Date: Mon, 22 Dec 2008 18:26:39 -0500
From: "Tim Lytle" <tjlytle-AT-gmail.com>
To: puptcrit-AT-puptcrit.org
Subject: Re: [Puptcrit] LEDs


On Mon, Dec 22, 2008 at 5:44 PM, Hobey Ford <hobeyone-AT-gmail.com> wrote:

> Can you dim LEDs?  I am messing with the toy theater and want to do
> some cool lighting, any suggestions?  Like those new high intensity
> LEDs.


First, I'm assuming these are just regular LED's, not some kind of LED bulb
(that replaces a normal light bulb), that would depend on the design of the
bulb. You'll be able to get some dimming using a simple variable resistor in
line with the LED (because you'll be limiting the current to the LED);
however, LED dimming is generally done using PWM (pulse width modulation),
which is essentially turns the LED on and off rapidly (but a constant
timing) and varies the amount of time in a cycle that the LED is in the 'on'
state. This would be somewhat analogous with the way a standard AC triac
based dimmer works.

Just did a quick google search:
Dimming with resistors: http://www.mikesflightdeck.com/led_dimmer.htm
Using PWM method:
http://www.lunaraccents.com/technology-LED-truck-lights-dimming.html

For PWM you can either use some standard simple electronics (timer ICs) or
go the microcontroller route (something like the Arduino, BasicStamp, etc).

Tim
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