VANAGON archives -- May 2012, week 2 (#155)

Date:         Thu, 10 May 2012 07:51:27 -0500
Reply-To:     ddbjorkman@VERIZON.NET
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Bjorkman <ddbjorkman@VERIZON.NET>
Subject:      Re: Charge warning light LED question - David B.
Content-type: text/html; charset=UTF-8

<div style="FONT-FAMILY: Arial; COLOR: #000000; FONT-SIZE: 24px"><DIV><FONT size=2 face=Tahoma>Boy, I love that kind of talk.&nbsp; It's a good thing this list exists.&nbsp;&nbsp;Sometimes the book is just not enough.</FONT></DIV><DIV><FONT size=2 face=Tahoma></FONT>&nbsp;</DIV><DIV><FONT size=2 face=Tahoma>Dave B. (the other one)</FONT></DIV><DIV>&nbsp;</DIV><DIV style="MARGIN: 5px 0px; BORDER-TOP: #bcbcbc 1px solid"></DIV><SPAN style="FONT-FAMILY: arial; COLOR: #000000; FONT-SIZE: 12px">On 05/09/12, <SPAN>David Beierl&lt;dbeierl@ATTGLOBAL.NET&gt;</SPAN> wrote:</SPAN><DIV>&nbsp;</DIV><DIV style="FONT-FAMILY: arial; COLOR: #000000; FONT-SIZE: 12px">At 04:59 PM 5/9/2012, Scott Daniel - Turbovans wrote:<BR>&gt;it works fine.<BR>&gt;I know an LED would be brighter.<BR>&gt;LED's have polarity ..<BR>&gt;so wondering if an LED will work there for a warning light.<BR><BR>You could use an LED the way the Vanagon does, but in addition to the<BR>series resistor for the LED you'd have to add another resistor in<BR>parallel to the <FONT size=2 face=Tahoma>pair</FONT>, to get enough current to excite the<BR>alternator. Take a look at 90.8 fig 4. R3, 150 ohms one watt or<BR>better (notice the space around it) is wired from panel hot to<BR>D+. K2, the indicator LED in series with 470 ohm R4 is also wired<BR>from panel hot to D+. You can see this on 97.91 track 50-51. As of<BR>'87 they apparently changed to two shunt resistors instead of one,<BR>presumably 300 ohms each (97.108 track 50-51). I suspect they did<BR>that because they were getting overheating problems on the flexible<BR>circuit, so they put in two half-watters in parallel to spread out<BR>the heat load a little.<BR><BR>In this setup the 150 ohm resistor is supplying the "tickle" current<BR>to get the alternator going; the contribution from the LED and its<BR>resistor is pretty minor.<BR><BR>Yrs,<BR>d<BR></DIV></div>

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