Re: Help Getting Started - Simple DC Circuit

On Sat, 12 Nov 2005 00:51:04 GMT, "Mark Jerde"
<MarkJerde@xxxxxxxxxxxxxxxx> wrote:


>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?

Red, yellow and green LEDs are around 2 volts, and I find they are
quite bright enough with 10 mA, so, with 3 volts, you could use 100
ohms.

Blue and white LEDs want about 3.6 volts, I believe, so you'd need
another cell or two for them.

Resistors under 1K are certainly not uncommon - I think I've got a few
values under 10 ohms in my stock at work (although I'll admit that I
don't use such low values very often.)




--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca
.

Relevant Pages

  • Re: LED question for electronics wizards
    ... Then, I might try two 500 ohm resistors in series, and if really brave two ... LEDs have a brightness range and a current range. ... I'll do the math and see what the optimum voltage source is for 25 mA and 500 ohms. ...
    (rec.models.rc.air)
  • Re: PC port question
    ... have 330 ohms? ... You could try the original schematic with 1k resistors ... The LEDs wont be as bright, ...
    (sci.electronics.basics)
  • Re: Help Getting Started - Simple DC Circuit
    ... Other LEDs were one or two per ... I'll get another package when I go to get the ... count on using 'assorted' values for the resistors. ... Try finding a set of resistors from 47 ohm to maybe ...
    (sci.electronics.basics)
  • Re: led questions
    ... i have a BASIC understanding of electronics and ... but not leds. ... > resistors in parallel, but noone really goes into why. ... I used 220 ohms for my six volt motorbike. ...
    (sci.electronics.basics)
  • Re: Help Getting Started - Simple DC Circuit
    ... >> Each LED&switch will need a separate resistor. ... Other LEDs were one or two per ... > package, $1.98 to $4.98. ... 33 ohms seems wrong. ...
    (sci.electronics.basics)