SEO Version
COLUMN (example)
LS 2 c ) t S3 1 '
1
1
=
Column A
0If
On
H
L
ROW (example)
Off
On
To turn a lamp On , the proces sorsends a signal to the UNL-2803causingthe output to toggle . Poi nt
"A" of the column circuit drops low . Th is causes the TI Pl07 tran sis tor to conduc t
+
l8V and po int
"B" change s to a high state . At the same time, point "G"of the row circuit receivesa low signal
from the processor, which causes the ou tput of the 74LS74 ,at po int "F" ,to go high . A high state at
po int "F" causes the TIP102 trans istor to conduct and the collector of the tran sisto r at po int "E"
changes to a low state . When there is a high state on po int "B"of the column circu itand a low state
at poi nt "E"of the row circuit at the same time , the correspondin glamp is lit.
Normally the micropro cessorshut s Of f the lamp circu it by changing poin t"G"to a high state .
However, in overcurrent conditions the lamp circu itis shut Off through the comparator. Wh ilethe
lamp is On , the .2.Qresistor acts as a current sensor and the lK.Qresistor and .22) .lfcapacitor
together act as a filter. These compo nentsmonitor the row circu it and send a voltage signal to
point "D",the - input ofa LM339 compar ator . If the vol tageat "D"rises above 1.4Vthe output of the
LM339 at po int CC" changes to a low sta te, which is fed ba ck to the 74LS74 and shu ts the row circu it
Off. Once the row is shut Off throug h the comparator circu it,the proce ssormust sign al the 74LS 74
to enab le the row circuit again.
9
7
6
5
4
3
2
I
.. !..il ....
I
IV~ I-r:;I iIY Cn lumna
IV~I -vin
J: n~u nn
7
II~'
_'"
.- n " n n '"
II~'
_"PN
.-0 um n C;
III"
-RI I(
( 'o lu mn4
Y~I-nPN
J: nl umn
:3
Iv<,
_p~n
. -o lu• .• .•••. ,
lvI"
·RP N
( 'al um• •
P~r l-RPN Raw I
I I ' 21 31 41 5I 61 71 el
IIiI "n-RI I( I<ow?
t 2' 22 32 42 52 52 72 62
IiIF rl-rllilN Raw 3
13 23 33 43 53
63
73 63
.I
iRED-YEl _Ro_w_4 14 24 34 44 }4 64 74 64
IRF D-r.I<N_Raw5
15
J5
35 45
}5
65 75 es
.I
IRFD -BlU Row 6
16 26 36 46 56 65 75 65
L
Ip~l\_v,n
I<"w 7
17 27 37 47 57 67
77
B7
IRFn-r.RY Raw B Ie 26 36 46 56
6B
76 Be
L.:..
2
5
6
7
B
9
3-9
Powered by FlippingBook Publisher