Discuss Led downlighters flickering in the Electrical Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

Reaction score
34
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?

Led downlighters flickering 20161009_165914 - EletriciansForums.net
 

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
 
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.
 
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?
 
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.
 
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
 
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.
 
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?
 
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??!
 
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?
 
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?
 
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.
 
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.
 
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
 

Reply to Led downlighters flickering in the Electrical Forum area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock