8 ms·

This is the frustrating thing about LEDs that IDK we can change. If there was a "DC" light socket in the house we could have LEDs outlasting owners, and for ch

This is the frustrating thing about LEDs that IDK we can change. If there was a "DC" light socket in the house we could have LEDs outlasting owners, and for cheap. Nearly all the expense of LED bulbs is the power supply. Everything else is dirt cheap. A single home DC power supply with ~200W of output could light an entire house, flicker free. What's even more frustrating is I think we could fix it. A national regulation for DC light sockets would fix it. Mandate a voltage, shape, and max amperage and BAM, you'll get 1000 different manufactures making standard compliant bulbs and home power supplies that will last an eternity.

petra 4y ago
Would this system need new electrical wiring ?
- wlesieutre 4y ago
  Yes. For the commercial DC lighting installations I've seen they were using power over ethernet. That's not necessarily the only way to deliver DC power but whatever you do it's going to be wired differently from 120 VAC.
  - samtho 4y ago
    I used to do electrical installs in commercial buildings and this was starting to catch on, mainly because the the practice of running ethernet (including the 8P8C aka RJ45 connector, patch paneling, etc) is already established. This always felt very roundabout and requires expensive networking equipment just to run lights which I do not personally like because it will just cause confusion.
    - xxpor 4y ago
      You also get (the wiring for) remote control for free though, which is nice. It seems like there would be a market for cheap as possible 10 mbit switches with 802.3bt/802.3af support though. https://www.amazon.com/Gigabit-802-3af-100Mbps-250Meter-Unmanaged/dp/B0899MWYKL https://www.amazon.com/Gigabit-802-3af-100Mbps-250Meter-Unma... is pretty cheap as is, I'm sure you could buy something in bulk for cheaper.
JohnFen 4y ago
Low voltage DC lighting is a thing that has existed for a very, very long time. That most houses don't have it is more cultural than anything else, in my opinion. That means it's totally fixable. You can install such a system in existing buildings right now, and it's not crazy expensive unless you want to run the wires inside the walls. If we could shift cultural expectations around this, adding a LV system in new construction would not significantly increase the construction costs. It will start to be done if buyers start demanding it.
- yencabulator 4y ago
  For example: the stairwell shin-height lights in this 90s house are 12 VDC. There's a transformer plugged into a wall outlet in the nearby storage closet.
  - midoridensha 4y ago
    That works OK because the transformer is relatively close to the lights. If it were a reasonably-large house, and the transformer were on the opposite side of the house, you'd have a problem with a noticeable voltage drop. All these ideas people are throwing out here involve a single whole-house power supply. If it were for 48VDC, it would probably be fine, but 12V would result in significant line losses.
    - yencabulator 4y ago
      We already see transformers for a run of e.g. track lights, low voltage lights on tension wires, and so on. That's been a thing ever since halogens came to market. Having multiple transformers is perfectly doable and commercially viable -- though I would appreciate more product availability for something easy to stash in the hollow space of a ceiling, like recessed lighting is installed.
      - midoridensha 4y ago
        I still don't see the point of all this. If you have a handful of lights in a room, and drive them with a single power supply, you're still going to have big problems: the line lengths to each fixture will be different, resulting in different voltages. You can't drive LEDs that way with good results: they need fixed current. And you can't daisy-chain them either: if one emitter dies, then the remaining ones will suddenly have different current, and probably die quickly. The proper way to drive LEDs is with a power supply very close to the emitters and designed specifically for those emitters and the (short) wire length to them, not 4 meters away and not with some variable-length wire that can't be designed for. Everyone here is complaining about ultra-cheap LEDs that don't last very long because they're poorly engineered, but that's exactly what you're all trying to do here by using a separate, shared power supply. You could get away with that in the 1980s using incandescent bulbs, but you can't do it now unless you want the same crappy lifespan and reliability you're all complaining about. The solution is very simple: buy fixtures that are engineered well. Switch-mode power supply electronics are not expensive at all, but when mfgs cheap out or do a crappy job designing them, you get bad results, usually short lifetime of either the power supply or the LED. What you're trying to do here is buy a really expensive power supply, which has to be engineered to a far greater degree and for a far wider range of operating conditions (since they don't know what you're going to connect to it), just because you had a bad experience buying some $2 light bulb that had a crappy power supply built-in. This really makes no sense.
bryanlarsen 4y ago
We've had 2 standard DC outlets for a while now: 12V cigarette lighter and 5V USB. You do often see them in odd places. But the voltage and wattage of those specs is too low to be useful, so they haven't evolved into DC power distribution. USB-C PD is at a useful voltage & wattage level, and so is Ethernet POE. I wouldn't be surprised to see them start to be used for general power distribution in niche applications, like RV's and off-grid cabins. I don't think we're going to ever get a bulb standard, though.
- zaroth 4y ago
  Cars are starting to move to 48V DC. My under cabinet lighting in the kitchen are powered by DC from a power supply in the basement. I could definitely see this becoming more common. Powering the ~100 watts of fixed lighting spread across my whole house on ten different 15A 120v circuits, each with their own arcfault breaker and 12 gauge copper electrical lines running back to the panel is fabulously expensive for what could be done with a bunch of CAT5 in each floor running to some conveniently located “POE injector” type devices. You would want to be able to take a standard fixture and just push DC through it and use special bulbs with a standard A19 base, but that’s problematic when the next owner tries to screw in a standard bulb - what happens when it sees 48V DC? I would guess if for safety reasons it has to be a non-A19 connector, then your light fixture choices get cut down to almost nothing and no one will make the switch? It’s really interesting to think about, most everything I’m plugging into AC outlets in my house, the first step is converting it to DC. A lot of my outlets I’ve switched to include USB ports so I don’t need the wall warts. If you have solar and battery backup even more-so you start to question why we are wasting so much money moving everything back and forth between DC/AC/DC within a house.
  - garaetjjte 4y ago
    >screw in a standard bulb - what happens when it sees 48V DC? Either it lights up or not? I don't see a problem here. But I'm not sure moving part of power supply elsewhere will help that much, it needs current driver electronics anyway.
  - pwg 4y ago
coryrc 4y ago
LEDs must be powered by a constant-current supply, and distribution does not work well at constant-current, and is always constant voltage. So no matter what you will need some sort of switching power supply. LEDs are like 15% efficient and power supplies are >95%. They just need to be separated slightly so the LEDs aren't heating the power supply. Most recessed LED lighting now has a separate junction box with the power supply.
- samtho 4y ago
  > LEDs must be powered by a constant-current supply, and distribution does not work well at constant-current, and is always constant voltage. So no matter what you will need some sort of switching power supply. I think the biggest problem is that many cheap power supplies cycle at lower frequencies that cause flickering which is perceptible subconsciously. A modern switchmode power supply might operate in the 50-500khz range which will not cause perceivable flickers.
  - int0x2e 4y ago
    The really cheap stuff actually doesn't even have a power supply! There's a breed of LEDs that takes straight AC and rectifies it using the LEDs themselves. By using a large number of tiny LEDs in series (typically in COB form), you can easily reach close to 110v or even 220v, and then you add a small current limiting controller in series that's dirt cheap compared to magnetics... These are super cheap, and appear bright, but they flicker at 120hz, which can be annoying when there's motion or if you're sensitive to it. I'd say it's a very bad choice for a bedroom or living room light, but I have nothing against it for the outdoor lights, signage and a bunch of other applications where cost is king.
    - amluto 4y ago
      I have a serious problem with it for outdoor lighting and signage: it gives me a headache. Enough exposure will make me feel actively sick. The effect is not subtle. Just don’t use these devices, please.
    - 4y ago
samtho 4y ago
I am designing an off-grid cabin with a solar panel array charging a bank of batteries with a propane generator backup. I run ethernet as power with a custom designed PCB that terminates at the outlet side where it exposes a 20 watt USB charging port and an ethernet port. The lights are all basically cut 12v light strips inside of old light fixtures with a custom controller that also terminates PoE. The 48 volts that most PoE standards specify is more than enough to push power down the line for < 100 meter runs. The advantage of PoE here is that anything under 50 volts is considered low voltage and does not need to follow the same rules as normal house wiring. I did not like that everything is hinging upon a beefy PoE switch so I actually made it passive PoE instead by design.
- int0x2e 4y ago
  If you're willing to share your design, I'm sure there are other folks like myself who think this is a cool idea. I've wanted to do PoE (or passive PoE) for lights for a while now...
  - samtho 4y ago
    I am going to open source it. The goal was to be able to get all the SMD stuff available at JLPCB so you can just send it to be fabbed (with some thru-hole components you would just solder yourself) or I would also sell them at cost + 10%. My brother designed some 802.3at chips and was going to have him review my work first as I don't want to send out into the world a poorly design power system (there are enough of those things out there unfortunately).
    - zulfazli 4y ago
      Cant see any github link in your profile. Any way I can get notified when you open source this? Thank you.
    - notjtrig 4y ago
      I'm interested in installing your design in my cabin as well, could also be very useful for boats too.
amluto 4y ago
I think this falls apart in the details. LEDs want constant current power supplies, and their owners frequently want them to dim. So you will still need a power supply. You can fudge it with resisters like in an LED strip, but you lose efficiency and dimming quality. That being said, I expect that power supplies with 48VDC input or so would be cheaper.
- BizarroLand 4y ago
  Maybe this could be a prosumer retrofit thing, where the AC voltage gets converted to DC in the junction box, and then DC is sent down to the fixture. Probably with some sort of current sensing system to make it compatible with dimmers. Pair that with DC A19 LED bulbs that have no internal power systems. Probably expensive to put together and to install, but if the goal was to have LEDs that last longer, that would do it.
  - HideousKojima 4y ago
    >Maybe this could be a prosumer retrofit thing, where the AC voltage gets converted to DC in the junction box, and then DC is sent down to the fixture. The problem is that in 99.99% of homes outlets are on the same circuits as light fixtures, you would need to do some major rewiring.
    - BizarroLand 4y ago
      No, I'm saying you put a module into the junction box that the light fixture is attached to that serves as an AC/DC adapter, current limiting driver, and possibly a dimming sensor that would then provide downstream DC voltage to retrofit A19 bulbs. Those bulbs would then have no internal switching systems to burn out and rely entirely on the module hidden behind the wall to handle their power needs.
  - xxs 4y ago
    You will see need to current drive the LEDs, DC alone won't help.
Zak 4y ago
Trying to cram all the infrastructure for an LED lamp into the shape of a light bulb is a bad idea, even if the input power is DC. Good designs for LED lighting have larger surface areas for heat dissipation and some physical/thermal separation between the LEDs and the power supply. A quality power supply does not produce flicker. As other comments have noted, dimming, or even predictable output requires some sort of power regulation even with DC input. I think the way to change it is to replace sockets with hardwired LED fixtures. This is easy for something like a standalone ceiling light. It may be harder for other devices like ceiling fans that integrate a light bulb socket, but converting those devices to take DC power as in your proposal isn't easy either (most would just get discarded and replaced). Doing it well is more expensive in the short-term than screw-in bulbs. A quick look on Amazon suggests integrated ceiling lights are about 10x the price of LED bulbs, though I suspect the longer service life pays for itself.
- Joker_vD 4y ago
  > Trying to cram all the infrastructure for an LED lamp into the shape of a light bulb is a bad idea, even if the input power is DC. Absolutely, the incandescent light bulbs have that shape for a reason: the screw is small because there is nothing to put in it and it doesn't heat, the bulb is large to dissipate all the light and heat it generates. And the LED light bulbs have exactly opposite problems: almost all of the heat is generated near the screw while the bulb itself generates almost none and the light-emitter doesn't even need the bulb that large around of it. Oh, and the casing around the screw is plastic so the thermal conductivity is horrible. Honestly, it's a profoundly terrible form-factor which we're now stuck with.
  - Zak 4y ago
    I don't think we're exactly stuck with the old form factor. We can start phasing them out. Replacement of screw sockets with modern fixtures is well within the capabilities of the average DIYer (though perhaps some places it's illegal for anyone but a professional electrician to touch anything hardwired).
    - 4y ago
Thrymr 4y ago
We _could_ even have standard DC bulbs for lamps with built-in standard power supplies, but they don't really exist.
Eddy_Viscosity2 4y ago
I wondered for a long time why we don't have standard built-in DC in building codes that could power our lights, and most electronic devices. Really the few things in my house that require full line voltage are all in the kitchen. Everything else has a transformer attached.
- Smoosh 4y ago
  Me too - standard 12V and 5V rails run throughout the house would be great. I even thought about a wallpaper with conductive strips so the power could be invisibly delivered to any part of any room and "tapped" with a push-into-the-wall socket.
  - xpe 4y ago
    The usual counterargument is: voltage drop can become a problem. Trying to use one big power supply and use DC as your only distribution mechanism probably isn't a good idea. But choosing a DC system for part of the house can make a lot of sense. For one residential new construction room, it can be practical to have one shared power supply rather than one per LED. Say you have a 12 V, 5 A DC power supply. Using a star wiring topology, this can serve 10 lights (at 500 mA) fine with 16 AWG.
    - djbusby 4y ago
      But how far can the power go before wire resistance causes too much Vdrop? Maybe one good transformer+rectifier per room? AC to the room and DC in the room. Those DC runs would be <5m each.
  - thrashh 4y ago
    The wires would be thick asf Not practical
  - lazide 4y ago
    Even 12V over 50ft+ will have noticeable voltage drop unless you have huge wires. 5v? Not even worth considering. And switch mode power supplies are relatively inexpensive and quite efficient.
midoridensha 4y ago
You can't have a low-voltage DC power supply supplying the entire home: the voltage drop between the supply and the LED would be huge. There's a reason we use higher voltages for long wire lengths: to increase efficiency and reduce line losses, since losses increase geometrically with the square of the current (according to Ohm's Law: P = R * I^2). Higher voltage means proportionally lower current, and geometrically lower losses. And since we need high voltage (at least 100V) to keep line losses very low and allow the use of thinner-gauge copper wiring, we need a switching power supply at every light fixture, so it really doesn't matter if it's AC or DC, since modern SMPS (switch-mode power supplies) work equally well with either. Finally, on top of all that, LEDs are current-driven devices, and need a constant-current power supply. So the power supply must be very close to the diodes, or else fluctuations in supply voltage will have very negative effects.
Xcelerate 4y ago
> A single home DC power supply with ~200W of output could light an entire house, flicker free. How about power over ethernet?
jrockway 4y ago
> This is the frustrating thing about LEDs that IDK we can change. I think that non-bulb LED fixtures are relatively common. For example, a style exists where you cut a hole in the ceiling and friction-fit the LEDs with the power supply up in the attic (presumably with infinite convective airflow): https://www.lowes.com/pd/Utilitech-Canless-Color-Choice-Integrated-LED-4-in-50-Watt-EQ-White-Round-Dimmable-Canless-Recessed-DownLight/1001771854 https://www.lowes.com/pd/Utilitech-Canless-Color-Choice-Inte... These power supplies aren't going to die from overheating because the power supply is nowhere near the heat-producing LEDs. And, it's not like $30 for your entire light fixture is going to break the bank.

petra 4y ago

Would this system need new electrical wiring ?

wlesieutre 4y ago
Yes. For the commercial DC lighting installations I've seen they were using power over ethernet. That's not necessarily the only way to deliver DC power but whatever you do it's going to be wired differently from 120 VAC.
- samtho 4y ago
  I used to do electrical installs in commercial buildings and this was starting to catch on, mainly because the the practice of running ethernet (including the 8P8C aka RJ45 connector, patch paneling, etc) is already established. This always felt very roundabout and requires expensive networking equipment just to run lights which I do not personally like because it will just cause confusion.
  - xxpor 4y ago
    You also get (the wiring for) remote control for free though, which is nice. It seems like there would be a market for cheap as possible 10 mbit switches with 802.3bt/802.3af support though. https://www.amazon.com/Gigabit-802-3af-100Mbps-250Meter-Unmanaged/dp/B0899MWYKL https://www.amazon.com/Gigabit-802-3af-100Mbps-250Meter-Unma... is pretty cheap as is, I'm sure you could buy something in bulk for cheaper.

JohnFen 4y ago

Low voltage DC lighting is a thing that has existed for a very, very long time. That most houses don't have it is more cultural than anything else, in my opinion. That means it's totally fixable. You can install such a system in existing buildings right now, and it's not crazy expensive unless you want to run the wires inside the walls. If we could shift cultural expectations around this, adding a LV system in new construction would not significantly increase the construction costs. It will start to be done if buyers start demanding it.

yencabulator 4y ago
For example: the stairwell shin-height lights in this 90s house are 12 VDC. There's a transformer plugged into a wall outlet in the nearby storage closet.
- midoridensha 4y ago
  That works OK because the transformer is relatively close to the lights. If it were a reasonably-large house, and the transformer were on the opposite side of the house, you'd have a problem with a noticeable voltage drop. All these ideas people are throwing out here involve a single whole-house power supply. If it were for 48VDC, it would probably be fine, but 12V would result in significant line losses.
  - yencabulator 4y ago
    We already see transformers for a run of e.g. track lights, low voltage lights on tension wires, and so on. That's been a thing ever since halogens came to market. Having multiple transformers is perfectly doable and commercially viable -- though I would appreciate more product availability for something easy to stash in the hollow space of a ceiling, like recessed lighting is installed.
    - midoridensha 4y ago
      I still don't see the point of all this. If you have a handful of lights in a room, and drive them with a single power supply, you're still going to have big problems: the line lengths to each fixture will be different, resulting in different voltages. You can't drive LEDs that way with good results: they need fixed current. And you can't daisy-chain them either: if one emitter dies, then the remaining ones will suddenly have different current, and probably die quickly. The proper way to drive LEDs is with a power supply very close to the emitters and designed specifically for those emitters and the (short) wire length to them, not 4 meters away and not with some variable-length wire that can't be designed for. Everyone here is complaining about ultra-cheap LEDs that don't last very long because they're poorly engineered, but that's exactly what you're all trying to do here by using a separate, shared power supply. You could get away with that in the 1980s using incandescent bulbs, but you can't do it now unless you want the same crappy lifespan and reliability you're all complaining about. The solution is very simple: buy fixtures that are engineered well. Switch-mode power supply electronics are not expensive at all, but when mfgs cheap out or do a crappy job designing them, you get bad results, usually short lifetime of either the power supply or the LED. What you're trying to do here is buy a really expensive power supply, which has to be engineered to a far greater degree and for a far wider range of operating conditions (since they don't know what you're going to connect to it), just because you had a bad experience buying some $2 light bulb that had a crappy power supply built-in. This really makes no sense.

bryanlarsen 4y ago

We've had 2 standard DC outlets for a while now: 12V cigarette lighter and 5V USB. You do often see them in odd places. But the voltage and wattage of those specs is too low to be useful, so they haven't evolved into DC power distribution. USB-C PD is at a useful voltage & wattage level, and so is Ethernet POE. I wouldn't be surprised to see them start to be used for general power distribution in niche applications, like RV's and off-grid cabins. I don't think we're going to ever get a bulb standard, though.

zaroth 4y ago
Cars are starting to move to 48V DC. My under cabinet lighting in the kitchen are powered by DC from a power supply in the basement. I could definitely see this becoming more common. Powering the ~100 watts of fixed lighting spread across my whole house on ten different 15A 120v circuits, each with their own arcfault breaker and 12 gauge copper electrical lines running back to the panel is fabulously expensive for what could be done with a bunch of CAT5 in each floor running to some conveniently located “POE injector” type devices. You would want to be able to take a standard fixture and just push DC through it and use special bulbs with a standard A19 base, but that’s problematic when the next owner tries to screw in a standard bulb - what happens when it sees 48V DC? I would guess if for safety reasons it has to be a non-A19 connector, then your light fixture choices get cut down to almost nothing and no one will make the switch? It’s really interesting to think about, most everything I’m plugging into AC outlets in my house, the first step is converting it to DC. A lot of my outlets I’ve switched to include USB ports so I don’t need the wall warts. If you have solar and battery backup even more-so you start to question why we are wasting so much money moving everything back and forth between DC/AC/DC within a house.
- garaetjjte 4y ago
  >screw in a standard bulb - what happens when it sees 48V DC? Either it lights up or not? I don't see a problem here. But I'm not sure moving part of power supply elsewhere will help that much, it needs current driver electronics anyway.
- pwg 4y ago

coryrc 4y ago

LEDs must be powered by a constant-current supply, and distribution does not work well at constant-current, and is always constant voltage. So no matter what you will need some sort of switching power supply. LEDs are like 15% efficient and power supplies are >95%. They just need to be separated slightly so the LEDs aren't heating the power supply. Most recessed LED lighting now has a separate junction box with the power supply.

samtho 4y ago
> LEDs must be powered by a constant-current supply, and distribution does not work well at constant-current, and is always constant voltage. So no matter what you will need some sort of switching power supply. I think the biggest problem is that many cheap power supplies cycle at lower frequencies that cause flickering which is perceptible subconsciously. A modern switchmode power supply might operate in the 50-500khz range which will not cause perceivable flickers.
- int0x2e 4y ago
  The really cheap stuff actually doesn't even have a power supply! There's a breed of LEDs that takes straight AC and rectifies it using the LEDs themselves. By using a large number of tiny LEDs in series (typically in COB form), you can easily reach close to 110v or even 220v, and then you add a small current limiting controller in series that's dirt cheap compared to magnetics... These are super cheap, and appear bright, but they flicker at 120hz, which can be annoying when there's motion or if you're sensitive to it. I'd say it's a very bad choice for a bedroom or living room light, but I have nothing against it for the outdoor lights, signage and a bunch of other applications where cost is king.
  - amluto 4y ago
    I have a serious problem with it for outdoor lighting and signage: it gives me a headache. Enough exposure will make me feel actively sick. The effect is not subtle. Just don’t use these devices, please.
  - 4y ago

samtho 4y ago

I am designing an off-grid cabin with a solar panel array charging a bank of batteries with a propane generator backup. I run ethernet as power with a custom designed PCB that terminates at the outlet side where it exposes a 20 watt USB charging port and an ethernet port. The lights are all basically cut 12v light strips inside of old light fixtures with a custom controller that also terminates PoE. The 48 volts that most PoE standards specify is more than enough to push power down the line for < 100 meter runs. The advantage of PoE here is that anything under 50 volts is considered low voltage and does not need to follow the same rules as normal house wiring. I did not like that everything is hinging upon a beefy PoE switch so I actually made it passive PoE instead by design.

int0x2e 4y ago
If you're willing to share your design, I'm sure there are other folks like myself who think this is a cool idea. I've wanted to do PoE (or passive PoE) for lights for a while now...
- samtho 4y ago
  I am going to open source it. The goal was to be able to get all the SMD stuff available at JLPCB so you can just send it to be fabbed (with some thru-hole components you would just solder yourself) or I would also sell them at cost + 10%. My brother designed some 802.3at chips and was going to have him review my work first as I don't want to send out into the world a poorly design power system (there are enough of those things out there unfortunately).
  - zulfazli 4y ago
    Cant see any github link in your profile. Any way I can get notified when you open source this? Thank you.
  - notjtrig 4y ago
    I'm interested in installing your design in my cabin as well, could also be very useful for boats too.

amluto 4y ago

I think this falls apart in the details. LEDs want constant current power supplies, and their owners frequently want them to dim. So you will still need a power supply. You can fudge it with resisters like in an LED strip, but you lose efficiency and dimming quality. That being said, I expect that power supplies with 48VDC input or so would be cheaper.

BizarroLand 4y ago
Maybe this could be a prosumer retrofit thing, where the AC voltage gets converted to DC in the junction box, and then DC is sent down to the fixture. Probably with some sort of current sensing system to make it compatible with dimmers. Pair that with DC A19 LED bulbs that have no internal power systems. Probably expensive to put together and to install, but if the goal was to have LEDs that last longer, that would do it.
- HideousKojima 4y ago
  >Maybe this could be a prosumer retrofit thing, where the AC voltage gets converted to DC in the junction box, and then DC is sent down to the fixture. The problem is that in 99.99% of homes outlets are on the same circuits as light fixtures, you would need to do some major rewiring.
  - BizarroLand 4y ago
    No, I'm saying you put a module into the junction box that the light fixture is attached to that serves as an AC/DC adapter, current limiting driver, and possibly a dimming sensor that would then provide downstream DC voltage to retrofit A19 bulbs. Those bulbs would then have no internal switching systems to burn out and rely entirely on the module hidden behind the wall to handle their power needs.
- xxs 4y ago
  You will see need to current drive the LEDs, DC alone won't help.

Zak 4y ago

Trying to cram all the infrastructure for an LED lamp into the shape of a light bulb is a bad idea, even if the input power is DC. Good designs for LED lighting have larger surface areas for heat dissipation and some physical/thermal separation between the LEDs and the power supply. A quality power supply does not produce flicker. As other comments have noted, dimming, or even predictable output requires some sort of power regulation even with DC input. I think the way to change it is to replace sockets with hardwired LED fixtures. This is easy for something like a standalone ceiling light. It may be harder for other devices like ceiling fans that integrate a light bulb socket, but converting those devices to take DC power as in your proposal isn't easy either (most would just get discarded and replaced). Doing it well is more expensive in the short-term than screw-in bulbs. A quick look on Amazon suggests integrated ceiling lights are about 10x the price of LED bulbs, though I suspect the longer service life pays for itself.

Joker_vD 4y ago
> Trying to cram all the infrastructure for an LED lamp into the shape of a light bulb is a bad idea, even if the input power is DC. Absolutely, the incandescent light bulbs have that shape for a reason: the screw is small because there is nothing to put in it and it doesn't heat, the bulb is large to dissipate all the light and heat it generates. And the LED light bulbs have exactly opposite problems: almost all of the heat is generated near the screw while the bulb itself generates almost none and the light-emitter doesn't even need the bulb that large around of it. Oh, and the casing around the screw is plastic so the thermal conductivity is horrible. Honestly, it's a profoundly terrible form-factor which we're now stuck with.
- Zak 4y ago
  I don't think we're exactly stuck with the old form factor. We can start phasing them out. Replacement of screw sockets with modern fixtures is well within the capabilities of the average DIYer (though perhaps some places it's illegal for anyone but a professional electrician to touch anything hardwired).
  - 4y ago

Thrymr 4y ago

We _could_ even have standard DC bulbs for lamps with built-in standard power supplies, but they don't really exist.

Eddy_Viscosity2 4y ago

I wondered for a long time why we don't have standard built-in DC in building codes that could power our lights, and most electronic devices. Really the few things in my house that require full line voltage are all in the kitchen. Everything else has a transformer attached.

Smoosh 4y ago
Me too - standard 12V and 5V rails run throughout the house would be great. I even thought about a wallpaper with conductive strips so the power could be invisibly delivered to any part of any room and "tapped" with a push-into-the-wall socket.
- xpe 4y ago
  The usual counterargument is: voltage drop can become a problem. Trying to use one big power supply and use DC as your only distribution mechanism probably isn't a good idea. But choosing a DC system for part of the house can make a lot of sense. For one residential new construction room, it can be practical to have one shared power supply rather than one per LED. Say you have a 12 V, 5 A DC power supply. Using a star wiring topology, this can serve 10 lights (at 500 mA) fine with 16 AWG.
  - djbusby 4y ago
    But how far can the power go before wire resistance causes too much Vdrop? Maybe one good transformer+rectifier per room? AC to the room and DC in the room. Those DC runs would be <5m each.
- thrashh 4y ago
  The wires would be thick asf Not practical
- lazide 4y ago
  Even 12V over 50ft+ will have noticeable voltage drop unless you have huge wires. 5v? Not even worth considering. And switch mode power supplies are relatively inexpensive and quite efficient.

midoridensha 4y ago

You can't have a low-voltage DC power supply supplying the entire home: the voltage drop between the supply and the LED would be huge. There's a reason we use higher voltages for long wire lengths: to increase efficiency and reduce line losses, since losses increase geometrically with the square of the current (according to Ohm's Law: P = R * I^2). Higher voltage means proportionally lower current, and geometrically lower losses. And since we need high voltage (at least 100V) to keep line losses very low and allow the use of thinner-gauge copper wiring, we need a switching power supply at every light fixture, so it really doesn't matter if it's AC or DC, since modern SMPS (switch-mode power supplies) work equally well with either. Finally, on top of all that, LEDs are current-driven devices, and need a constant-current power supply. So the power supply must be very close to the diodes, or else fluctuations in supply voltage will have very negative effects.

Xcelerate 4y ago

> A single home DC power supply with ~200W of output could light an entire house, flicker free. How about power over ethernet?

jrockway 4y ago

> This is the frustrating thing about LEDs that IDK we can change. I think that non-bulb LED fixtures are relatively common. For example, a style exists where you cut a hole in the ceiling and friction-fit the LEDs with the power supply up in the attic (presumably with infinite convective airflow): https://www.lowes.com/pd/Utilitech-Canless-Color-Choice-Integrated-LED-4-in-50-Watt-EQ-White-Round-Dimmable-Canless-Recessed-DownLight/1001771854 https://www.lowes.com/pd/Utilitech-Canless-Color-Choice-Inte... These power supplies aren't going to die from overheating because the power supply is nowhere near the heat-producing LEDs. And, it's not like $30 for your entire light fixture is going to break the bank.