Led downlighters flickering

[assegayer]

Hi guys,
Had a little job today where some led downlighters were flickering it was 3 out of about 15. I checked the voltages on the 3 which told me the transformers for each one are broken. Confirmed this by testing a working one which was a getting a steady 11.5 to 12v ac.

I was just wondering what possibly could have cause these three transformers to blow. There is no insulation or anything obvious causing them overheat. Was thinking maybe loose connections.

Relatively new build i woud say 5 years max
Any ideas?


Side note: i attached pic of transformer. Secondary ouput says dc however when i test on dc setting get nothing when i switch to ac i get a reading.

Also where do they sell some decent tranies with the same specs?

 

[rolyberkin]

6W LED Transformer for 12V Spotlights and Strip Lights from LED Hut - https://www.ledhut.co.uk/led-driver-transformers/6-watt-led-transformer-driver.html

They currently have a £10 off your order.

 

[assegayer]

6W LED Transformer for 12V Spotlights and Strip Lights from LED Hut - https://www.ledhut.co.uk/led-driver-transformers/6-watt-led-transformer-driver.html

They currently have a £10 off your order.

Thank you very much for your reply. The transformer for some reason as shown in the pic i attached says secondary is 23 to 38v dc does it make a difference..i know this may sound silly but when i measured i had to set my meter to ac to get a reading

 

[Midwest]

Its a profitable market making transformers/drivers!

 

[freddo]

The 23-38V means the unit is a constant current device, It will ramp up the voltage until the current drawn reaches the rated output of 250mA. This allows for a number of series connected LEDs to operate correctly, the AC output you measured may be because the output is pulsed DC or just not very smoothed.
I would be searching for a 250mA constant current 'led driver' as a replacement. Have you checked the LEDs? They are not as reliable as they are advertised.

 

[assegayer]

The 23-38V means the unit is a constant current device, It will ramp up the voltage until the current drawn reaches the rated output of 250mA. This allows for a number of series connected LEDs to operate correctly, the AC output you measured may be because the output is pulsed DC or just not very smoothed.
I would be searching for a 250mA constant current 'led driver' as a replacement. Have you checked the LEDs? They are not as reliable as they are advertised.

Thank your detailed response i definetly tried different bulbs in them and it still didnt work. Then measured the output from the fault tranies and cross referenced with the healthy trannies and it was significantly different,constantly fluctuating badly.

So it wouldnt really matter if i got ac ones ? Also are they really this expensive like £6 a piece?

 

[freddo]

No you need a proper constant current LED supply, AC will quickly do the LEDs in, a standard 12v lighting transformer will not work. What brand/model are the lights? This might do as a replacement.

 

[assegayer]

No you need a proper constant current LED supply, AC will quickly do the LEDs in, a standard 12v lighting transformer will not work. What brand/model are the lights? This might do as a replacement.

Okay just for my own info is so for all LEDs they require constant current trannies. I am sorry i am not to familiar with LEDS. And a small job has turned big. Thanks for the link

 

[freddo]

To run an LED directly requires a current limited supply or the LED will draw enough current that it will destroy itself. There are some LEDs that can be run from a standard (usually 12V DC) power supply, these will have the current limiting built into the light fitting, usually in the form of one or more series resistors. The fixed voltage setup is usually only used with low power LEDs such as those found on LED strips. There is some information here and here.

 

[assegayer]

To run an LED directly requires a current limited supply or the LED will draw enough current that it will destroy itself. There are some LEDs that can be run from a standard (usually 12V DC) power supply, these will have the current limiting built into the light fitting, usually in the form of one or more series resistors. The fixed voltage setup is usually only used with low power LEDs such as those found on LED strips. There is some information here and here.

How would you know how many mA the transformer should be rated at?

 

[freddo]

The same as the old one?!

 

[Silly Sausage]

Just strip them all out, fit GU10 lampholders and 230V LEDs.
12V lighting is a waste of time and effort, as is clearly shown by this thread.

 

[assegayer]

What i meant was if your installing from new how would you know how many mA it needs.. anyway i am ringing every electrical wholesaler and there all saying they dont have that type (250mA). Is there any alternative other then replacing them. Like is there no other driver that would work??!

 

[assegayer]

I would order online as last resort but they want it done quick

 

[Barry White]

Just strip them all out, fit GU10 lampholders and 230V LEDs.
12V lighting is a waste of time and effort, as is clearly shown by this thread.

Totally agree with above but it may not run well with a customer who has only "3 bulbs flickering"
The problem is you match the drivers to the leds then someone fits a different wattage or if shared drivers some fail. Then someone fits a halogen "well it fits"
That said I run leds 12v mr16 on the standard wirewound ac transformers 12v in my kitchen and bathroom for a few years recently replacing them with gu10s.

You may be better ordering online as gu10 is common practice now too many pitfalls with unmatched lights and drivers.

What type of lamp is fitted?

 

[assegayer]

Totally agree with above but it may not run well with a customer who has only "3 bulbs flickering"
The problem is you match the drivers to the leds then someone fits a different wattage or if shared drivers some fail. Then someone fits a halogen "well it fits"
That said I run leds 12v mr16 on the standard wirewound ac transformers 12v in my kitchen and bathroom for a few years recently replacing them with gu10s.

You may be better ordering online as gu10 is common practice now too many pitfalls with unmatched lights and drivers.

What type of lamp is fitted?

Led gu10s are currently fitted...so if a trannie stops working they have to go through this whole process of finding correct trannie?

 

[assegayer]

I am still quite confuses how will the lamp tell the difference between which trannie i fit. Would i not be able to fit a standard led driver and be done with it

 

[Richard Burns]

If the lamps fitted are GU10 base then they should not be running off drivers, they should be connected direct to 230V, therefore I think something is missing here.

An LED will take a certain current and if that current is exceeded then the LED will overheat and fail.

Therefore if you have LEDs designed for 250mA and fit a 350mA driver then they will be very bright for a short while and then fail.

If you worked out /measured how much voltage is required for the LEDs you have installed and got a constant voltage driver of that voltage (or less) then you may get away with it, but as soon as there is a variance in the LEDs, e.g. one fails, the others will cascade into failure.

Most LED constant current drivers are 350mA (or multiples thereof) so your 250mA LED driver is slightly out of norm.
Somewhere like RS, CPC, Farnell, Rapid would have these 250mA drivers and be able to get them to you tomorrow (maybe Weds by now).
If you are really stuck then you could try Maplin, if you have one near, who may have them if you want to overpay.

 

[assegayer]

If the lamps fitted are GU10 base then they should not be running off drivers, they should be connected direct to 230V, therefore I think something is missing here.

An LED will take a certain current and if that current is exceeded then the LED will overheat and fail.

Therefore if you have LEDs designed for 250mA and fit a 350mA driver then they will be very bright for a short while and then fail.

If you worked out /measured how much voltage is required for the LEDs you have installed and got a constant voltage driver of that voltage (or less) then you may get away with it, but as soon as there is a variance in the LEDs, e.g. one fails, the others will cascade into failure.

Most LED constant current drivers are 350mA (or multiples thereof) so your 250mA LED driver is slightly out of norm.
Somewhere like RS, CPC, Farnell, Rapid would have these 250mA drivers and be able to get them to you tomorrow (maybe Weds by now).
If you are really stuck then you could try Maplin, if you have one near, who may have them if you want to overpay.

Thanks a ton for the background info. They are MR11 LEDs. Looks like ill have to order them online then what a pitty. I never knew LEDS where this complex to be honest. Where would it say which rating of Ma is required . On the bulb it self? Packaging? For example if it was a new install and you were fitting them.

 

[assegayer]

If the lamps fitted are GU10 base then they should not be running off drivers, they should be connected direct to 230V, therefore I think something is missing here.

An LED will take a certain current and if that current is exceeded then the LED will overheat and fail.

Therefore if you have LEDs designed for 250mA and fit a 350mA driver then they will be very bright for a short while and then fail.

If you worked out /measured how much voltage is required for the LEDs you have installed and got a constant voltage driver of that voltage (or less) then you may get away with it, but as soon as there is a variance in the LEDs, e.g. one fails, the others will cascade into failure.

Most LED constant current drivers are 350mA (or multiples thereof) so your 250mA LED driver is slightly out of norm.
Somewhere like RS, CPC, Farnell, Rapid would have these 250mA drivers and be able to get them to you tomorrow (maybe Weds by now).
If you are really stuck then you could try Maplin, if you have one near, who may have them if you want to overpay.

Would something like this do

MW APC-8-250 - Power supply 16-32 V, 250 mA - https://m.reichelt.com/?LANGUAGE=EN&CTYPE=0&MWSTFREE=0&CCOUNTRY=447&ARTICLE=170876&PROVID=2788&wt_guka=22596714617_79177294217&PROVID=2788&gclid=CK2kwtrP0M8CFRQ8GwodG1gDPA

 

[assegayer]

Something like this wouldnt work right as its constant voltage and not constant current

POWERPAX - PLV2524-01 - 24Vdc, 250mA, 6W Constant Voltage Miniature LED Driver | CPC UK - http://cpc.farnell.com/powerpax/plv2524-01/24v-dc-250ma-led-driver-lugs/dp/PW02617?ost=250ma+driver&selectedCategoryId=&searchView=table&iscrfnonsku=false

 

[Richard Burns]

The one from Germany may well work it has the 250mA output however it is only a maximum of 8W whereas your original is 11W, so long as you do not need more than 8W this is OK.
The constant 24V one would not be a good choice but may work, since if you look at your existing driver the minimum voltage is 23V (max 38V) and so if the lamps were fed 24V it is unlikely the current would be too much, however there would be no control of the current and if you wanted a 9W supply then the driver would be overloaded as it is only 6W.

Now I have actually looked the 250mA ones are not common, most start at 350mA.


Lamps that require constant current should have printed on them a wattage and current rating and not give a voltage rating.
If they need constant voltage then they will have a wattage and a voltage rating normally for individual lamps this is 12V, LED strips can be 12,24,36,48 V
Generally LEDs are wired in series for constant current and in parallel for constant voltage.

Mostly assemblies of LEDs might be constant current but individual items are constant voltage. It is much easier to get a 12V driver for LEDs and make sure it can take the total wattage which is what you would normally have for LED lamps on their own.
You have the slightly more complex arrangement of a set of lamps.
However usually they would be 350mA for which there are hundred of suitable drivers out there.

For your application I am assuming this is a set of MR11 LEDs in a unit or something like that, otherwise I would expect them to be 12V items even for MR11.

MR11 is not GU10
This is a diagram of some lamp bases for comparison.

 

[assegayer]

The one from Germany may well work it has the 250mA output however it is only a maximum of 8W whereas your original is 11W, so long as you do not need more than 8W this is OK.
The constant 24V one would not be a good choice but may work, since if you look at your existing driver the minimum voltage is 23V (max 38V) and so if the lamps were fed 24V it is unlikely the current would be too much, however there would be no control of the current and if you wanted a 9W supply then the driver would be overloaded as it is only 6W.

Now I have actually looked the 250mA ones are not common, most start at 350mA.


Lamps that require constant current should have printed on them a wattage and current rating and not give a voltage rating.
If they need constant voltage then they will have a wattage and a voltage rating normally for individual lamps this is 12V, LED strips can be 12,24,36,48 V
Generally LEDs are wired in series for constant current and in parallel for constant voltage.

Mostly assemblies of LEDs might be constant current but individual items are constant voltage. It is much easier to get a 12V driver for LEDs and make sure it can take the total wattage which is what you would normally have for LED lamps on their own.
You have the slightly more complex arrangement of a set of lamps.
However usually they would be 350mA for which there are hundred of suitable drivers out there.

For your application I am assuming this is a set of MR11 LEDs in a unit or something like that, otherwise I would expect them to be 12V items even for MR11.

MR11 is not GU10
This is a diagram of some lamp bases for comparison.
View attachment 33868

I really do appreciate your time you take take to do these indepth explanations. so If i understand correctly in theory i could change a bulb to voltage constant one and then fit a voltage constant trannie as all of the leds have there own individual driver? All in theory off course.

 

[Richard Burns]

yes that would be fine.
The constant current driver is now a bit odd if they have individual drivers, most MR11 lamps on their own would be 12V, but do check the lamps just in case.
If the lamps say 12V on them then the wrong driver was used originally.

 

[assegayer]

So constant current drivers are only used for multilple leds?

 

[Richard Burns]

An LED lamp such as a GU10, MR16, MR 11 has multiple LED chips in it (in many cases) so presumably could be built to use a CC driver, however constant voltage drivers are cheaper to make so they design for those.

Where there may be a variable number of LEDs being installed such as in plinth light kits then a constant current driver is more flexible.

An LED as a component without any control circuitry would almost certainly benefit from a constant current source because once they start conducting the internal resistance is very low and so the current would just ramp up until they failed, the usual method of control is to apply a resistor before the LED so that the resistor limits the current drawn.

So in general single lamps are constant voltage, however multiple lamps can be either but often tend to be constant current.

 

[assegayer]

So if i am correct when each lamp is on there own driver its not too important whether cc or cv driver?

They could be wrong from the start, but are they really if each lamp has its own driver.

 

[Richard Burns]

You should use the type of driver specified for the lamp, whatever that is.

If you had a 5W LED lamp that required a constant current of 350mA you should be installing a 14.28V driver based on P/I = V. So fitting a 12V 5W driver would probably work OK but the lamp is not designed for it, however the current would very likely be stable as there is no variance between LEDs as there is only one LED.
Since it should need 350mA and you will probably supply less than 350mA with only 12V it may survive, however if there is no current control in the lamp then the lamp could fail.

 

[assegayer]

You should use the type of driver specified for the lamp, whatever that is.

If you had a 5W LED lamp that required a constant current of 350mA you should be installing a 14.28V driver based on P/I = V. So fitting a 12V 5W driver would probably work OK but the lamp is not designed for it, however the current would very likely be stable as there is no variance between LEDs as there is only one LED.
Since it should need 350mA and you will probably supply less than 350mA with only 12V it may survive, however if there is no current control in the lamp then the lamp could fail.

THANKS!! understand now