Subject:
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Re: Homemade LED Bricks
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 12 Nov 1999 12:13:50 GMT
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Original-From:
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Russell Nelson <nelson@crynwr.com!AvoidSpam!>
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Viewed:
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999 times
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Keith Miller writes:
> basicly.. it's i*r=v where i = current in amps and r = resistance in ohms
> and v = voltage in volts..
> so..
> If we want to find out the resistor's value.. we re arrange it like so..
> r = v/i
> so 10 millamps (typical led current) = .01 Amps..
> And at 9 volts it becomes
>
> r = .01/9
> r = 900 ohms
Yeah, but it's not 9 volts. It's 9 volts minus the .7 volt drop
across the LED. Plus some of the new eyeburner LEDs take as much as
40ma, so you have to know how much current the LED takes. Give it too
much and you greatly shorted its life.
--
-russ nelson <sig@russnelson.com> http://russnelson.com
Crynwr sells support for free software | PGPok | Government schools are so
521 Pleasant Valley Rd. | +1 315 268 1925 voice | bad that any rank amateur
Potsdam, NY 13676-3213 | +1 315 268 9201 FAX | can outdo them. Homeschool!
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Message has 1 Reply:
 | | Re: Homemade LED Bricks
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| Russell Nelson <lego-robotics@crynwr.com> wrote in message news:14380.1027.3890...nwr.com... (...) Its not .7 volts for an LED its more like 1.8volts and its takes 20ma if you want for full brightness for a typical display LED. (or more for a (...) (25 years ago, 12-Nov-99, to lugnet.robotics)
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Message is in Reply To:
| | Re: Homemade LED Bricks
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| basicly.. it's i*r=v where i = current in amps and r = resistance in ohms and v = voltage in volts.. so.. If we want to find out the resistor's value.. we re arrange it like so.. r = v/i so 10 millamps (typical led current) = .01 Amps.. And at 9 (...) (25 years ago, 12-Nov-99, to lugnet.robotics)
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