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Re: [TenTec] LED Dropping resister

To: tentec@contesting.com
Subject: Re: [TenTec] LED Dropping resister
From: Ken Brown <ken.d.brown@verizon.net>
Reply-to: tentec@contesting.com
Date: Fri, 19 Dec 2003 11:13:01 -1000
List-post: <mailto:tentec@contesting.com>



R = (Vsupply - Vled) / Iled


R       : resistor value
Vsupply : power supply voltage, must be > Vled
Vled    : voltage drop on LED, generally from 1.6 V to 2.7 V
Iled    : current, try 5 mA = 0.005 A

Example:
 Vsupply = 12 V
 Vled    =  2 V
 Iled    =  5 mA = 0.005 A
 R       = (12 - 2) / 0.005 = 2000 Ohms (use 1800 or 2200 Ohms)



V led and I led are generally available from the manufacturer or vendor of the leds. The LED will not light at all untill the voltage gets up to around V led. When the voltage gets high enough it will start to draw some current, and from that point on as the current goes up so will the brightness. You will want to limit the current to a value no greater than what the manufacturer recommends, so that you don't blow it up. And you may want to limit it to some lower value to get less than maximum brightness.


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