E2E2-WIREAC
E2E2-WIREAC
16
JCONNECTING LOAD TO AC 2-WIRE
SENSOR
Refer to the following before using AC or DC 2-wire Proximity Sen-
sors.
Surge Protection
Although the Proximity Sensor has a surge absorption circuit, if
there is any machine that has a large surge current (e.g., a motor or
welding machine) near the Proximity Sensor, connect a surge ab-
sorber to the machine.
Leakage Current
When it is OFF, the Proximity Sensor has leakage current. Refer to
Leakage Current Characteristics. In this case, the load is imposed
with a small voltage and the load may not be reset. Before using the
Proximity Sensor, make sure that this voltage is less than the load
reset voltage. The AC 2-wire Proximity Sensor cannot be con-
nected to any card-lift-off relay (e.g., the G2A) because contact
vibration of the relay will be caused by the leakage current and the
life of the relay will be shortened.
Countermeasures Against Leakage Current
AC 2-wire Models
Connect a bleeder resistor as the bypass for the leakage current so
that the current flowing into the load will be less than the load reset
current.
As shown in the following diagram, connect the bleeder resistor so
that the current flowing into the Proximity Sensor will be 10 mA mini-
mum and the residual voltage imposed on the load will be less than
the load reset voltage.
Load
Bleeder resistor R
VAC power
supply VS
Refer to the following to calculate the bleeder resistance and the al-
lowable power of the bleeder resistor.
R≦VS/(10 -- I) (kΩ)
P>V
S2/R (mW)
P: The allowable power of the bleeder resistor. (The actual power
capacity of the bleeder resistor must be at least a few times as
large as the allowable power of the bleeder resistor.)
I: Load current (mA)
The following resistors are recommended.
100 VAC (supply voltage): A resistor with a resistance of 10 kΩmax-
imum and an allowable power of 3 W minimum
200 VAC (supply voltage): A resistor with a resistance of 20 kΩmax-
imum and an allowable power of 10 W minimum
If these resistors generate excessive heat, use a resistor with a re-
sistanceof10kΩmaximum and an allowable power of 5 W mini-
mum at 100 VAC and a resistor with a resistance of 20 kΩmaximum
and an allowable power of 10 W minimum at 200 VAC instead.
JPRECAUTIONS FOR AC 2-WIRE PROXIMITY SENSORS IN OPERATION
Connector
Model Connection type Method Description
AC
2-wire
AND
(serial connection) Load
Load
Load
Vs≧100 V
Incorrect
Correct
If 100 or 200 VAC is imposed on the Proximity
Sensors, VL(i.e., the voltage imposed on the
load) will be obtained from the following.
VL=V
S-- (residual voltage x no. of Proximity
Sensors) (V)
Therefore, if VLis lower than the load operating
voltage, the load will not operate.
A maximum of three Proximity Sensors can be
connected in series provided that the supply
voltage is 100 V minimum.