5
Electrical Operation of the Relay
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U n lik e the pushbutton w hich must be operated m an u a lly, the
re la y can be operated e le c t r ic a lly . Each re la y has a round
w hite c o il, located to the le ft of the arm s. This is an e le ctro
magnet w hich becomes magnetized when e le c tric current flows
through the c o i l . When the co il becomes "e n e rg iz e d ," the e le ctro
magnet attracts the metal bar connected to the arms (by the p lastic
crossbar) and pulls it to the le f t . Sending current through
the co il of the electro-m agnet operates the re la y s.
—
Thus, the re la y may be operated e le c t r ic a lly without
touching it p h y s ic a lly , but the pushbutton must
be operated m an u ally.
^
The re la y is turned O N by connecting the re la y co il in
a closed e le c tric c ir c u it . When the c irc u it is closed current
OO
flows through the co il and the co il is "e n e rg iz e d ."
Terminals fv opera-he
i
Relay
Switches
———
jm m .
j
/
~Jethr\in2ls Connected
~h Switches
“
USHT
% !?
Three term inals are located d ire c tly above
_
each re la y on the computer p a n e l. These
OO
o O \
.
.
7
i
i
i
i
H
J
term inals are connected under the panel to
the re la y c o il. Two term inals are connected
A .
d ire c tly to the re la y c o il, and the third
OO
J
terminal is connected to a light w ired in
t-
N /
series w ith the re la y co il as shown.
——
When the re la y co il is energized
by connecting power to C and F ,
the lig h t d ire c tly below the re la y comes
O N because the lig h t is w ired in series
w ith the re la y c o il. If the re la y co il is
energized by supplying power through contacts
E and F , the light beneath the re la y w ill N O T
come on because there is no current flowing through
the lig h t. The lig h t below the re la y coil may be used to
show when the re la y is O N .
The c irc u it drawing for a re la y sw itch looks lik e this:
m*00
The follow ing experiments demonstrate re la y operation
w ith pushbuttons and lights in simple computer circu its
Rfi-tay
Switches
A lw a Y S
operate together
Summary of Contents for Minivac 601
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