Sysmac CPM1A-20CAR-A, Operation Manual

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43
Leakage Current (24 VDC)
A leakage current can cause false inputs when using 2-wire sensors (proximity
switches or photoelectric switches) or limit switches with LEDs.
False inputs won’t occur if the leakage current is less than .75 mA, but if the leak-
age current exceeds these values, insert a bleeder resistor in the circuit to re-
duce the input impedance, as shown in the following diagram.
R
CPM1A
Input power
supply
Bleeder resistor
2-wire sensor, etc.
I: Device’s leakage current (mA)
R: Bleeder resistance (k
W
)
W: Bleeder resistor’s power rating (W)
The equations above were derived from the following equations:
L
C
: CPM1A’s input impedance(k
W
)
I
C
: CPM1A’s input current (mA)
E
C
: CPM1A’s OFF voltage (V) = 5.0V
R
=
L
C
×
5.0
I
×
L
C
5.0
k max. W
=
2.3
R W min.
Refer to NO TAG I/O Specifications for details on the values L
C
, I
C
, and E
C
.
Theinputimpedance,inputcurrent, andOFF voltagemay vary depending onthe
input being used. (IN00000 through IN00002 have different values.)
Input voltage V
c
(24)
Input current I
c
Input voltage V
c
(24)
Input current I
c
£
Off voltage (E
c
)
l x
Input voltage V
c
R
x Input voltage (V
c
) x tolerance (4)
V
c
:CPM1A’s input voltage(V)
R x
R +
W ³
Leakage Current (120 VAC)
Due to the high impedance of the 120 VAC inputs, the input may not draw
sufficient current for some 2-wire sensors to operate properly. Insert a bleeder
resistor to reduce the input impedance.
The above equations, modified for 120 VAC, become:
R
=
L
C
×
25.0
(I
×
L
C
) 25.0
k max. W
=
57.6
R W min.
Inductive Loads
When connecting an inductive load to an input, connect a diode in parallel with
the load. The diode should satisfy the following requirements:
1, 2, 3...
1. Peak reverse-breakdown voltage must be at least 3 times the load voltage.
2. Average diode rating for rectified current must be at least 1 A.
IN
COM
Diode
CPM1A
Wiring and Connections
Section 1-4