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Post by cye on Nov 3, 2012 14:42:51 GMT -5
here's a (limited) comparison i did between a chinese 1.5w MR16 12v bulb (with 47 leds) and a saxby 1.5w MR16 12v bulb with just 20 leds inside. the first photo is the chinese one... Attachments:
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Post by cye on Nov 3, 2012 14:50:01 GMT -5
this next photo is the saxby one (both bulbs were pointed in exactly the same position for this comparison). you can see the chinese one is brighter in some places and darker in others. with leds being fairly directional, the uneven spread i guess is coming from the way the leds are glued into the bulb? the saxby is a much heavier affair made of solid glass and metal. i would say the glass in which the leds are embedded acts as a lens perhaps. the light is more evenly spread. whilst my perception of brightness may not be very scientific, i'd say they were both about the same brightness overall, but the saxby, being a more even spread, is a more usable light. not bad at £2/bulb. saxby is rated for 50 lumens per bulb. i can't find a rating for the chinese bulb. the most efficient CFLs in say 10w, are about 50-60 lumens per watt, so a CFL may in theory be more efficient. however, with leds being more directional and readily available in much smaller powers (e.g. 1.5w), one can easily point a led light where it is needed. mr16 led bulbs also run off 12v dc which is why i am interested. my plan is to have all rooms in the house rigged with 12v leds, with separate 12v cabling. the lighting can then be powered with either a 12 transformer or from a solar-charged battery. another benefit of 12v lighting cabling and led lighting is that both the cabling and the led lamps can operate under thick insulation quilt without any overheating concerns. by having a few leds in place of one larger cfl i think one could cut energy consumption substantially without compromising light where it's needed. 12v LEDs therefore have the potential to not only reduce electricity consumption, but also make it easier to deepen one's ceiling insulation and save on heating costs. A third potential advantage is that, for us urbanites, it gives us a practical and very visible application for small scale PV : An average house could potentially be lit with a max power of 20-30w during the hours of darkness, well within the capability of a small scale PV system. Attachments:
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Post by caveman on Nov 4, 2012 8:34:14 GMT -5
I have the bedrooms and some reading lights running on 12V LEDs. Would it make better sense to use CFLs for general lighting, and run them from an inverter and keep the LEDs for spot and task lighting?
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Post by cye on Nov 4, 2012 16:42:09 GMT -5
yes, i guess it depends on the space and how it will be used.
we have a hallway now lit very well with 3 X 1.5w leds. much better lit than it was with a single 10w cfl. maybe that's because the hallway long (ish) and thin.
same goes for the stairwells if one can be bothered fitting leds at regular intervals. as you say the cfl is probably better technology for general lighting in broader spaces. i've heard some folks point their leds up to white ceiling to get a bit of a better spread. then there are the new led 360 degree bulbs which are specifically designed to cater for general lighting, but they still won't have quite the same lumens per watt as the cfls and so cfls will be more efficient for large area lighting.
there are drawbacks with cfls. in the 20 years we've been using them, not a single bulb has lasted the length of time the advertising suggests. they also get dimmer with age. on the up side, the cfl warm-up time doesn't seem to be as bad as the early ones used to be and warmer light colours are available. then there is the mercury issue with cfls - if you break one then you must hold your breath, open a window, and leave the room for a while! i've heard nasty stories of folks cutting themselves on a broken cfl and the mercury making the lacerations hard to heal.
caveman, you know a mod for a cfl to make it run on 12v?
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Post by caveman on Nov 5, 2012 12:08:19 GMT -5
Not a CFL. They have their own switched mode power supply and are resistant to bodging. The only way I know of is to use and inverter to convert the 12v up to 230v. They are not too difficult to make but they do produce high voltages. There are many from 100w up available in the camping section of ebay., One of those could power the CFL load for the whole house, with them all on. I wonder how efficient they are at small loads, say when there a only a few cfls on? There are a number of simple circuits which will run small florescent tubes. There are ready built examples from caravan parts suppliers new and used but I think they are built to be lightweight with efficiency as a secondary consideration. They often have poor reflectors and lossy diffusers. I have gutted a few and used the connectors and little inverter to build into a better housing. Reading your last post I am reminded that I should be thinking about lighting more carefully. To think about what exactly the light is supposed to do. Is it general or task lighting? If it is a task how big an area needs to be covered and at what intensity. Will any shadows fall on the work? Might a reflected softer light be worth the effort? I am sure there are dozens of other useful questions.
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Post by horsall on Nov 5, 2012 15:18:27 GMT -5
Hello Both Has anyone used these people? I was thinking of getting 24v 9w CFL and possibly 24V DC 3 Watt LED Bulb as we have 24volt all over the house at the moment I use some 25volt industrial lamps(filament type) 25w and 40w
The 12volt versions would suit you
Roger
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Post by horsall on Nov 5, 2012 15:35:44 GMT -5
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Post by caveman on Nov 6, 2012 4:56:48 GMT -5
They look like the business. There is no reason why they ought to be any less efficient than their mains counterpart. It should be better than running a small single inverter at a fraction of its most efficient load. I could use the 24v versions here as the house is wired for 24volt with a center tapped earth. I wonder how long they last?
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Post by horsall on Nov 6, 2012 8:20:49 GMT -5
Hello Caveman In their blurb they say 8000 hours?
I think I will send for one CFL and one Led type.
We have no problem with 24volt as it is straight off the storage batteries and although the inverter comes on on demand 10/15watt it is useful to have a second lighting circuit in case of Failure,which happen last Boxing day about 11.30am just before all the family were coming to lunch the inverter melted its self, it was about 10years old and had been regularly overloaded(abused) with the mig welder and lathe and washing machine as it was only rated at 2.3KVA.
So there was I rewiring the engine shed so we could get the generator on, on the old inverter it went in and out off the inverter and there was no bypass switch.
The new one is all singing and dancing 3KVA with bypass switch built into the panel so only have to switch one out and one in.
The joys of living off grid
Roger
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