How to choose LED bulbs

[ericmark]

I have a folded fluorescent lamp 11W above my computer is a table lamp the lumen per what is about the same as for my LED lamps however it does not mean all LED or all fluorescent will produce 100 lumen for 1.4W the light output varies rather a lot.

The GU10 is a silly spot light but great for reading lamps so use them in bed room and in table lamps. I looked into these bulbs and also the 12 volt version GU5.3 and it would seem with the 230 volt version a switch mode power supply is used to reduce the voltage to around 3 volt needed for a LED. But with the 12 volt version often this is not the case and a simple resistor is used. If you look at the GU10 it is limited how many LED's can be used in the bulb as having 80 LED's in series and simple resistor is not an option.

Look at this

bulb and like with 12 volt GU5.3 the manufacturer could put 80 odd LED's in series and use a resistor.

The resistor produces more heat than a switch mode power supply so Lumen per watt would be less. Where lumen is given as well as watts you can work out the efficiency of the bulb but any chart like this

will include tungsten so rather useless to compare one LED against another. (chart was really for a boiler).

When I wanted a LED bulb for the caravan I wanted to check the voltage range and for a GU10 bulb you could find info 150 - 250 volt was common but for 12 volt no such range so this points to switch mode regulation with 230 volt types and simple resistor with 12 volt types.

Fluorescent is no better the high frequency ballast for my 18W light at top of my stairs is likely to use far less power per lumen as using the same tube in a fitting with a wire wound ballast and this is the big problem. Control gear and lamp may be combined but they don't have to be combined so taking that 18W lamp there are three independent factors controlling the light output.
1) The plastic cover
2) The type of fluorescent tube
3) Control gear used
All made by different manufacturers and the selection can mean one set up give up to 4 times the output of another set up. Even with lights using a simple bulb there is often a shade or globe around the lamp specially now peal lamps can be bought in tungsten so one bulb measured in a fitting with connection to bottom compared with another may show first bulb as better but use a fitting with connection to top and this can be reversed.

We have seen government attempts at miles per gallon and fridge/freezer comparison charts and in both cases it has gone silly with car manufacturers publishing 250 miles per gallon on a hybrid car where really the figure should be 40 and the demise of the 40/60 fridge/freezer because manufacturers need to show A+ and the calculation method makes it very hard to reach when freezer is larger than fridge. So now many families have stand alone freezer as well as fridge/freezer because of government intervention.

To require lumen and watts on all bulbs is really enough. The problem is of course still the lumen. With a bulb rated 150 - 250 volt which clearly used a switched mode power supply watts and lumen will remain static.

But 200.79 volt to 253 volt (the range a lamp can expect) with a tungsten bulb or a fluorescent with wire wound ballast the watts to lumen will vary to quite a high degree with some fluorescent 100% where it just fails to work at 200.79 volt. So if in your house volts are 253 the max permitted then swapping tungsten to LED likely LED will look dim although will last a lot longer but if your house volts are 201 the min permitted then the LED will look far brighter than the tungsten it replaces.

With wire wound ballast the fluorescent is really a problem I did tests with a 110 volt 60W and at 127 volt it was 0.8 amp but at 110 volt 0.6 amp (it was the two options on the transformer) if the power factor correction capacitor was disconnected it went to 1 amp with no noticeable difference in output of tube. So in watts 66, 101.6 and 127 so not quite double but well over 1.5 times the power for same output with just a 17 volt difference in voltage.

Lucky the rules for car head lights are more stringent this includes how lumen is calculated the light has to have been on for a set amount of time before it is measured. Also of course every MOT it is tested then the test gear measures light output not watts.

 

[Ronob]

Well, I decided to take the bull by the horns and buy one BC22 60w equivalent bulb to see how it goes and I have to say I am a lot happier than I thought I would be.

It cost me £7 from Wilkinsons (own brand) and is 10w rated at 810 lumens which the box said was equal to 60w. As an ex-photographer, I still have my trusty light meter, so measured the light from the tungsten bulb it was replacing and then from the LED and is was actually quite a bit brighter! - I didn't need the light meter to tell me that, it was noticeable when I switched it on! And the light is pretty well scattered evenly too.

Sadly, I also noticed whilst going through all the tungston and halogen light bulbs I seem to have acquired, that the bulb I just replaced came from a carton of 10, remember when light bulbs were in a corrugated card wrap? Well this carton was a pack of them Mazda and had a price tag of £2.75 - 27p each so the £7 hurt a little after seeing that!

 

[big-all]

you save around 1p per watt per week on an average 10 hrs on per day and around 14p a unit
so your saving around 50p a week if it averages 10 hrs a day or 70hrs a week thats £26 a year does that ease the pain

 

[Ronob]

OMG! As the young people might say, I have now discovered another problem with LED bulbs - having read further into these blessed things it now appears that LED bulbs have heat issues and 'which way up' issues!.

I thought I might put one of these 8w bulbs in the outside light next to our front door (coach style light) but from what I've now read this could be positively dangerous! Because of the lack of air circulation around the base of the bulb!

Secondly the article on heat also pointed out that I have to be careful that bulbs I purchase for wall fittings etc. are compatible with being used upright or down facing! - is this a joke?

It seems buying a light bulb is becoming more complicated than trying to calculate UK postal rates or train fares. And Bernard (if you are stil viewing this thread) do you really think it s the consumers job to search out this kind of important information prior to purchase? Would any 'normal' consumer even think about whether to ask the retailer if the bulb can sit in an upright holder? Would the retailer know? Why isn't this on the box?...... I won't even begin to mention anything about the 45 degree temperature operating ideal!

 

[big-all]

i have had several fail over the years non have been "dangerous" they just stop working properly

i would expect something like a 4w bulb would be enough for a background light
or you could remove the glass nearest the wall for ventilation
if the 8w bulb is not on for more than an hour at a time the risk off failure will probably be small
i have 2 x4.5w corn type in my bathroom fully enclosed and they are on fairly constant often 14-15 hours at a time and they are approaching 8 years old

 

[bernardgreen]

And Bernard (if you are stil viewing this thread) do you really think it s the consumers job to search out this kind of important information prior to purchase?

Yes I do.

At the risk of upsetting a few people I will say that the general public have in the past few decades become lazy and want everything handed to them on a plate without them having to do any thinking or research about what they are going to buy. A lot of this is due to the way things are sold. Too often this depends on the customer's ignorance ( lack of necessary knowledge ) about the items they are buying. Some sales people will say whatever the customer wants to hear in order to make the sale.

 

[Ronob]

Oh Bernard, you crease me up!

We are talking effing LIGHT BULBS! It should not be rocket science. Name me a consumer who might even think of asking if a light bulb can be put in an upright holder! You simply shouldn't need to undertake such extensive research to buy a light bulb especially when we are all being encouraged to buy low energy bulbs.

Interestingly, I have just searched the website of my energy supplier who makes no mention of LED bulbs in confined spaces or of their orientation but does actively promote their use (even sells them).

 

[Hysteresis]

Let's introduce yet another problem to the LED debate.
When my house was built the Kitchen unit downlighter were installed using 12 MR11 Halogen down lighters. So I bought 12v LED MR11 'bulbs' to replace the Halogen bulbs. No problem there one would think, WRONG.
The Halogen bulbs were installed using some Electronic transformers specifically designed apparently for Halogen lights. Just why Halogen lights need a specifically designed electronic transformer is beyond me after all Halogen lamps are Incandescent Lights with a Halogen gas introduced into the glass envelope so there is nothing electrically special about Halogen lights. Never the less I have 3 Electronic transformers installed to supply the 12v to the 5 down lighters.
The resulting operation was very confusing, One circuit worked another worked for a while then switched off with a click from the transformer. The third circuit wihth only one downlighter would work some times but refused to illuminate until the switch was turned off then on immediately.
Research concluded that Electronic tranformers are not always suitable to operate LED's but sometimes they are. I though the problem was Low Loading on the Transformer with only one down lighter so Iwired up 3 downlighters to one transformer, and thought I have cracked that problem. But oh no I didn't. After the lights were on for 30 minutes the three lights went off with the characteristic click from the transformer. I left the power on and hey presto the three lights came back on with a click once again only to go off after a couple of minutes and this cycle continued. The click and resulting cycling seemed to be the operation of some thermal overload. Just why there should be a load? thermal problem is beyond me as the transformer originally supplied 60 W load and now I was only asking it to supply 18 watts, so any thermal problem should not be evident.
Being a 'Smart Arse' I thought if it were a thermal problem I will remove the Electronic transformer from its plastic case to improve the cooling effect. That had no effect what so ever to the switch off cycle after 30 minutes. SO the thermal theory was another failure in my thinking.
SO I have now reverted to Tho LED's on each of two transformers and one on the third transformer and Accept that I occasionally have to double switch the lights on to get all LED's to operate.
I thought I would see what is so special about Electronic Transformers and I would not recommend that route. I have a degree in Electrical Engineering and what I read confused me completely as there are so many variations of electronic transformers that it would require a lot of detailed study to start to understand them. Just why Halogen lights should have electronic transformers is beyond me and why electronic transformers may not work with some LED's is further beyond me.
In my ignorance I assumed an electronic transformer was an electronic circuit that initially used a Bridge rectifier producing a smoothed DC supply followed by some form of potential divider followed by an Inverter circuit to produce the requited 12v AC. This is not the case and an electronic transformer still used the Wound Magnetic properties of a conventional transformer followed by some circuitry to effectively isolate the supply from the load and the design is only to facilitate the use for electronic circuits, so totally in appropriate for the supply of an incandescent/ resistive load.
So in conclusion replacing 12v Halogens with 12v LED's amy or may not work sometimes and may work at other times. Answer replace the 12v downlighter with 240v GU10 fittings and throw the electronic transformers in the Bin.

 

[Ronob]

Oh f*** it! If a bloke with an electronic degree can't figure it I give up!

I'm buying a paraffin lamp!

Anyone know where I can buy paraffin these days, do I need different wicks for pink and blue paraffin? Do I get a higher lumen rate from blue than pick paraffin?
Questions questions!

 

[Hysteresis]

Oh f*** it! If a bloke with an electronic degree can't figure it I give up!

Read again Robnob - I said an Electrical Engineering Degree NOT and Electronic Degree, and believe me there is as much difference there as there is between a Theoretical Physics Degree and a degree in Physical Astronomy.

 

[bernardgreen]

The electronic transformers are in truth a Switched Mode Power Supply ( SMPS ) and those for halogen lamps produce the correct voltage for the lamp, But very often it is not a steady state 12 volt. It can be 24 volts switched ON and OFF at high speed such that the AVERAGE applied to the lamp is 12 volts. Works fine.

12 volt LED lamps have an LED driver inside them to control the current through the LED element. not the voltage but the current.

The LED driver is also a form of SMPS and often control the current by pulsing it.

The reason for the instability when a 12 volt LED is supplied by an SMPS designed for halogen lamps is the pulses of voltage from the halogen SMPS confuse the LED drivers pulse generation. ( simple description of a very complex interaction between two SMPSs )

 

[big-all]

i don't actually worry about bulbs failing buying another dosent worry me
all i know is maximum lights on = around £18 a year
spend time and effort worrying and turning them off will save a maximum off around 1/3 or £6
i simply don't bother worrying for £6 a year 50p a month 12p a week or 2p a day

 

[Ronob]

Oh f*** it! If a bloke with an electronic degree can't figure it I give up!

I'm buying a paraffin lamp!

Anyone know where I can buy paraffin these days, do I need different wicks for pink and blue paraffin? Do I get a higher lumen rate from blue than pick paraffin?
Questions questions!

Sorry, I do know the difference -one is studied in room 23 the other in room 34 it's the old astronomy v astrology thing!

 

[Hysteresis]

The electronic transformers are in truth a Switched Mode Power Supply ( SMPS ) and those for halogen lamps produce the correct voltage for the lamp, But very often it is not a steady state 12 volt. It can be 24 volts switched ON and OFF at high speed such that the AVERAGE applied to the lamp is 12 volts. Works fine.

12 volt LED lamps have an LED driver inside them to control the current through the LED element. not the voltage but the current.

The LED driver is also a form of SMPS and often control the current by pulsing it.

The reason for the instability when a 12 volt LED is supplied by an SMPS designed for halogen lamps is the pulses of voltage from the halogen SMPS confuse the LED drivers pulse generation. ( simple description of a very complex interaction between two SMPSs )

That helps me a lot Bernard, Thanks.
It helps me appreciate the incompatibility of Electronic Transformers and LED Lamps, but there is still a weird effect which is not repeatable. When problem solving I look for changes and consistent effects. In this scenario I get different effects at different times and inconsistency in the effects of changes. If the electronic Transformer is incompatible with the load then it should either work or not. In this situation it works sometimes and not others even without applying any changes. At the moment I appear to have a thermal overload causing a trip which resets as it cools down but increasing the cooling effect on the Electronic transformer does not resolve the problem, so I conclude it is not a thermal trip I am getting although it gives exactly those characteristics.
I cannot understand why the original installation utilised Electronic transformers for incandescent lights, I would have thought is more cost effective just to have a simple 240/12v transformer with overload protection. I think LED lights would work OK with a simple 12v 50Hz supply as all of the necessary electronics to drive the LED's is integrated with the unit.
The problem with the industry is that the customer is not aware of the Electronic Transformer/LED incompatibly and this should be highlighted to any potential purchaser.

 

[Ronob]

i don't actually worry about bulbs failing buying another dosent worry me
all i know is maximum lights on = around £18 a year
spend time and effort worrying and turning them off will save a maximum off around 1/3 or £6
i simply don't bother worrying for £6 a year 50p a month 12p a week or 2p a day

You are failing to recognise the number of polar bears you are killing!
At least that's what the government and David Attenbourgh tell us. Furthermore according to a bold statement on a LED lighting retailer's website, I could save about £40 a year so in your case you might even get paid to put your lights on