my new whats my transformer qiuz

[aveatry]

due to the fantastic knowelagable i got on here yesterday about a transformer and leds I now have another transformer that I want to change its bulbs for leds.
The transformer is in the attic and so can be got to if ultimately I need to change it, it is running 3x20w G4 capsule bulbs that I want to swap for LED 2.5w.
It isnt as heavey as my other WW one but does not have a stated min watt like a WW one.But it does say electronic.
So here it is what do you think will it be ok running 7.5Ws of led.
View media item 96940

 

[winston1]

It is a switch mode power supply. It may or may not run LEds, you can but try.

 

[Mikefromlondon]

Sorry long post, but much rather explain clearly what happened when I tried changing 12v halogens to 12v LED lights for a mate.

When I did my mate's change over to LED lights, it wasn't a question of swapping them over, because with his old SMPS (electronic transformers) that ran his 20W halogen bulbs quite happily, and he had one per halogen light, so in all he had 8 such SMPS and one for each Halogen.

So when he swapped halogen with LED, it started to flicker, that is when I came into the scene, as he called me over to find out why they are doing it, at first I had no idea as I was not into LED lighting, so I advised him to go back to the shop where he bought them from and and ask them why those LED lights won't run smooth on his old SMPS.

The shop man told him that he could sell him two Powertran brand SMPS and it could run 4 LEd lights easily as it is rated at 20-60 VA.
Strangely I did not notice until now, that this Powertran SMPS is Dimmable apparently, says on it, but doesn't have a separate control input for dimming as I saw on one other thread on here that some dimmable ones require 0-10v for dimming.

This one has no control input for dimming, so I am assuming it would dim on normal tungsten bulb type dimmers using SCRs.

Any way, I removed all his old SMPS, first from one row of 4 lights, and reconnected his wiring in parallel and where the mains 230v came in I wired the new SMPS, and connected its output to all 4 lamp holders, and then as we went about plugging one LED bulb at a time, there was no flickering at first, so by the time we had plugged 3 LED lights in, we could not plug the 4th one in because we had mislaid it and could not find it, so we left 3 connected and running with no flicker,

Next day I went back in and my mate got 4 more for the second row, and I went about doing the same to the second row what I did to the first row, removed his old SMPS, and discarded them, and rearranged wiring in parallel to run on another new single Powertran SMPS.

He also bought an extra LED bulb as we had mislaid one, so as we finished rewiring the second row, and inserted all new 4 LED lights in second row, and when we turned power on, they started to flicker, all 4 flickering in row 2, and then we switched on row 1 that had 3 LED bulbs, and it ran fine, no flickering, then we added the 4th bulb in row 1 and switched all 4 new LEDs in row 1 and they started to flicker as well, and quite badly so, then we removed the 4th LED bulb we added, so leaving 3 in Row 1, and now they were still flickering, something strange was going on and we could not explain logically,

this is when I started to check for 12v on ROW 1, and the voltage was all over fluctuating between 3.6v to 11v something, and the same thing was happening in row two, all 8 LEDs On and bad flickering, One LED even started to flicker like a disco light flashing ON and OFF.

This is when I suggested to my mate that I think we need proper wire wound transformer, and then he said wait I might have a couple, this is when he brought two black potted transformer same as OP's and weighed really heavy so there was no question it was a wire wound transformer but nicely build and all potted into a plastic housing with two set of terminals at either end, primary and secondary clearly marked as 240V and 12v

I swapped these and all went brilliant and stable.

Your SMPS Transformer cannot be said to not work, I would try it first before deciding to take the WW route, if iot works on your LEDs then you don't have to buy expensive and heavy wire wound.

and remember my mate's LED bulbs have a compensating circuit build into them that will provide a steady light at a wide variation of input voltage, but if the SMPS cannot meet the required current demand by 4 LED bulbs then it will start going into a vicious flickering cycle.

All I can say is let us hope these electronic SMPS can run many other brands of 12v LED bulbs, otherwise you are better off not buying 12v LEDs but go for 230V LED bulbs and do away altogether with SMPS.

 

[aveatry]

I think that I am also starting to realize that I may need a dc output as that one is ac.
Its to run G4 bulbs that I have on order, some suppliers say they are ac or dc - can run on both and others say dc only.
If I put a dc bulb in a ac supply what will happen

 

[aveatry]

I think your mate needs one of these dedicated LED drivers, as will I for my 3 x 2.5w G4s I think
https://www.ledhut.co.uk/drivers-fittings-switches/drivers-transformers.html

Some useful info on the subject here http://www.ledconnection.co.uk/blog/category/leds-and-issues-with-transformers/

 

[JohnW2]

If I put a dc bulb in a ac supply what will happen

If it is a non-polarised DC LED (ie.e. without an indication of which side must be connected to negative and which to positive, then it should be fine (would have to contain a bridge rectifier, or equivalent so as to provide the LED element with the correct DC polarity, regardless of supply polarity. On the other hand, if (unusually) the LED lamp is 'polarised', then anything is theoretically possible (including killing the LED), depending on exactly what goes on within the lamp.

Kind Regards, John

 

[Mikefromlondon]

i think manufacturers realised that for consumers to replace LED bulbs if they were polarised, then half of them may be returned as not working, that is because people may have plugged them wrong way around if they were polarised, so it is not a big thing to insert a bridge rectifier to convert ac into DC so all manufacturers would have incorporated this in their design approach, diodes to form a bridge rectifier cost less than peanuts.

So I will be highly surprised if you came across any LED bulb that was polarised with + & - polarity signal, and inserting an LED into a DC or AC would be no different as build in bridge rectifier would take care of polarity issues. You need not worry. You must not place an Electrolytic smoothing capacitor across an AC voltage as the capacitor would heat up and blow like a fire cracker or they now incorporate a small vent to prevent blow up, long time ago we used to deliberately blow capacitors and obtain tons of fun in our workshop when the boss was out dining while he left us in charge.

 

[aveatry]

This is what I have on the way to me tomorrow https://www.ledhut.co.uk/spot-lights/g4-led-bulbs/2-5-watt-g4-led-bulb.html
Looking at the bulb at least in the picture it has DC 12v printed on it, but when I search for others that look identical they seem to have dc on one side and ac on the other or I have seen printed on another one ac/d (something like that )which I assume is ac and dc compatible.
There is no info on the site about the detailed spec so I may just have to wait and see what comes and what is written on the box

 

[winston1]

Some useful info on the subject here http://www.ledconnection.co.uk/blog/category/leds-and-issues-with-transformers/

What a load of badly written tripe.

e.g.The older style magnetic transformers are quite simple and use good old fashioned copper wires to provide the necessary resistance to provide a 12 volt output. The electronic transformers, however, use a complex mixture of electronic circuits and witchcraft to provide the 12 volt output.

er, NO the change of voltage is not done by resistance. There is no witchcraft involved, just pure electronics.

e.g. The incoming mains voltage is normally always 230v AC (alternating current) and the transformers will normally change this voltage to 12v DC (direct current).

Transformers don't change AC to DC, that's what rectifiers do. Anyway lighting transformers or SMPS normally give out AC.

e.g. If you’re lucky, they’ve been created to accept both AC and DC incoming voltage and you won’t have to worry about the voltage supply,

Really, so that presumably means you can connect them straight to 240v AC.

 

[Mikefromlondon]

well good luck in your endeavor, how it all goes please let us know, and if you are pleased with your version of the bulbs, as these are very wide angle light dispersion.

I tried one similar to this in a bayonet cap, directly driven by 3Watt 230v in a candle shape, for my bathroom, it was casting very sharp shadows, so i then bought another one with a diffused glass cover, this one gives slightly less lumens but casts less sharp shadows. For my cloakroom the 3watt one is perfect as for lumens, i had a 11watt energy saving one before. and before that i used to use 60watt ! that was madness! but then again, LED lights are relatively new and will take over our Earth!
Poor Eddison, his bulbs are now under a pile of rubbish in landfill! But never mind if he hadn't invented the light bulb, no LEDs would have been possible!

 

[aveatry]

Some useful info on the subject here http://www.ledconnection.co.uk/blog/category/leds-and-issues-with-transformers/

What a load of badly written tripe.

e.g.The older style magnetic transformers are quite simple and use good old fashioned copper wires to provide the necessary resistance to provide a 12 volt output. The electronic transformers, however, use a complex mixture of electronic circuits and witchcraft to provide the 12 volt output.

Made sense to me - remember that they are trying to explain it to your mother-in -law (and me)

 

[aveatry]

well good luck in your endeavor, how it all goes please let us know, and if you are pleased with your version of the bulbs, as these are very wide angle light dispersion.

I tried one similar to this in a bayonet cap, directly driven by 3Watt 230v in a candle shape, for my bathroom, it was casting very sharp shadows, so i then bought another one with a diffused glass cover, this one gives slightly less lumens but casts less sharp shadows. For my cloakroom the 3watt one is perfect as for lumens, i had a 11watt energy saving one before. and before that i used to use 60watt ! that was madness! but then again, LED lights are relatively new and will take over our Earth!

The 3 that I am on to now are in front of a set of mirror wardrobes on a separate switch to give some extra light when looking in them or looking at yourself in the mirror.
On a seperate note
What I have found with gu10 led down lights is that you need more in a room but possibly keep them at a lower W - so little and often to get a nice even light 4 or 5w = 300 ish lumens you may need to experiment.
You know those in my kitchen I am now thinking that they are too bright (never thought I would be saying that about leds ) they have finally come of age.

In my bathroom that is 3mx2m I have 5 at 5W (340 lm ) and to keep ip65 I have downlights that the bulb sits behind a sealed frosted glass which does a very good job at softening and spreading the light, 4000k or 6000k is perfect

 

[ericmark]

A switched mode power supply or pulse width modulated is actually doing what the name suggests it is controlling the energy delivered by switch on and off.

the on bit is called the mark and off bit is called the space and it alters the ratio between the two in order to regulate the power supplied. However the mark (on bit) can never be zero and there are limits to switching speed so a simple device can't run from zero to max output.

However more complex units can get around the problem, but this is not required to run a quartz halogen lamp. With a DC output it is easy to smooth so you have a spot on output but with AC that's not so easy, and is not required with quartz halogen lamps, all one needs to do is work at a high enough frequency so you will see no flicker in the lamp and the lamp will no over heat on the pulses. Higher frequencies also mean you can use very small transformers so running in the Mhz range is common. The down side is the length of cable between the unit and the lamp needs to be short as it can transmit at those frequencies.

Using these cheap units to power an LED means you likely lose the damping effects of the quartz halogen and also you are putting a diode in the AC circuit which can easy then start transmitting the power rather than using it local and much depends on the circuit inside the lamp as to how it will react to high frequency AC specially as it is rather a dirty output in the first place.

It could internally in the lamp rectify and smooth the supply and feed it to a second PWM device to feed the LED with a constant current exactly matched to the LED, it could also be feeding the LED's with spikes very close if not exceeding the avalanche break down point of the diode and as a result damage them and reduce the life expectancy of the device. We simply have no idea what will happen it could even be jamming the local emergency services radios although very unlikely.

Even using a 50 Hz transformer may over stress the LED's where they get 17 volt peaks instead of the 12 volt they are designed for but likely the manufacturers will allow for 12 volt sine RMS 50 Hz supply so likely a simple transformer will work. But with 12 volt square wave RMS at 5 MHz it is just guess work we have no idea what it will do or even if rectifying the output will upset the power supply.

The cure is easy dump the electronic transformers and use 230 vac lamps then no chance of a miss match. The other is to use a smoothed 12 volt DC supply. Although an AC supply may work, the question is for how long? With a 25,000 hour life that's at 4 hours a night average that's around 17 years so until fitted for 5 years you really don't know if your reducing the units life or not. An if it fails after 3 years you have no way to prove if used 24/7 and so at end of life or if just used for 4 hours a night average so no chance of getting money back even if you have not damaged them by using on a switch mode supply. I used 4 x 0.58W GU5.3 LED MR16 lamps in my bathroom and they lasted just 6 months, at £1 each I was not really worried about short life but am loathed to pay out for 12 volt LED lamps at £5 each if the life is going to be that short.

 

[333rocky333]

mike from london
why did your mate initially buy 2 new electronic trans if he already had 8 that he was removing


Afaik, if you buy megaman 12 volt lamps, theres a page on ther website listing tried and tested compatible transformers and dimmers

 

[Mikefromlondon]

My mate done a new kitchen, replaced everything new, except lighting, so he next tackled lighting on his own, he replaced his 12v halogen with a 12v LED and found it was flickering badly, so he went back to the shop (local electrical distributor) he advised him to try a newer SMPS, and said they were only a fiver each, and he advised my mate that he could wire up to 4 LED bulbs on one single SMPS easily, so for two banks of 4 lights my mate bought 2 new SMPS.

Ironically he sold him Powertran brand SMPS, which clearly says they are meant for halogen 12v lights!!!

But now he was no good at swapping SMPS, so asked me to do the older SMPS to newer ones, that is when I got involved. Prior to this I had not carried out any LED lights swapping and so had no previous experience, but now I have and can advise accordingly. BTW, the local distributor probably did not stock other brands, but the Enlight brand. each to their own really.

So you could say the electrical distributor should have known better, I am sure he must have sold hundreds of LED lights and customers must have come back and told him that LED lights require special SMPS or wire wound transformers for smoother running.