Re: Help Getting Started - Simple DC Circuit

If you need that much quantity, don't go to RadioShack. Check out
www.mouser.com - they are WAY cheaper and have no minimum.


"Mark Jerde" <MarkJerde@xxxxxxxxxxxxxxxx> wrote in message
news:Y%adf.1862$rO4.1388@xxxxxxxxxxx
> Randy & David -- Thanks for the replies.
>
> > 2 'C' cells in series should give you enough power
> > for short periods, and 3 volts will be sufficient
> > to light the LEDs. You could try 2 'AA' cells, but
> > I'm guessing they won't handle 30x0.02A = .6A for
> > very long (if at all).
> >
> > Each LED&switch will need a separate resistor.
> > Don't try to parallel them thru 1 resistor; you'll
> > let the magic smoke out of the LED's. :(
> >
> > To calculate the resistor values:
> >
> > R = (Vcc - Vled) / Iled
> >
> > where Vcc is the supply voltage, Vled is the
> > forward voltage drop of the LED, and Iled is the
> > operating current of the LED.
> >
> > You can find a minimum R value for your LED's,
> > and try larger values that still give acceptable
> > brightness with less power consumption.
> >
> > HTH
>
> I'm just back from Radio Shack with a package of these to get started
> thinking:
>
> http://www.radioshack.com/product/index.jsp?productId=2062588&cp
> 20 assorted LEDs, 2 - 3V, 10-20 mA
>
> (They were the only thing economical. Other LEDs were one or two per
> package, $1.98 to $4.98. I'll get another package when I go to get the
> battery holder & resistors.)
>
> Am I reading the specs right to use Vcc = 3 V, Vled = 2.5 V and Iled = 15
> mA?
> R = (3 - 2.5) / 0.015
> = 33.33 Ohms
>
> When I did electronics many years ago most of the resistors were in the
> kiloohm and megaohm range. 33 ohms seems wrong. Am I missing something?
>
> Thanks again!
>
> -- Mark
>
>


.

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