Date:         Thu, 18 Nov 1999 10:18:51 -0500
Reply-To:     David Beierl <dbeierl@IBM.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@IBM.NET>
Subject:      Re: high beam indicator
Comments: To: eric.henning@US.ABB.COM
In-Reply-To:  <8525682D.0043F0FA.00@abb-us01-ussmtp.abb.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 07:24 11/18/99 , Eric Henning wrote:
>Another listee wrote it was a incand. bulb.  VW must have switched at some
>point.

They did.  Not sure when -- Bentley shows the '80-'84 US model with a green
LED, Canadian model with a blue incandescent.  My '84 US model has blue
incandescent. I should have said "if it's blue, it's an incandescent."

>on the foil.  So all you need is a standard LED with two wire leads coming off
>it.  LED's
>conduct only one way so if it doesn't light, remove and install the leads the
>other way around.

If the original was an incandescent,  you'll get a surprise when you plug
an LED in.  Well, it won't be a surprise: the LED will burn out.  To use an
LED successfully you need to change the resistor in series with the bulb to
roughly 500-1000 or more ohms.  To get an exact figure the formula is:

R[ohms] = (Vmax[volts] - Vfwd[volts]) / Ifwd[milliamps]

Where R is the desired value of limiting resistor, Vmax is the maximum
charging voltage in the system, Vfwd is the rated forward voltage of the
particular LED in use (typically about 2.2 volts for green, could be as
much as 5-6 volts for blue), and Ifwd is the desired operating current
(which controls brightness).

Since you probably want to choose the brightness in practice, you would
figure out the minimum resistor needed to avoid burning out the LED, then
add resistance until the intensity comes down to what pleases you.  If it's
not bright enough to start with, you need a different LED.

Probably more than you want to know about LEDs and lights in general is at:
http://www.misty.com/~don/index.html

david
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"