🚀 go-pugleaf

From: atn@cory.Berkeley.EDU (Alan Nishioka) Message-ID: <17419@pasteur.Berkeley.EDU>

>For a friend's mechanical engineering project I needed a circuit that
>latched.  I built a circuit using two SPDT relays in which power through
>one coil closed a switch which energized the second coil which closed a
>switch which energized the first coil, or something like that :-)  Kinda
>like an RS latch.  This worked fine for my application, except there was
>a condition where if the wrong switch was closed, the system would
>oscillate.

A very common latching circuit (for motor control) is to use one
relay with two sets of contacts. It is a DPDT relay.         ^^^

It requires three wires in the control conduit, two switches: SPST
momentary contact, one normally open and one normally closed.

                    1st set of contacts
                        for control
                         _________                               Hot
                        |         |                        ___    |
          ------o-----------|/|-----------o-------------- .   . --o
          |             |         |                               |
          o-----o-----------| |-----------o-------------- .---. --o
          |             |_________|
          |
          |                  C
          |-----o------------O------------o-----------------------o
                             I                                    |
                             L                                   Gnd
                         _________
                        |         |
                o-----------|/|-----------o
                        |         |
                o-----------| |-----------o
                        |_________|

                    2nd set of contacts
                         for load

-----------symbols used------------

|/| normally closed  contact of relay

| | normally open    contact of relay

.---. normally closed  momentarily opened manually operated switch
 ___
.   . normally open    momentarily closed manually operated switch


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