Hello Everyone

I'm a new member, i was just wondering as to how to go about replacing g4 halogen bulbs with white 10mm leds in my floor standing lamp. The leds are rated @ 3/3.1 vf, they are 11000-15000 mcd. The indoor floor lamp has 6 g4 bulbs which can be either 10w/20w per bulb. Would i have to connect any resistors up to each led etc? Any advice appreciated.

 

hi,
The g4 halogen bulbs are 12Vac 10Watt.

An LED is normally powered from a 'dc' source. They would require more than just series resistors in order to convert the floor lamp.
It could be done with extra electronic components.

How much electronics experience do you have.?

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Hello

Thanks for your reply, i'm just a novice so you could say a beginner. The indoor lamp comes with its own tranformer which is a NOVITRONIX MODEL NO 9815A & the other info printed on this tranformer is PRIM:230V/240 0.65A/50HZ/150W; SEK :12V EFF.
Hope this is of any info.

 

hi,
Whats the part number of the LED's ??
You have given the Vfwd, whats the continous rated current.?

Depending on the spec of the Led's it might be easier to replace the mains transformer with ac to dc mains plug adaptor.
Use the say 12Vdc from the adaptor to drive the LED's via suitable resistors.

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Eric
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From what i can gather it states:
Forward v--symbol vf-- min 3.0- max 3.3- unit v - test if= 20m/a

 

hi,
So assuming 3.2Vfwd at 20mA for the LED.

How many LED's do you want to use in the lamp.?

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

It may be easier to just buy commercial LED versions of those G4 bulbs.
There are various types available and some can also be used with AC.

eg:
http://www.ultraleds.co.uk/advanced_...bfa8e4&x=0&y=0

(I have no connection with that company)

 

I would be replacing all 6 g4 bulbs with 6 leds

 

Ideally i was thinking of getting the right value resistors & soldering one resistor per led & then after shortening the pins of the led & resistor simply push each led/resistor into the bulb holder. Is this possible or is it not as easy as it might be?

 

What's the output frequency of the transformer?

If it's a low frequency transformer then it'll be 50/60Hz, if it's an electronic tranformer then it'll be 20kHz to 200kHz.

Using a capacitor as a ballast and connecting the LEDs in reverse parallel might be a more sensible option than a resistor as it will dissipate less heat.

The only problem is the size and ripple current rating of the capacitor. For 50/60Hz you'll probably need a non-polarised electrolytic capacitor, for 20kHz to 200kHz you might be able to use ceramics but check the ripple ratings.

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A light bulb is 20W and produces a light output of about 3W all around. 17W is heat.
An LED produces a light output of only about 0.3W in a very narrow beam. 0.3W is heat.
You need 60 to 600 little LEDs to make as much light as the lightbulbs.
There are some very expensive 5W LEDs that produce almost as much light as a 20W halogen bulb in a wide angle.

The lamp won't be a lamp anymore with only 6 little LEDs. it will just be a dim flashlight shining a spot on the ceiling.

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Uncle $crooge

 

If from what you're saying that the leds wont be as bright as the g4's then i'm wasting my time, as that is what i was trying to achieve, as i do want the leds to light up the room to a reasonable level same as the g4's, but if they're not going to then i'll abandon this conversion.

 

What forward current are the LEDs rated for?

I'd use six 300mA emitters (I can provide a link to place which sells these if you like) on a good heat sink which should be equivalent to a 10W halogen.

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And http://www.silicontronics.com, same screen name as here.

 

Forward v--symbol vf-- min 3.0- max 3.3- unit v - test if= 20m/a
Basically i was looking @ the cheapest way to convert the existing lamp to run of leds without having to replace the transformer or buy expensive leds.
So if it can be done then great & if not then no great loss.

 

The keychain "flashlight" that costs $1.00 at The Dollar Store uses a 3.2V/20mA cheap little ordinary LED. Think how dim a floor lamp would be with 6 of them shining a dim narrow spot on the ceiling.

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