 🙄
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