Auto Switch Precautions 1
Be sure to read before handling.
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Read the specifications carefully and use this product appro-
priately. The product may be damaged or malfunction if it is
used outside the range of specifications of load current,
voltage, temperature or impact.
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are used close together.
When two or more cylinders with auto switches are lined up in
close proximity to each other, magnetic field interference may
cause the switches to malfunction. Maintain a minimum
cylinder separation of 40 mm.
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When an auto switch is placed at an intermediate position of
the stroke and a load is driven at the time the piston passes,
the auto switch will operate, but if the speed is too great, the
operating time will be shortened and the load may not operate
properly. The maximum detectable piston speed is:
In case of a high piston speed, it is possible to extend the
operating time of the load by using an auto switch (F5NT) with
a built-in off delay timer (approximately 200 ms).
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<Reed switches>
As the length of the wiring to a load gets longer, the rush
current at switching ON becomes greater, and this may
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time.)
1) For an auto switch without a contact protection circuit, use a
contact protection box when the wire length is 5 m or
longer.
2) Even when an auto switch has a built-in contact protection
circuit, if the lead wire length is 30 m or more, the rush
current cannot be adequately absorbed and the life of the
switch may be shortened. Contact SMC, as it is also
necessary in this case to connect a contact protection box
to extend the switch life.
<Solid state switches>
3) Although wire length should not affect switch function, use a
wire that is 100 m or shorter.
5.
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switch.
<Reed switches>
1) Switches with an indicator light
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take note that there will be a large voltage drop because
of internal resistance in the light emitting diodes. (Refer to
internal voltage drop in the auto switch specifications.)
[The voltage drop will be “n” times larger when “n” auto
Design and Selection
Auto switch operating range (mm)
Load operating time (ms)
x 1000
V
(mm/s) =
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although an auto switch may operate normally, the load
may not operate. Therefore, the formula below should be
satisfied after confirming the minimum operating voltage
of the load.
2) If the internal resistance of a light emitting diode causes a
problem, select a switch without an indicator light (Model
D-A6
씲
, D-Z80).
<Solid state switches>
3) Generally, the internal voltage drop will be greater with a
2-wire solid state auto switch than with a reed switch. Take
the same precautions as in 1).
Also note that a 12 VDC relay is not applicable.
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<Solid state switches>
With a 2-wire solid state auto switch, current (leakage current)
flows to the load to operate the internal circuit even when in
the OFF state.
If the condition given in the above formula is not met, it will not
reset correctly (stays ON). Use a 3-wire switch if this specifi-
cation cannot be satisfied. Moreover, leakage current flow to
the load will be “n” times larger when “n” auto switches are
connected in parallel.
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<Reed switches>
If driving a load such as a relay that generates a surge
voltage, use a switch with a built-in contact protection circuit or
use a contact protection box.
<Solid state switches>
Although a zener diode for surge protection is connected at
the output side of a solid state auto switch, damage may still
occur if the surge is applied repeatedly. When a load, such as
a relay or solenoid, which generates surge is directly driven,
use a type of switch with a built-in surge absorbing element.
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When an auto switch is used for an interlock signal requiring
high reliability, devise a double interlock system to avoid
trouble by providing a mechanical protection function, or by
also using another switch (sensor) together with the auto
switch.
Also perform periodic maintenance inspections and confirm
proper operation.
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When designing an application, be sure to allow sufficient
clearance for maintenance and inspections.
Load
Warning
Series
CHS
Supply
voltage
Internal voltage
drop of switch
Minimum operating
voltage of load
–
>
>
Operating current of
load (OFF condition)
Leakage
current
31
