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Figure 50
Memory usagewith blocking signals.
The memory valves in a circuit can be used to manage momentary signals in addition to continuous signals,
specifically those defined as blocking signals. In order to remainwithin a certain time limit which is established by
the necessity of the circuit, also in this casewe use a bistable 3/2-way valvewithmemory function.
The starting condition is;
X
=
1
in the presence of signal
K
, i.e. thememory will have received the signal “
a
”.
The signal
K
, passing through thememory becomes
X
, its duration depends on the arrival of the signal “
b
”.
The signals “
a
” and “
b
”may be short momentary impulses, andmay also be different from one another.
a
X
b
X
K
a
b
duration
of output
K
Fig. 50
a
X
b
X
a
b
durationof output
Fig. 49
The
5/2-way
memoryvalvediffers from the3/2-way in that it has two separateoutlets, eachofwhichmayalternately
assume state
ZERO
or
ONE
.
The signals “
a
” and “
b
” change over thememory outputs “
X
” and “
K
”respectively.
Figure 51
Pos. 1
: if
a
=
0
and
b
=
1
then
K
=
1
and
X
=
0
At the interruption of information “
b
” thememorymaintains (hasmemorized) the position if
a
=
0
and
b
=
0
the
K
=
1
and
X
=
0
Pos. 2
: if
a
=
1
and
b
=
0
then
K
=
0
and
X
=
1
At the interruption of information “
a
” thememorymaintains the position if
a
=
0
and
b
=
0
then
K
=
0
and
X
=
1
The continuous presence of one of the two signals “
a
” or “
b
” does not permit to change the state of thememory.
X
K
X
K
a
(Y)
(K)
(a) (b)
logic
symbol
1
2
a= 0
b=1
b=0
a= 1
Fig. 51
Figure 49
Prolonging the effect of signal “a”
From themanual or mechanical valve, signal “
a
”
reaches pilot port 12 of thememory activating its output.
a
=
1
X
=
1
Upon interruption of signal “
a
”, the output remains active.
a
=
0
X
=
1
To remove the output
X
, signal “
b
” is required.
b
=
1
X
=
0
The duration of output
X
is the period between the arrival of signal “
a
” and signal “
b
”.
Even if signal “
a
” were to be a very short impulse the same rulewould apply. It can be beneficial to represent the
status of the signals and output over time on a diagram. The unit of time is not indicated.
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CIRCUIT TECHNIQUE