[simpits-tech] LED Resistors

[simpits-tech@simpits.org]

Roy Coates wrote:
> 
> On Fri, 4 Apr 2003, Joseph Fagner wrote:
> 
> > Now, let's all have a group hug and we can talk about which resistors one
> > needs to power LED's.
> >
> 
> ok, now file this away in the "useful info" folder.
> 
> Generally, I personally now use 5v or 12v LED's which have the required
> resistor built-in. This makes for an easier and neater job. Anyway, here's
> the info you need.
> 
> To operate an LED from a given voltage a resistor needs to be placed in
> series with it. The correct resistor value in ohms is calculated using:
> 
>   R = (Vs - Vi) / If
> 
> Where:
> 
>   Vs is the supply voltage
>   Vi is the forward voltage drop across the LED
>   If is the forward current through the LED (in Amps)

Roy,
I'm a bit lost now. Powering an LED is easy, and I think I have an idea
of how to power an array of 9 LEDs, but now I have to also make the
array have the same resistance as a 12v/23w bulb. Any idea how to do
that? I'm working on a set of tail lights for my bike that will replace
the cats eye things with LEDs in the mesh vent things on either side of
the brake light (see http://home.swbell.net/lt1_z28/pics/s2_tail_1.jpg).
I'm about to whack the huge, useless fender off of there and when I do
that I'll lose the spot where the signals bolt. Besides, the LEDs will
be much sexier in those vents ;)
-- 
Steve
mysticz28@swbell.net
Jesus saves, Budda enlightens, Cthulhu thinks you'll make a nice
sandwich.