Technical Guide for Limit Switches
Connections
•
Do not connect a Single Limit Switch to two power supplies that are
different in polarity or type.
•
Do not design a circuit where voltage is imposed between contacts,
otherwise contact welding may result.
•
Do not use a circuit that will short-circuit if an error occurs,
otherwise the charged part may melt and break off.
•
Application of Switch to a Low-voltage, Low-current Electronic
Circuit.
1. If bouncing or chattering of the contacts results and causes
problems, take the following countermeasures.
(a)Insert an integral circuit.
(b)Suppress the generation of pulse from the contact bouncing
or chattering of the contacts so that it is less than the noise
margin of the load.
2. Conventional silver-plated contacts are not suited to this
application. Use gold-plated contacts, which are ideal for
handling minute voltage or current loads.
3. The contacts of the Switch used for an emergency stop must be
normally closed with a positive opening mechanism.
•
In order to protect the Switch from damage due to short-circuits, be
sure to connect a quick-response fuse with a breaking current 1.5
to 2 times larger than the rated current to the Switch in series. When
complying with EN approved ratings, use a 10-A IEC 60269-
compliant gI or gG fuse.
Operating Environment
•
Do not use the Switch by itself in atmospheres containing
flammable or explosive gases. Arcs and heating resulting from
switching may cause fire or explosion.
•
Use protective covers to protect Switches that are not specified as
waterproof or airtight whenever they are used in locations subject
to splattering or spraying oil or water, or to accumulation of dust or
dirt.
•
The materials of Limit Switch may change in quality or deteriorate
if the Limit Switch is used outdoors or any other location where the
Limit Switch is exposed to special machining oil. Consult your
OMRON representative before selecting the model.
•
Be sure to install the Switch so that the Switch is free from dust or
metal powder. The actuator and the switch casing must be
protected from the accumulation of dust or metal powder.
•
Do not use the Switch in locations where the Switch is exposed to
hot water at a temperature greater than 60
°
C or steam.
•
Do not use the Switch under temperatures or other environmental
conditions not within the specified ranges.
The rated permissible ambient temperature range varies with the
model. Refer to the specifications in this catalog. If the Switch is
exposed to radical temperature changes, the thermal shock may
deform the Switch and the Switch may malfunction.
•
Be sure to protect the Switch with a cover if the Switch is in a
location where the Switch may be actuated by mistake or where the
Switch is likely cause an accident.
•
If vibration or shock is continuously imposed on the Switch, contact
failure, malfunction, or decrease in service life may be caused by
abrasive powder generated from the internal parts. If excessive
vibration or shock is imposed on the Switch, the contacts may
malfunction or become damaged. Make sure to install the Switch in
locations free of constant vibration or shock.
•
Do not use the Switch with silver-plated contacts for long periods if
the switching frequency of the Switch is comparatively low or the
load is minute. Otherwise, sulfuric film will be generated on the
contacts and contact failures may result. Use the Switch with gold-
plated contacts or use a dedicated Switch for minute loads instead.
Incorrect
Correct
NC
NO
Connect the load to the same polarities.
NC
NO
Power Connection Examples
(Connection of Different Polarities)
Incorrect
NC
NO
L
L
AC
DC
Incorrect Power Connection Example
(Connection of Different Power Supplies)
There is a risk of AC and DC mixing.
Incorrect
L
100 V
200 V
NC
NO
NC
NO
L
L
Correct
Incorrect
Terminal box
Terminal box
Incorrect
Correct
Separate the Switch
from hot water.
Incorrect
Correct
(Malfunction prevented)
Correct
Incorrect
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