LED Downlights. GU10 vs MR16 - Page 1
Forum section: electronics / general

author: DrGeoff
author_rank: Frequent Contributor
timestamp: January 10, 2014, 12:50:53 am
content: Background: I currently have around 100 GU10 CFL downlights (11W) in the house. They are now about 3 or so years old and are tending to have reduced light output. I don't like them but was forced to install them when the new house was built due to Guvmint regulations.I've been trying out a few different GU10 LED replacements to see how they fare. I've found 9W to be suitable in some rooms and 12W in others. However several have not lasted, with power supplies popping within a few days of use, which is the reason for this topic. Can the little mains PSU's be trusted in the GU10 lamps? Particularly with hot roof conditions during summer. Or is it better to use MR16 bases instead and run a better quality 12V supply in the roofspace for each room?My preference for those rooms that have lights on all the time (I'm trialling them in the office, which has lights on at least 16 hours a day) to use MR16's. However some rooms only require lighting intermittently so GU10's might work OK, so long as the PSU quality is up to scratch.

author: peter.mitchell
author_rank: Super Contributor
timestamp: January 10, 2014, 02:45:27 am
content: Putting this out here;GU10 is just a bayonet mount designation and MR16 is just a dimensional designation of bulbs.MR16 bulbs and GU10 mounts have no fixed electrical design, components, requirements and ratings.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: January 10, 2014, 03:19:22 am
content: Just to clarify then:GU10 LEDs appear to be mains powered (90-265VAC) and MR16 all appear to be 12V DC powered.The GU10 is a bayonet fitting, all LED and CFL lamps I have seen with this fitting are mains powered.The MR16 is a 2-prong fitting, commonly used with 12V halogen lamps and also 12V LED lamps.

author: staxquad
author_rank: Frequent Contributor
timestamp: January 10, 2014, 03:19:31 am
content: try Switch, they're made to run coolerhttp://www.switchlightingco.com/technology.shtmlreview for Australian usehttp://www.popsci.com.au/technology/switch60-review-the-first-liquid-cooled-led-bulb-will-light-up-your-house-like-edison"SWITCH LED bulbs offer up to 40% better thermal performance than air-cooled LED bulbs."

author: peter.mitchell
author_rank: Super Contributor
timestamp: January 10, 2014, 04:11:27 am
content: Quote from: staxquad on January 10, 2014, 03:19:31 amYou might want to check out this;Also, Let me reiterate, MR16 is a bulb dimension designator, the "2 prong fitting" you mention is the GU5.3 base!So what you meant before was more like:QuoteSee how the GU10 vs MR16 did not make sense?

author: DrGeoff
author_rank: Frequent Contributor
timestamp: January 10, 2014, 04:23:56 am
content: I think you've completely missed the point here.The discussion was about the power supplies that are mounted in the LED downlight that have a bayonet GU10 fitting and are powered with 240VAC. They seem unreliable and could possibly be better replaced with the 2-prong fittings, as found in 12V DC halogen and LED lamps labelled 'MR16'. Is this clearer?The Switch bulbs are not even the correct fitting or type.

author: staxquad
author_rank: Frequent Contributor
timestamp: January 10, 2014, 04:36:28 am
content: Quote from: DrGeoff on January 10, 2014, 04:23:56 amthey've been delivered in Australia to hotels and other hospitality establishments since early 2012, so should be in shops by now with Australian fittings and voltage requirements.weren't you having trouble with longevity due to overheating?

author: staxquad
author_rank: Frequent Contributor
timestamp: January 10, 2014, 04:41:51 am
content: (sorry for my confusion, I thought MR16 were only GU5.3 and the MR16 GU10 were called something else)(Canadian Government is also dumping incandescents (like they dumped analog TV, commercial interests telling them to), but Led lighting is too early into development, and too expensive right now, will have to halve as far as I'm concerned, but then, would be glad to get rid of mercury toxic CFLs, where I'm located, the mines here won't install them for fear they break and stab someone to cause necrosis)http://www.liquidleds.com.aubesides 240V conventional led bulbs, they also carry MR16240V CREE GU10, not liquid cooled12 Volt MR16 CREE LED Cool White Narrow Flood Lamp - not liquid cooled but probably cooler than GU10 without power supply attached

author: DrGeoff
author_rank: Frequent Contributor
timestamp: January 10, 2014, 05:00:06 am
content: Quote from: staxquad on January 10, 2014, 04:36:28 amI checked the link given below and looked at the product line. They are all ES types.Quote from: staxquad on January 10, 2014, 04:36:28 amNo, I have not made any assumptions about the failure modes, just that they do fail. It could just be poor quality power supply design in these 240VAC LED lamps. Hence the discussion about using a single larger PSU per room, feeding 12VDC LED lamps, rather than the small PSU's in each 240VAC LED lamp.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: January 10, 2014, 05:07:18 am
content: Quote from: staxquad on January 10, 2014, 04:41:51 amNice quality downlight bulb!Would certainly be worth a trial , but they are a bit pricey at $35 a pop.

author: SeanB
author_rank: Super Contributor
timestamp: January 10, 2014, 06:30:15 am
content: I will recommend using the 12V versions, and get a magnetic transformer to drive them. This will give the best life. The most common wide range power supplies on the GU10 lamps suffer from being both crammed into a small space and from running very hot with very little margin. the GU5.3 12V ones are simpler, and have a larger value capacitor in them to provide better DC performance.Electronic transformers are not recommended, unless you just run them off a 13.8V DC power supply which can then be a SMPS. Major reason is noise and radiated interference.I have seen many of the 220VAC ones fail in a very short period, often the lower power ones use a capacitive dropper to drive the internal lamp electronics, or use a very low value capacitor that fails open circuit in a short time. The 12V ones mostly fail from being overrun from an electronic ballast that provides a waveform that can run a 12V incandescent lamp as it is a 20V pulse with a narrow width that the lamp integrates, but the electronics rectifies this and runs on 20V and dies after a while.My experience with the mains powered lights is they have a much shorter life compared to the 12V versions. only extra cost is the mains 50Hz transformers you will have to buy, but they are pretty cheap when you go to a lighting wholesaler and get proper transformers. 20 years life on them so far at work, on 7 days a week running pretty hot in the roof space in a pile to get 2kVA of capacity for the lighting. Slowly changing to LED one lamp every few months.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: January 10, 2014, 06:42:57 am
content: Quote from: SeanB on January 10, 2014, 06:30:15 amThanks for the advice. This was my hunch too, good to hear it from someone who has tried it.I'll do each room on a separate PSU, since the room light switches will be switching mains AC, as they do now. A regular room with 4 downlights should be able to be done with a 60VA DC supply. The roof space does not get too hot, thanks to the extra layers of insulation.

author: SeanB
author_rank: Super Contributor
timestamp: January 10, 2014, 07:15:29 am
content: As the insulation is likely on top of the ceiling sheets you will need to clear it away from around each fitting for around 10cm so as to allow cooling of the back side. This if not done will cook the lamps, and with halogen downlights has been known to cause quite a few house fires.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: January 10, 2014, 07:31:42 am
content: Quote from: SeanB on January 10, 2014, 07:15:29 amThe roofing insulation design I did for this house has a thick sarking blanket between the roofing and the truss tops, which keeps the roof space quite cool. It doesn't get above 40C even in the middle of Summer. An additional thick insulation layer on the ceiling plasterboard helps prevent heat escape during Winter, and these are cleared well away from the existing CFL light fittings to allow air flow.

author: kripton2035
author_rank: Super Contributor
timestamp: January 10, 2014, 08:04:20 am
content: I'm back to GU10 after some years of mr16.yes they are more subject to premature death of power supply part, but they are quite cheap to replace nowin fact the problem with mr16 is that you need thick and good quality wires because they need to support more amps than gu10and they get dry after one year and the plastic around breaks apart easily.just my 2cts.

author: SeanB
author_rank: Super Contributor
timestamp: January 10, 2014, 08:14:09 am
content: LED variants only need a low current wiring scheme, so you do not have any difference in wiring cost. The plastic parts are the first thing to degrade, but that is only on the cheap ones.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: January 10, 2014, 08:44:14 am
content: The thickness of wiring is really no different than regular mains wiring for the GU10 fittings. They have to be a certain size for lighting circuits according to the wiring standards. A 12W LED light will only require an amp, so regular fig-8 24/0.20 cable would suffice for each fitting.Are the plastic parts breaking because of heat? I've seen 50W halogens do this, where the contact would oxidise and create a hot spot due to the increased resistance. Would this happen with LV LED fittings?

author: djococaud
author_rank: Regular Contributor
timestamp: January 10, 2014, 09:45:11 am
content: For what I've seen from led bulbs, the GU10 lamps PSUs are often crap (due to the low space available, they use small capacitors and the less components as possible, and no surge protection).The fact that the PSU is just above the LEDs in a confined environment doesn't helps (the bulb is often placed upside down, wich is not thermally ideal)I would go with good quality 12V bulbs (the ones with integrated DC/DC current regulator) and power the whole room with a MeanWell RS-150-12 (pretty good quality PSU).

author: steve30
author_rank: Frequent Contributor
timestamp: January 10, 2014, 07:49:32 pm
content: I've been using some Philips CorePro GU10 5W lamps for a couple of months. They seem to be working nicely and don't get very hot. Unfortunately I've not been able to take one apart to find out what circuit it uses. Also, they are used in an area which is fairly cool, so we'll have to wait and see what happens when it gets hotter in the summer.As far as I can tell, Philips do seem to put a bit of effort into their designs, so hopefully they should be pretty good.I can't comment on 12V lamps as I haven't used any.

author: SeanB
author_rank: Super Contributor
timestamp: January 10, 2014, 08:00:31 pm
content: Here is a few that have been taken apart.https://www.youtube.com/user/electronupdate

author: DrGeoff
author_rank: Frequent Contributor
timestamp: January 12, 2014, 12:30:31 am
content: I trialled 4 12W Wun-Hung-Lo LED lamps recently, all of which blew up within 2 days of use. The light output was very good (more than the 9W LEDs that I am also trialling), the colour was 'neutral white', probably about 5000K.The supplier was apologetic and made a refund, however I decided to open up and examine the failure in more detail. In short, the power supplies were under-rated for the LEDs used.There's a full description and photos here:www.axtsystems.com/dl2014/led_failure/

author: rolandpenplotter
author_rank: Regular Contributor
timestamp: January 12, 2014, 12:48:18 am
content: Quote from: DrGeoff on January 10, 2014, 12:50:53 amAside from the fact that Andy is the KING of blowing things up for entertainment, he is a very clever chap, and his most recent video may help you decide - it addresses your enquiry PRECISELY:

author: DrGeoff
author_rank: Frequent Contributor
timestamp: January 12, 2014, 02:28:09 am
content: Quote from: rolandpenplotter on January 12, 2014, 12:48:18 amDoesn't really address much, except the multi-chip LED lamps he has tried. It did not cover the LED lamps that use 3 or 4 3W LEDs, nor did it address the quality of the 240V power supplies. At this stage the quality of the 240V PSU is the issue.

author: rolandpenplotter
author_rank: Regular Contributor
timestamp: January 12, 2014, 03:35:18 am
content: Quote from: DrGeoff on January 12, 2014, 02:28:09 amOkayWas worth a go.

author: kripton2035
author_rank: Super Contributor
timestamp: January 12, 2014, 09:56:37 am
content: what I learned (forgot I saw ...) from him is that the electronics transformers have a minimum load to startso if you have a lot of these, simply replace MR16 halogens with leds and the transformer will not start.so one point for gu10.(if you have recent electronics 12v transformers)

author: SeanB
author_rank: Super Contributor
timestamp: January 12, 2014, 11:03:53 am
content: Quote from: DrGeoff on January 12, 2014, 12:30:31 amI did order the 7W 12V versions of those, they came branded HTTP Solar, but have a single large multichip module on the really poor heatsink. Tested one for an hour and measured, die temp was 100C. As I just wanted them for the led dies and the PSU board it was no problem to take them apart. Thanks to Frankie for getting them at a good price for me as well. Took the lamps apart ( really poor mounting using the plastic light diffuser to hold the die down on the thin aluminium heat spreader, and using a drop of compound to transfer the heat along with having a milled slot to allow the wires to get to the middle of the sheet to go through the hole) and used epoxy to attach the die to an old P4 heatsink ( no fan needed here with 7W of heat, it was only needed for the 125W it had before) and put the inverter underneath. Now runs at under 40C for both the die and the inverter. The nice thing is the inverter is actually a constant current source that provides IIRC 350mA to the multiple series LED dies under the yellow phosphor blob. want more light use more little blobs up to a point. I have some driving a single die at 1W and some driving a 3 die one at around 3W.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: January 12, 2014, 11:09:23 am
content: Nope. Current system is all CFL's, with GU10 240V fittings.I was initially thinking of switching these over directly by fitting LED counterparts. At first I determined that some need to be 9W and others 12W for the replacements (about the same as the current CFL's).I've trialled a few types, all with GU10 fittings and 3 LEDs (3W and 4W LEDs). The recent batch gave out good neutral light but exploded (document in previous post). Others have lasted over 6 months so far.After these ones popped I thought I'd ask if anyone had had any experience to compare whether using a single decent 12V PSU for a room, and 12V LED fittings was a better option than using 240V GU10 fittings with a PSU crammed in each (which can get hot) so as to get maximum MTBF for the lamps.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: January 12, 2014, 11:17:34 am
content: Good to hear about your measurements and retro fitting Sean.I had to retrofit some wall lamps because they were rubbish electrical/thermal design. These were twin fluoro wall lamps (2x18W) which I retrofitted with some really nice 12W LED strips. I have a document about that as well (http://www.axtsystems.com/index.php?option=com_content&view=article&id=88:radiathermal&catid=48:fixingstuff&Itemid=81) which shows why they were simply exploding after about 6 months use. Also a fire hazard.I'm kind of getting sick of having to debug and modify some of the crappy junk that is sold on the domestic market to be fitted into new homes. Honestly, there's more poorly designed rubbish out there these days and unfortunately it's not until after the failures start to happen that this is discovered.

author: SeanB
author_rank: Super Contributor
timestamp: January 12, 2014, 11:37:47 am
content: I can tell you why the lamp ballasts in that module failed. Very simply the original design was for 2 PL18/C integrated starter lamps running in series, with a magnetic 36W ballast in the centre along with likely a 4uF 275VAC PFC capacitor. Now they wanted electronic so placed in there a retrofit 2x18W ballast, and went to the 4 pin PL18/C so as to have the 4 wire connection. they did not read the datasheet for the ballast and that it must be mounted in a location where it runs at under 40C surface temperature, compared to the magnetic, with the allowed 80c above ambient to a maximum of 130C surface temperature allowed. Thus the ballast going bang.I would always though mount those LED bars on a thick aluminium strip which has been ground flat on one side, and use heatsink compound to transfer heat to the bar to help with cooling on a thin backing sheet. the LED solution though probably gives the same light output and about half the power use though.