LED driver?

[Jim77]

Hi
I bought 4 X 5W Livarno LEDs GU5.3 12v from Lidl. Unfortunately they do not work as direct replacements for the fitted Halogens. They just light and extinguish immediately.

I have only tried one at a time. would fitting all four make any difference or do I need to replace power source?

I've read there are two types of driver - constant V and constant I - which is right for LEDs?

I'm guessing I need 12V - min 12W - constant current. Can someone please advise me?

Thank you
Jim

 

[Big Tone]

Hi Jim

Although not quite my speciality, (I'm from an electronics background), I don't see why it would be any different to the old small LEDs used in electronics.

So, in the case of in my field of work, from a table or spec, you look up the voltage drop, (across anode to cathode), and the specified current rating. It's just ohms law from there. E.g.

12v supply.
20mA current drain.
2v drop across diode.

The resistor value would be (12-2)/0.02= 500 ohms

Nearest preferred value = 470 ohms.

When you have several it's a matter of whether you have them in series or parallel. But it's just more ohms law. In short, it's the current you need to consider.

I feel the need for a disclaimer.

 

[Taylortwocities]

When they are in series, you need a constant current driver.
\In parallel you need a constant voltage driver

You existing lampos, I guess (hope) they are 12v and not 230V!!!

Otherwise you've cooked their goose.

IF they are 12v then the transformers may not work at such low current loads.

 

[PrenticeBoyofDerry]

It is likely you will need to swap out the transformers for LED drivers.
Are the lamps individually transformed or are they all supplied by the same trany?

 

[Lectrician]

Sounds like you need WIRE WOUND 12v standard lighting transformers, not electronic types. Electronic types cannot drive a load so small.

These replacement lamps usually have the driver circuit and current limiting built in, so just need a 12v AC supply.

What does the lamp say on it?

 

[ericmark]

Although a LED is current dependent when packaged this is all taken care of and they are voltage dependent as just needs a 12 volt feed does not really matter AC or DC the electronics within the package take care of this.

The problem is the switch mode power supply you have has both a minimum and maximum output and you have gone below the minimum I am sure if you leave one tungsten bulb in they will all work.

As already said a simple transformer would work OK but although it may say transformer on the box it is not really a simple transformer. Some of the new switch mode power supplies will go down to zero watts.

As to cure not sure what is best swapping power supply or moving to low voltage rather than extra low voltage. The whole idea of the low voltage was quartz lamps have to run at a very well controlled temperature two high and life reduced and too low and life reduced the power supply removed small voltage variations and extended bulb life. But with LED not a problem so unless in a bathroom or other place where we want extra low voltage for safety there is no real gain with extra low voltage using LED lamps.

 

[Jim77]

Thanks for your reply.

Yes, the originals are 12v. Must be in parallel as one has been out and other 3 still light.

I just tried all 4 in place and one stays lit the others come on then instantly off - not blown as I can repeat this.

If I replace the existing transformer with this it should work do you you think?

Jim

 

[Taylortwocities]

So, do you have one transformer that serves all of the lamps, or is there one transformer for easch lamp?

Your approach, the complexity of rewiring and the cost will all depend on this.

 

[Lectrician]

Do you have one transformer or one per light as it currently stands?

If you have 4 seperate ones, then one is obviously happy, but the other three not. Alter the wiring so the happy one feeds all four.

If you have just one transformer, swapping it for a wirewound type is all that should be required.

These lights are designed to run from older ELV lighting transformers, not via LED drivers. What do the lamps say on them in terms of the supply?

http://www.tlc-direct.co.uk/Products/TLT50slash1.html

 

[Jim77]

OK not sure on number of transformers - going into loft shortly to check.

Markings on lamps are: 12V ~ 50Hz - 5W, 3000k, 620mA
IAN 01149 - model no Z31540A

I'll let you know what I find.

Thanks
Jim

 

[Lectrician]

So they require a 12V AC supply (50hz frequency), and will draw 620mA.

A torroidal transformer will deliver this. An electronic transformer wont.

 

[Taylortwocities]

Surely 4 x 620mA ?

 

[Lectrician]

Surely 4 x 620mA ?

I was talking each lamp, in reference to my "what does it say on the lamps?"