> Does an LED get brighter or dimmer with a slow change in voltage input?
> Dusty
Hello Dusty/Rusty/Brassy/etc.......
A slow change in voltage input is not going to get you the effect you are
seeking. Yes, the LED will change brightness to some extent, but not enough to
keep most of us happy.
It is, however, possible to purchase small electronic black boxes which will
cause LEDs to brighten and dim slowly and to a great extent. The effect of a
generator starting up on a steam loco can be simulated using LEDs if that is
what you seek. Some decoders have this effect already programmed into them.
These black boxes can be programmed to send small pulses of electricity to the
LED. The duration of the pulses is programmed into the black box and so a slow
rise or fall of brightness is possible using LEDs.
I have a unit which will be used to power the flashing red lights on a grade
crossing crossbucks. When the power comes on (triggered by an approaching
train), the circuitry starts to power up the LED. The LED light comes on quite
realistically (almost instantly, but not quite) like a bulb.
Similar black box products are used to power Mars lights, Pyle Gyra lights,
etc. where multiple LEDs are powered on or off in sequence to simulate the
figure 8 effects of a Mars light. Quite realistic to say the least.
Using a 5-LED design for a Mars light results in an effect not possible with
bulbs since even common mini-bulbs are too large to fit five of them into an HO
or N scale headlight lens. Not to mention the bulb heat melting the plastic MV
lens in the first place. Since LEDs can turn on or off instantly and bulbs
retain semi-uncontrollable residual light as the filaments cool down, the LEDs
are better suited to many special effect lighting situations.
In case anyone is interested, yes -- I am biased. Bring on the LEDs!
Cheers...Ed L.
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