Are LED's good for backlighting a display?

[homer09]

I want to illuminate my aluminium knob for my gainclone chasis. Basically, it is a 2" (5cm) diameter knob. A 2 and 1/8" (5.3cm) hole will be cut into the face plate. I want the space between the knob and the faceplate to glow.

What i've seen done in commercial amps/tuners when they want to illuminate a dial or display is they usually build a white, light-sealed background behind the display, then cover the display with a see through plastic and in the space between the white backdrop and plastic face, an incandecent lamp is inserted out of sight. This has the effect of making the white backdrop glow. For colour, a plastic coloured transparency is placed infront of the white bulb.

But, i think incandecents are too gready with current. I want to limit the current draw wasted on esthetics. LEDs draw less current so my question is:

What type of LED is good for this kind of back lighting over a relatively large area? Im looking for brightness and uniformity as well as low current draw.

Im also opened to other ways of lighting the space around the knob. thanks for any suggestions

[thomas997]

Your going to either need a lot of LEDs, or a way to spread out the light.

To spread out the light you use a clear plastic, and drill out a hole in the middle to fit the knob. Then have a point where the LEDs light can enter. # of LEDs would depend on the size of the circle, and how even you want the light (in my ex. its 2 and fairly uneven, 4 would be better).

No idea what LED type would be the best.. but I would just get the cheap ones on ebay. As for colour, blue or red are very bright for low cost (and imo look the best).

I kinda suck at describing it so here are some example pics (notice the red on the right, blending colours looks cool, but brightness may be uneven).

[thomas997]

back

[johnf]

You can buy LEDs with a light pattern suitable for backlighting. Vishay/Telefunken makes some.

[cpemma]

One way is to use neon string, lots of shapeable light but the inverter drivers sometimes buzz a little. For another effect, using those nice aluminium knobs with a marker slit, and build the led into the knob.

[homer09]

Thanks for the ideas guys

I see there are LEDs called superbright LEDs. They have an mcd in the thousands vs in the 50's. Anyone have any experience with these type of LEDs and are they really much brighter?

[johnf]

I use them and, yes, they are really bright.

You may find it hard, if you use just a few, to produce an even light distribution around your knob without bright spots. Maybe, you shouldn't try. Perhaps you could use a bunch of inexpensive LEDs to produce diffuse, graduation bright spots around the dial.

[homer09]

Hey John,

What do you think of this setup (attached pic)? Do you think this would work? What brightness LED should i use for a 2" diameter knob?

Thanks for the advice.

[cpemma]

Originally posted by homer09
I see there are LEDs called superbright LEDs. They have an mcd in the thousands vs in the 50's. Anyone have any experience with these type of LEDs and are they really much brighter?

They're certainly brighter, but due to the way candelas are scaled, not hundreds of times brighter (any more than a 100W amp is 100x louder than a 1W). Most important in your application may be a wide viewing angle, which cuts down the cd rating but may give more uniform light.

[TwoSpoons]

Superbrights are really only bright because they emit most of their power over a narrow angle.

In your diagram you might want to use 'opal' white acrylic instead of clear.