LED Replacement G4 Bulbs

[RJH]

I'm thinking of replacing 3 12V 20W ceiling fitted G4 halogen bulbs with these:

Is there any way I can tell if the existing transformer is suitable?

Thanks, Rob

[Andrew Gabriel]

Most unlikely for two reasons:

The lamp is specified for DC. Your existing transformer is almost certainly AC.

It will say on it if it has a minimum load. A common rating for an electronic transformer will be 20-60W. Electronic transformers are unlikely to be able to support a drop from 20W to 1.5W.

[RJH]

Thanks very much!

Rob

[Terry Fields]

These lamps are only 100 lumens as against a halogen G4 at about 200. They will be somewhat dim in comparison, especially in 'warm'.

[RJH]

will be somewhat dim in

Yes, I'd gather, it's a stab at background lighting in a windowless basement room using existing fittings. Quite new to all of this . . .

Rob

[Geoff Pearson]

9 quid each!

[dennis]

will be somewhat dim in

I have just replaced four 12v 20W halogen reflector lamps with four lidl LEDS for £10 that are 1.4W and they are more than half the brightness. They also quote 100 lm so I doubt if the halogens actually give out 200 lm.

I did replace them last year with some 3W LEDs but they failed within a month, probably due to them being spots and being unable to get rid of the heat. These are floods and have seven surface mount LEDs and give a nice even light. There is no heat build up and they aren't even warm.

[Brian Gaff]

Might it not have a bridge rectifier built in though?

Brian

[DerbyBorn]

"Brian Gaff" wrote in news:kgikbo$f9r$1@dont- email.me:

I saw one of these 4.5 watt LEDs today. Very impressive!

[Andrew Gabriel]

Bog standard 12V "electronic" transformers don't. It would serve no useful purpose, and waste power due to the forward voltage drop of the diodes, and their switching times given these run in the 20-50kHz region where power diode switching time starts to become a significant issue (always an issue in DC switched mode PSUs).

The output is directly from the secondary winding around the ferrite core, with no other circuitry on the output side.

Some LED lamps include a bridge rectifier, but this one does explicitly say it runs on 12V DC, which strongly suggests it doesn't. I would hope that it does at least include a protection diode, as the sockets are not polarised.

[Windmill]

Do any of these LED lamps incorporate back-to-back LEDs ? That eliminates the need for protection diodes.