dc touch control switch with delayed off application note 706

APPLICATION
NOTE
706
LSI/CSI
UL
®
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747
(631) 271-0400 FAX (631) 271-0405
A3800
DC TOUCH CONTROL SWITCH WITH DELAYED OFF
November 1998
Touching the Touch Plate initiates negative-going pulses
at LS7539 - Pin 8 (OUT). This triggers the One-Shot
causing 556 - Pin 9 (ONE-SHOT Output) to go high.
The One-Shot Output (556-9) turns on Q1, resetting
OUT (LS7539-8) to a high. At the end of the OneShot, the Touch Plate is ready to be activated again.
+V
+
1µF
-
10M
1
2
DISCH
THR
R2C2 =
+V
CMOS 556
V DD
DISCH
t
1.1
R2
14
13
OUT
3
8
OUT
7
V SS
6
CV
5
MODE
CONT
4
+V
THR 12
C2
RESET
CV
11
LS7539
5
60Hz
CLOCK SYNC
1
2
V DD
TOUCH
4
3
OUT
R1
C1
270K
+V
+V
R1C1 =
1
1.4 X 60
6
TRIG
RESET
OUT
7
Vss
10
+V
9
8
TRIG
60Hz (556-5)
1K
OUT (7539-8)
Q1
1000pF, 1KV
ONE-SHOT
51K
1000pF, 1KV
TOUCH PLATE
ONE-SHOT
(556-9)
709-111198-1
t