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Relays?

To: mgs@autox.team.net
Subject: Relays?
From: Bill Evans <evans@c4west.eds.com>
Date: Fri, 10 Nov 1995 9:08:06 PST
Sean "electrically challenged" Johnson wrote:
Would some kind soul who understands electrons and their interaction with the
"smoke" concept kindly draw out in ascii graphics a simple non-relay, and a
simple relay circuit? 

Well, it's been forever since I had one apart, but I'll give it a go.


                      /   (SWITCH)
             |-------/   O---------|
             |                     |--------)
           -----                           ( )
            ---  (BATTERY)         |--------)
           -----                   |     (LIGHT)
            ---                    |
             |                    ///
            /// (GROUND)

            NON-RELAY CIRCUIT (very simple)
                            
            The total current the light (or other device) draws
            goes thru the connecting wires and switch in the 
            circuit.  Which means that everything must be rated
            for the amount of current the light draws.  The new
            flamethrower lights generally use much more current
            than the old sealed beams, so all the wiring and 
            switches really should be upgraded (tough to do on
            any car and keep it looking original).
            
                    
 =====================================================================

             ------------------|
             |        /        |
             |-------/   O---| |      ____
             |        (SW)   | |      |   |--------)
           -----            -- |      |           ( )
     (BATT) ---      (RELAY)|| \ o-----   |--------)
           -----            -- (contacts) |     (LIGHT)
            ---              |            |
             |              ///          ///
       (GND)///  

            RELAY CIRCUIT

            The relay part of this circuit, draws a small amount
            of current to operate the coil in the relay.  The
            contacts of the relay and the separate wiring handle
            the full load of the light or other device.

            Basically, this means that only the relay contacts and 
            connecting wiring must be rated for the load that you 
            are going to use.

            Relays operate like an electro magnet.  As current goes 
            thru the coil, the contacts are closed.  Remove the 
            current, they spring open.
 
I have seen relay circuits used on horns, lights and starters. 

--
# Bill Evans                206-562-4505, FAX-206-562-4509 
# Systems                             evans@c4west.eds.com
# Looking for my first car again: a 1953 MGTD

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