For efficient downconversion of mains power to LED compatible currents you have to use inductors (either transformers or just straight through coils). Conveniently, the most compact and inexpensive inductive devices have to be run at very high frequencies (typically upwards of 100,000 times line frequencies) and then get filtered a bit with capacitors. Although the LED currents aren’t exactly smooth, the variation goes on vastly faster than biological photosensors can detect.
Which doesn’t mean that they’re all well-designed or well-made. Just that the line frequency doesn’t need to contribute visible flicker.
Sure, I was just responding to @Mike.71’s post that it’s possible to run LEDs off of mains power. Unless you convert to DC or a much higher frequency, as you point out, the flickering effect at 50 or 60 Hz AC mains is noticeable. To put it mildly.
The funny thing is that I learned the hard way not to feed the insects too much broccoli or cabbage/brassica type plants… Why? Because they make the room they’re in smell like the worst rotten egg fart for the next day. Short simple digestive tracts and all…
Color temp is important, but for best color rendering, look for a CRI > 90. CRI 95 is excellent, but increasingly hard to find as even high-end mfrs like Cree seem to settling for 90+.
(CRI is being replaced by newer, better scales, but it’s usually the only one reported at present.)
BTW, 2700K is good for mimicking standard tungsten bulbs, while 3200K mimics the more bluish-white halogen lamps. (Of course, many halogen lamps are over-spec’d on brightness, then cranked down with dimmers. That makes them much warmer, more like standard 2700K bulbs. LEDs generally stay the same color temp as they dim.)
5000-6000K LEDs are closer to real daylight, but they’ll usually look way too harshly blue-white for night-time illumination, because of the way the Purkinje shift changes your spectral sensitivity at lower night-time brightness levels.
This is what cheap LED Xmas light strings do - just string 100 1.2v. LEDs in series, and drive 'em directly with 120v/60Hz mains current.
Which is why they flicker horribly. And, yeah, they’d be totally unsuitable for general indoor lighting.
(Somewhat more sophisticated sets add a bridge rectifier. They still flicker a bit at the AC voltage zero-crossing – a very brief dark flicker at 120Hz, rather than the cheapies’ 60%-duty-cycle blackout at 60Hz, so it’s way less irritating. Good LED bulbs even smooth that flicker away, usually with L-C filters.)
Would that involve thicker copper wiring? On the one hand lower voltages mean more resistance losses with the same gauge wires, on the other hand, lower wattage implies lower losses. I’m not sure where the balance is.
If it’s for lighting, no. LEDs are lower voltage and lower current. If we’re talking about new general purpose sockets then yeah I think (power = voltage * current, 1/10th the voltage means you need a lot more current for the same power.)
This. However, it might require coax or twisted pairs to keep ground loops from transmitting low frequency or harmonic EM in your lighting. Or, it might be something that can be smoothed out in the lamps themselves with some simple circuitry.
Since incandescent bulbs are almost pure resistance, even with AC you can use the Amps X Volts = Watts formula, so a 100 watt bulb fed by 120 VAC will draw 0.833 amps. An equivalent (light output) LED fixture will draw about 15 watts. If that was fed by 12 VDC the amperage to the fixture would be 1.25 Amps, so it is higher but probably you would still use 15 amp circuits, since 10 fixtures on a circuit is a lot.15 amps will need 14 gauge wire.
Now if you have a 1200 watt toaster on a 12 VDC circuit, that would be 100 Amps, and that would be 2 gauge at the minimum. You would then need a separate 120 VAC and 12VDC circuit ran throughout your house. and that’s a lot of extra wire. The upside is instead of having a lot of inefficient (cheap) 120 VAC to 12 VDC rectifiers all over ,you would have one much more efficient power supply somewhere.
So it probably makes sense for an office or factory building. Certainly running a higher voltage circuit for fluorescent lights was fairly common at one point in some applications
Yes, most office lighting circuits in America are still 277 VAC (one leg of 460 to ground), so they can put more lights on each circuit. Most mechanical systems in commercial applications are 480 VAC 3 phase.
