Another mr 16 led transformer question

[ban-all-sheds]

As the OP has more than one, there is another easy way to find out.....

Back to back???

 

[aveatry]

Well all bulbs fitted and so far so good no problems, I left them on for about 3 hours to check.
Wow ! they are bright and love the cool white colour I could of got away with 4w ones but screwfix didn't do them and to get bulbs online somewhere would of been a week turnaround at best if I had to send back, whereas screwfix is down the road here is some before and after pictures.
View media item 96941View media item 96939

 

[Mikefromlondon]

Brilliant, Not bad at all, took you just under an hour! now I have been looking one of these LED lights, and found some amusing results, as I was trying to find out why they start flickering after about 5 minutes, using electronic transformer, and here is what I found:

first the characteristics, if you apply straight 12 DC from a bench power supply they draw 420mA , hence why they are called 5Watt, as 12 x.42 =5W

Now strange things start happening when you lower the voltage, ( well not quite strange for me as I can explain) these LED Lights clearly state not dimmable, so lowering voltage does not reduce brightness as one would expected in simple LED circuits with a current limit resistor.

So these particular LED lights seem to use a switched mode built in power supply to further regulate the current and voltage required to drive these LED lamps.

As the input voltage goes down, the internal circuit compensate for a lower supply voltage and starts to draw more current to maintain a constant power (product of voltage and current) so the light intensity remains very constant.

LEDs with a simple resistor will dim LEDs as the voltage is varied, since the current through the resistor is proportional to voltage across it. So these constant Power LEDs have built in circuit and one can hear it uses a switched mode operation as its interaction can be heard on a MW radio and the intermediate signal between the radio receiver and the LED light can be heard to vary in pitch as you turn the voltage up or down, I tried to go all the way up to 16Volts and it was drawing just over 300mA and did not fancy taking it any higher, and the Light remained very constant so from about 6volts to all the way to about 16v the light intensity did not change.

So these Enlite LED lights have a complex circuit inside to compensate for voltage drop, and that is the reason why electronic transformers are not suitable as the two switched mode power supply circuits can clash with one another, their switching frequencies can interfere with each other and thus start to flicker.

And you can see why they flicker for a while and then go steady as the two chopping circuits one in the LED lamp and the other in the electronic transformer starts to interact with one another, as the two switching frequencies phase in and phase out, so the flickering comes and goes in waves.

16.00v - 310mA (Absolute maximum voltage before expected destruction)
12.00v - 420mA
11.50v - 440mA
11.00v - 460mA
10.50v - 480mA
10.00v - 510mA
09.50v - 540mA
09.00v - 580mA
08.50v - 620mA
08.00v - 670mA
07.50v - 720mA
07.00v - 800mA
06.50v - 870mA
06.00v - 1000mA (1 Amp)
05.50v - 1160mA
05.30v Starts flickering and then any further reduction in voltage goes out completely

The bulb tested was MR16 brand name ENLITE, with 4000K colour temperature (bright white) 60 degrees spread and cost £4.90 each.

More technical data on this site;
http://www.ukelectricalsupplies.com...qxyrhkx8ozquAg04PVzHpyWCteH5ed-ngQaAoN48P8HAQ

 

[aveatry]

Interesting - not that I fully understand, but I get the gist of it, I wonder what tec the screwfix LAP ones I just fitted have inside as mainly the reviews did not complain about flicker.
But I found this review, which sounds exactly like what your bench testing has found
Flicker issues 3 Aug 2015 By DaddyT, Swansea

" Bought three packs of these following the good reviews and the competitive price. They were to replace all the lamps in our kitchen and dining room which use crazy amounts of electricity. Unfortunately, having replaced the 10 in the kitchen we have a major issue. The lamps flicker and strobe to such an extent that they cause people to have headaches. The strange thing is they don't do it all the time or at any particular point. Some times they all flicker on start up, some times when they have been on a while. Other times only one will flicker other times all of them will flicker. It is a very annoying feature when it happens though and hurts your eyes. I will now put the original lamps back in. "

Its a shame that it is not widely known about transformer issues with mr16 LEDS

 

[bernardgreen]

Provided it is a DC 12 volt supply then the flickering might be cured by a large smoothing capacitor on the 12 volt output of the switch mode power supply (SMPS ) along with some smaller high frequency capacitors. Large electrolytics can have a significant impedance at high frequency due to the inductance of the electrodes being wound together hence the need for other capacitor(s) to smooth out high fequency ripple which would ( could ) affect the switch mode driver n the lamp.

The problem with this is that the large capacitive load on the SMPS might delay or prevent the SMPS from starting up and / or then stabilising its output voltage.

 

[Mikefromlondon]

Given the time, I haven't tried but an Inductor capable of carrying 1 to 2 amps and of a few mili henries could be tried in series to stop High frequency (HF) noise as well as a HF bypass capacitor as suggested above to remove any noise transmitting back or forth into the main switch mode electronic transformer and visa versa to remove interaction, this may stop flickering, given the fact power wound transformers are not only bulky but also expensive compared to these switched mode power supplies. (SMPS)

Edit: During our replacing the halogens with LED bulbs, when the flickering started, I monitored the voltage from the new SMPS, it was all over the place, giving me very unusual voltage readings from 3.5volts to around 9 volts, whereas it should have been maintained around 12v. So this clearly indicated the SMPS were shutting down due to interaction, a kind of vicious circle, where if the LED were getting lower voltage, they start drawing more current, and when they start drawing more current the SMPS is already restricting its output voltage possibly due to momentarily overloading, and in turn the LED demand even more current so the SMPS goes even further down hence the lights flicker as the SMPS tries to recover from a complete shut down to almost full output again, so a whole lot of vicious cycle starts and results in severe flickering. At first it starts normal, then some lamps starts to flicker, then almost all start to flicker, and finally the flickering continues constantly, starting with ripples first.


I do like these LED bulbs, the4y are the way forward to save this planet, and our pockets against expensive electricity bills, I could for example cut my workshop lighting bill by a lot, My workshop used to have 8 x 5foot long tube lights each drawing 55watts, so that meant i was using almost half a kilo watt of energy just for lighting and eventually i got used to running just 4 instead of 8, cutting my electricity bill down, and now I could replace each tube light with say 4 LED bulbs and thus bring the consumption further back to 20watts from 55watts per tube, so total reduced from 220watts to just 80 watts, and i could also do the same for my house dining room which has no natural light and uses 3 x 14watts (42 watts of energy saving lamps) the light output of these lamps is equals to conventional filament lamps of 3 x 60watts candle lights, LEDs could bring the 42watts down to about 30 watts if I can use 6 x 5watt led bulbs.

 

[aveatry]

Due to the success I have had here I now have a new one for you all to argue -DEBATE !
//www.diynot.com/diy/threads/my-new-whats-my-transformer-qiuz.451508/