X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 02 Dec 2005 18:17:05 -0500 Message-ID: X-Original-Return-Path: Received: from mta10.adelphia.net ([68.168.78.202] verified) by logan.com (CommuniGate Pro SMTP 5.0.3) with ESMTP id 860293 for lml@lancaironline.net; Fri, 02 Dec 2005 08:39:06 -0500 Received-SPF: pass receiver=logan.com; client-ip=68.168.78.202; envelope-from=glcasey@adelphia.net Received: from [70.34.70.106] by mta10.adelphia.net (InterMail vM.6.01.05.02 201-2131-123-102-20050715) with ESMTP id <20051202133818.KHRQ1186.mta10.adelphia.net@[70.34.70.106]> for ; Fri, 2 Dec 2005 08:38:18 -0500 Mime-Version: 1.0 (Apple Message framework v733) In-Reply-To: References: Content-Type: multipart/alternative; boundary=Apple-Mail-72-604674398 X-Original-Message-Id: <2197B0F0-1685-4068-834D-BB05E67C588A@adelphia.net> From: Gary Casey Subject: Re: LED Position Lights X-Original-Date: Fri, 2 Dec 2005 05:38:16 -0800 X-Original-To: "Lancair Mailing List" X-Mailer: Apple Mail (2.733) --Apple-Mail-72-604674398 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed > re: [LM Regarding using a PWM controller for LED's - this will usually work very well, but it must, I think, be use IN CONJUNCTION with a dropping resistor, not instead. The reason is that the LED is in actuality a forward-biased diode and it has very low resistance. Even a short-duration application of a high voltage will likely destroy the device. As others have suggested you can put them in series to increase the voltage drop, but the bottom line is that the resistor or some other way to limit the current is required. Then you can add the PWM circuit to dim the output from there. If you are really talking about position lights there is no reason to dim them and hence you are back to a dropping resistor as the simplest, most reliable way to control the current. It does waste energy, but I don't know of another (better) way. Gary Casey --Apple-Mail-72-604674398 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=ISO-8859-1
re: [LM


Regarding using a PWM = controller for LED's - this will usually work very well, but it must, I = think, be use IN CONJUNCTION with a dropping resistor, not instead.=A0 = The reason is that the LED is in actuality a forward-biased diode and it = has very low resistance.=A0 Even a short-duration application of a high = voltage will likely destroy the device.=A0 As others have suggested you = can put them in series to increase the voltage drop, but the bottom line = is that the resistor or some other way to limit the current is = required.=A0 Then you can add the PWM circuit to dim the output from = there.=A0 If you are really talking about position lights there is no = reason to dim them and hence you are back to a dropping resistor as the = simplest, most reliable way to control the current.=A0 It does waste = energy, but I don't know of another (better) way.

Gary = Casey
= --Apple-Mail-72-604674398--