[Oeva-list] HELP! prescaler in portland

Rick Barnes barnes.rick at comcast.net
Thu Jul 28 05:32:19 PDT 2005


You can connect your link 10 across 24v of your battery pack. This is how
mine is connected.

Also, you can build one yourself (see attachment). It is a simple voltage
divider.

Rick Barnes
Aloha, OR

-----Original Message-----
From: oeva-list-bounces at oeva.org [mailto:oeva-list-bounces at oeva.org] On
Behalf Of Jerry Eaton
Sent: Wednesday, July 27, 2005 6:00 PM
To: oeva-list at oeva.org
Subject: [Oeva-list] HELP! prescaler in portland


Just had a tragic link 10 accident and to make a long story short (yes, pun)
I think my prescaler is fried.  Anyone know where to obtain a 0-500v
prescaler in Portland reasonably priced on short notice?  I'm getting close
to road worthy on my conversion project and would like to have
instrumentation.

Jerry Eaton
'63 VW Ragtop Bug EV (almost there...)

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Yes. I've dissected a 100v prescaler, and at least can tell you what was
in that one. View with fixed-width font:
             _ _
+Battery____| | |_____/\/\_______/\/\______/\/\________E-meter pin 5
          |  L1   |    R1    |    R2    |   R3   |     (+Vsense)
          | open  |   105k   |  11.5k   |  270   |
          |__/\/\_|    1%    |    1%    |   5%   |
             R4             _|_        _|_     \_|_  Q1
           0 ohms        C1 ___     C2 ___      /_\\ Siliconix
             _ _     1000pF  |   0.1uF  |        |   VP0610L
           _| | |_      1KV  |     50v  |        |
          |  L2   | ceramic  | ceramic  |        |
          | open  |          |          |        |
-Battery__|__/\/\_|__________|__________|________|____E-meter pin 1
             R5                                       (-Vsense)
           0 ohms

The only functional parts are R1 and R2, which total up to 118k for a
100v prescaler, or 1057k for a 500v prescaler. Q1 is actually a MOSFET,
but is being used as a low-leakage zener diode to limit the max output
voltage to about 50v.

If your prescaler output is reading ~290v, most likely Q1 is blown. This
can happen if you connect the prescaler output to battery pack postive
by mistake.
-- 
Lee A. Hart                Ring the bells that still can ring
814 8th Ave. N.            Forget your perfect offering
Sartell, MN 56377 USA      There is a crack in everything
leeahart_at_earthlink.net  That's how the light gets in - Leonard Cohen


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