From: ReganRanch@aol.com
Message-ID: <15faf96b.360d10ac@aol.com>
Date: Sat, 26 Sep 1998 12:05:00 EDT
To: lancair.list@olsusa.com
Subject: Transient Absorbers
Mime-Version: 1.0

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Marv Asks:

<< Regarding the use of MOV's (metal oxide varistors) to stop the arcing of
 switch contacts which control solenoid coils, do they get mounted across
 the coil terminals (as in the sketch Ed provided of alternatively using
 flyback diodes) or the switch terminals?  Which works better (diodes vs
 MOV) or are they about equal?  And how do you size the MOV's... there are
 all sorts of specifications when I look in the catalogues for them, how do
 I know which one is right for the task at hand? >>

Diodes work fine but MOVs have a lot more capacity (How 'bout 2000 amps) and
are not polarized. I used a 20 mm diameter 47 volt ZNR type (Don't confuse
with Zener) available in the DigiKey (800 344 4539) catalog part #P7148.
Anything close to these specs will work but you want the voltage rating to be
about 2x the system voltage.

Happy damping.
Brent