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Quick LED question

D

davidlaska

Jan 1, 1970
0
James said:
I don't have a meter to check the brightness output, but it is more then
enough to replace the lamp in an lcd projector. I did a small board of 96
led's running on a 12 volt NiCad battery pack and took it outside at night,
just to see how it stood up to a flashlight. That small panel would light
the trees across the street from my house. The light it makes also seems to
make everything in high contrast. Give it a try and you will see what I mean
by that.

As far as wattage, (350 strings drawing .025 ma.) = 8.75 amp = (12v * 8.75
amp) = 105 watt on the panel. But you can judge the led brightness by that,
as Led's are more efficient then Incandescent lamps.

The angle on the led's were 20 degree if I remember correctly
I am not sure what a LCD projector is but there is a booklet on
building you own home entertainment theater where a LCD is projected to
the screen with a those outdoors Sodium light 400 watts ( last for ever
to).
 
L

Lord Garth

Jan 1, 1970
0
davidlaska said:
That was my mistake, I apologize.

Not at all necessary David...the jargon will come with experience.
 
J

Jason S

Jan 1, 1970
0
Jason S said:
I want to connect 8 white high brightness LED's together.
What is the safest way to connect them? I've thought about 1 resistor per
LED, but is it really necessary if all the LEDs have the same specs and
power requirements? I want to save as much room on my PCB as possible.

Power supply = 12V DC
LED type = White, 7000mcd, 3.5V Forward V, 30mA typical current.

If I connect them all in parallel, and use one single 3 or 5W resistor at
say, 39ohms, would that be ok?
Or would it be better if I just do two groups of 4 LEDs instead (with
separate 82ohm or so 3W/5W resistor for each group)?

The reason for the question is because as you know, the high brightness
LEDs are still quite expensive.

Thanks in advance,
Jason.

Wow, I didn't think a "quick question" would turn into a big discussion,
haha.
I guess everyone's got their own opinions about things, which I can
understand.

Regards,

Jason
 
D

davidlaska

Jan 1, 1970
0
James said:
I don't have a meter to check the brightness output, but it is more then
enough to replace the lamp in an lcd projector. I did a small board of 96
led's running on a 12 volt NiCad battery pack and took it outside at night,

there is a set of plans I going through for building you own home
theater. The lcd needed a light source and they were using a 400 watt
mercury bulb and ballest. You must have had those factory bulbs that
cost alot and burn out. and them switch to the led,s. It that very
good light for you?
 
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