Datasheet

Photomicrosensors
29
● Design Considerations
Influence of Power Supply and Cable Length (EE-SP
Models)
When using a Sensor with a model number beginning with
EE-SP with light modulation, make sure that the power and
cable length are considered in the design. These models are
more easily influenced than models with direct light
modulation (i.e., Sensors with model numbers beginning with
EE-SX or EE-SY).
• Sensors with light modulation that are easily affected:
EE-SPX301/401, EE-SPY30@/40@,
EE-SPZ301@/401@, EE-SPY31@/41@
EE-SPX303/403, EE-SPW311/411,
EE-SPX74@/84@, EE-SPX@@@-W
• Sensors with light modulation that are not easily affected:
EE-SPX613, EE-SPY801/802
∗ All Sensors with model numbers beginning with EE-SX
and EE-SY without light modulation are not easily
influenced by power or cable length.
Reasons for Interference from Power and Cable Length
on Models with Light Modulation
The emitter LED is lit using pulses for models with light
modulation. As a result, the large current required to emit
light from the LED will produce pulsation in the current
consumption. Photoelectric Sensors have built-in
capacitors with sufficient capacity. Therefore, these
Sensors are not influenced by pulsating current
consumption. Incorporating built-in capacitors with
sufficient capacity in compact Photomicrosensors,
however, is difficult, thereby resulting in pulsating current
consumption. Operation may not be able to keep up with
the pulsation in the current consumption depending on the
cable length and the type of power supply used, and this
may result in unstable operation.
Countermeasures
Adding a Capacitor
Attach a capacitor (e.g., film capacitor) of 10 μF min. to the
wires as close as possible to the Sensor. (Use a capacitor
with a dielectric strength that is at least twice the Sensor's
power supply voltage. Do not use tantalum capacitors.
Short-circuit malfunctions may result in the capacitor
igniting due to the large current flow.)
Cable Length
• Design the configuration using a total cable length of 2 m
max. for the Sensor.
• To use a cable longer than 2 m, attach a capacitor with a
capacitance of approximately 10 μF to the wires as shown
below (the distance between the terminal and the capacitor
must be within 2 m). Make sure that the total cable length is
no longer than approximately 5 m. To use a cable length
longer than 5 m, use a PLC or other means to read the
sensor output and then transmit the signals using a PLC
with communications functions. Although cables can be
extended longer than 5 m, performance will be affected by
the noise interference from adjacent cables and other
devices and the influence of cable specifications. Voltage
drops due to resistance in wiring materials will also
influence performance. Therefore, factors, such as the
difference in voltage between the end of the cable and the
sensor and noise levels, must be given full consideration.
Note: Refer to the precautions for the Sensor being used before extending
cables. The length that cables can be extended depends on the Sensor
model and cable specifications. EE-SX, EE-SY, and all other Sensors
without light modulation are not easily affected by cable length (effective
extension from 20 to 50 m is possible).
Emitter
(LB)
Main
circuit
5 to 24 VDC
10 μF
min.
Cur-
rent
Vcc
OUT
GND
2 m max.
Capacitance of
10 μF min.
12 to 24 VDC
0 V
Extension cable
OUT