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Article #285Re: Best way to power array of LEDs?
From: Grog
Date: Fri, 04 Oct 2002 14:19
Date: Fri, 04 Oct 2002 14:19
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2662 bytes
"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> wrote in message news:B7hloTAPDZn9EwGz@jmwa.demon.co.uk... > I read in sci.electronics.design that Uwe Zimmermann <uwezi@kth.se> > wrote (in <3D9D5939.CD795C11@kth.se>) about 'Best way to power array of > LEDs?', on Fri, 4 Oct 2002: > >You then connect the drain of the transistor to the positive supply and > >the gate/source to the anode of the first LED in each chain. The cathode > >of the last LED is connected to the negative supply. > > This is an *extremely* unreliable circuit, because it has no protection > against the large transients, of both polarities, that occur on vehicle > electrical supplies. > > Don't bother with adding transistors just to get rid of a few resistors > (or maybe add a few more, and MOVs and capacitors and fuses ...). KISS! > -- I'm with you John, "Load Dump" is my favourite automotive electrical term. Something like 40V transients? Make that MOV a big one, preferably after the fuse &|| resistors.. ;-) Be well, Greg the Grog
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X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 112d1e,4ef4c9d4aea85e1f X-Google-Attributes: gid112d1e,public X-Google-Thread: 1131b0,4ef4c9d4aea85e1f X-Google-Attributes: gid1131b0,public X-Google-Thread: 1118be,4ef4c9d4aea85e1f X-Google-Attributes: gid1118be,public X-Google-Thread: 103407,4ef4c9d4aea85e1f X-Google-Attributes: gid103407,public X-Google-Thread: 10d137,4ef4c9d4aea85e1f X-Google-Attributes: gid10d137,public X-Google-ArrivalTime: 2002-10-04 07:19:29 PST Path: arc1-ca.pugleaf.net!archiver1.google.com!news1.google.com!newsfeed.stanford.edu!newsfeed.berkeley.edu!ucberkeley!intgwpad.nntp.telstra.net!news.telstra.net!news-server.bigpond.net.au!not-for-mail From: "Grog" <shem_an_na@SPAM_ME_NOThotmail.com> Newsgroups: sci.electronics.components,sci.electronics.design,alt.engineering.electrical,aus.electronics,sci.electronics.repair References: <0001HW.B9C26E7400A7161B165FEAC0@news.covad.net> <3D9D32DE.93168158@autometer.de> <3D9D5939.CD795C11@kth.se> <B7hloTAPDZn9EwGz@jmwa.demon.co.uk> Subject: Re: Best way to power array of LEDs? Lines: 26 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Message-ID: <Qrhn9.27982$kd3.80464@news-server.bigpond.net.au> Date: Fri, 04 Oct 2002 14:19:28 GMT NNTP-Posting-Host: 144.136.239.69 X-Complaints-To: news@bigpond.net.au X-Trace: news-server.bigpond.net.au 1033741168 144.136.239.69 (Sat, 05 Oct 2002 00:19:28 EST) NNTP-Posting-Date: Sat, 05 Oct 2002 00:19:28 EST Organization: BigPond Internet Services (http://www.bigpond.net.au)