![]() 220v LED bulbs are becoming cheaper and cheaper. Your next question would be capital vs ongoing. If you are talking offgrid then that is a different concept to using off the shelf technology that is a replacement for 220VAC. If you really want DC then 36-48v is optimum and most of the PV panel providers would agree. ?ġ2v is not a good voltage for anything DC in a house, it just happens to be a standard that’s been around for a while. The question here is what are you trying to achieve. If I was going PV from day one it would be an easier decision to use 12v LED from day one. I suppose the answer would be to added in a lithium iron battery and selectively charge from mains when battery voltage drops but now things are getting complicated. Would this also apply to upmarket gear as supplied by Victron Energy? The offgrid preppers would not tolerate such background wastage but I guess you are referring to the 240vac/12vdc function when enabled with zero load. range hob illumination, lights above work surfaces, under wall cupboard lighting and pendants over the island. Based on my current kitchen I would want 4 switches for manual mood arrangements e.g. In this example I would not want everything controlled by a single switch. Running the same LEDs on 12V DC fixed the problem, and they barely run warm. The result was that they overheated and would eventually either smoke or unsolder the SMT bridge rectifier from behind the circuit board. The reason was that these put out 12 VAC at around 20 kHz, and the bridge rectifiers in the MR16 LEDs weren't capable of switching that fast, as they didn't use fast recovery diodes. ![]() One thing I did find was that the multiple 5050 LED MR16s were not happy when driven with the small "electronic transformers" intended for normal halogen MR16s. It's not the most efficient system, but the total losses aren't that far off those for a typical cheap switched mode supply. The LEDs were run at between 20 and 30 mA, so the dropper resistor only had to lose between 1.8V to 0.7V. The bridge rectifier included two diode Vfs of around 0.6 to 0.7 V each, so increasing the voltage required to around 10.2 V to 11.3 V. ![]() IIRC, the Vf of the white LED varied from around 3V to 3.3 V (with current and colour temperature), and they were wired in banks of three in series, giving 9 to 9.9 V to drive them. They were free of any interference generating elements, too. There were small losses across the resistor and diode Vf in the rectifier, but these were modest, and little more than a cheap switched mode regulator. Add that up for 24v hours a day, 7 days a week, and it's apparent that it's quite a bit of wasted power, especially if the supply is rated for the whole house, or even just a single floor in the house.Īll the many MR16 samples I obtained just used an array of series/parallel connected LEDs to get close to 12V, plus a bridge rectifier (because the 12 V downlighter spec is 12 VAC) and a very low value dropper resistor. Even a really good switched mode supply may draw around 5% or so of it's rated power just when powered on with no load. The other problem is the vampire load from the power supply. I doubt the switch would last long switching 5 A DC, but more importantly, it has no certification for use at DC, which could cause problems in the event of something going wrong. I had to add supplementary LED strips under the wall units to get an adequate light level on the worksurfaces, and they add an addition load of around 12 W, so if I'd used 12V DC switched supplies then the wall switch would have been handling a total of around 60 W, or 5 A. I have a total of 48 W of LED ceiling panels in our kitchen, and that's marginal, in my view. You may well get away with one running a very tiny load, like 4 off 3W LEDs, but you will need a lot more LEDs than that to light a room well, especially a kitchen or utility room. The snag is that wall switches are not designed to switch DC at all, as they have really slow to operate contacts. If so, surely a light switch capable of handling 750 watts and the sparkiness of 240 volts and the dangers of AC, will cope with the 12 watt draw of 4 x 12 volt DC LED ceiling lights. At this point is it reasonable to conclude 50% loss in the embedded rectifier? The more I learn about their design it is surprising these do not cook and blow within 5 minutes. +700 watts per wall switch.Īt the other end of the scale a 60w (lumens equivalent) LED draws 6 watts including losses for some lashup of semi rectified cheapo circuitry embedded within the light. If a home is wired for current 240v ac lighting standards then I guess the circuit is good for 3 amps i.e.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |