need help. Lost about LED's

[luckless wolf]

good evening everybody!

I got problem about myheadlight LED's
I got this result on my project :(
using 5mm 40000mcd giga bright led (3500kwarm white)
http://img11.hostingpics.net/pics/8653281414936102018620310641312078686019n.jpg (http://www.hostingpics.net/viewer.php?id=865328141493610201862031064131207868 6019n.jpg)

and I'd like the square be fully lighted like reals
http://img11.hostingpics.net/pics/170438i178501.jpg (http://www.hostingpics.net/viewer.php?id=170438i178501.jpg)

thanks a lot for helping me :D

[ricm]

what's the power source for the LED? direct from battery, or MFU, or something else?

Is it wired up with anything else in the supply circuit? do you have multiple LEDs wired together in the same loop?

Also, do you have any current (amps) and voltage ratings for the LED? You might also find a spec for the angle of the LED 'light cone', also known as the 'viewing angle'. Many LEDs have quite a narrow cone, eg. 30 degrees, which means the light shines from the LED at up to 15 degree angle from each side of 'straight ahead'. The impact is that for LEDs with a narrow light cone, they only look at their brightest when viewed head-on. In such cases, because they do not disperse light very well to the sides, you may not achieve the effect of a fully filled reflector like you want. But a correctly wired LED should be bright enough to achieve something very close to it by the time the light has refracted through the clear lens...and having said that, your LED does look really dim in the photo.

Photos of the setup and info on power supply/ LED specs might help solve the problem....

[luckless wolf]

what's the power source for the LED? direct from battery, or MFU, or something else?

Is it wired up with anything else in the supply circuit? do you have multiple LEDs wired together in the same loop?

Also, do you have any current (amps) and voltage ratings for the LED? You might also find a spec for the angle of the LED 'light cone', also known as the 'viewing angle'. Many LEDs have quite a narrow cone, eg. 30 degrees, which means the light shines from the LED at up to 15 degree angle from each side of 'straight ahead'. The impact is that for LEDs with a narrow light cone, they only look at their brightest when viewed head-on. In such cases, because they do not disperse light very well to the sides, you may not achieve the effect of a fully filled reflector like you want. But a correctly wired LED should be bright enough to achieve something very close to it by the time the light has refracted through the clear lens...and having said that, your LED does look really dim in the photo.

Photos of the setup and info on power supply/ LED specs might help solve the problem....

I tried on a hobbyking led kit, then a modified servo
about the pic I wired the LED with two 1.5Volt batteries
but about you talk about this I'll try with diffused light LED for the angle
there are the LED specs
http://img15.hostingpics.net/pics/381433fichetechled.png (http://www.hostingpics.net/viewer.php?id=381433fichetechled.png)

[ricm]

LED brightness drops off quickly once you get below the typical rated voltage, then it won't work when you get to the minimum. So your 3V supply for 1 LED rated for 3.1V isn't enough, which is why it looks dim. You need to give enough voltage to be somewhere between the typical rated voltage and the maximum. I would suggest taking power from the main battery pack (7.2V?) with a Y-lead, then have 2 of these LEDs in series (for left and right side) with a 20 ohm resistor. This will give each LED a voltage of around 3.3V - 3.4V which is between the typical and max ratings, should give you maximum brightness. For only a couple of LEDs this won't have any meaningful affect on battery life.

You can see the 50% power angle is quite narrow (15 degrees), so once you get to 15 degrees angle away from 'straight ahead', you lose half of the LED brightness - effectively making the 'light cone' 30 degrees. So its important to make sure the LED has good power supply to help give you the best chance of 'filling' the square reflector like you want.