8. Keep wiring as short as possible.
<Reed>
As the length of the wiring to a load gets longer, the rush current at switching ON becomes
greater,
and this may shorten the product
’s life. (The switch will stay ON all the time.)
1) Use a contact protection box when the wire length is 5m or longer.
2) Even if an auto switch has a built-in contact protection circuit, when the wiring is more than
30m
long, it is not able to adequately absorb the rush current and its life may be reduced.
It is again necessary to connect a contact protection box in order to extend its life. Please consult
SMC in this case.
<Solid state>
Be sure to use a wire length 100m or less.
When the wire length is long, we recommend the ferrite core should be attached to the both ends of
the cable to prevent excess noise. A contact protection box is not necessary for solid state switches
due to the nature of this product construction.
9. Do not use a load that generates surge voltage.
<Reed>
If a surge voltage is generated, the discharge occurs at the contact, possibly resulting in the shortening
of product life.
If driving a load such as a relay that generates a surge voltage, use an auto switch with built-in contact
protection circuit or use a contact protection box.
<Solid state>
If driving a load such as a relay that generates a surge voltage, use a built-in surge absorbing element
type device.
10. Pay attention to the internal voltage drop of the auto switch.
<Reed>
1) Auto switch with an indicator light
・
If auto switches are connected in series as shown below, take note that there will be a large voltage
drop because of internal resistance in the light emitting diodes. (Refer to the internal voltage drop in
the auto switch specifications.)
[The voltage drop will be
“n” times larger when “n” auto switches are connected.]
Even though an auto switch operates normally, the load may not operate.
・
In the same way, when operating under a specified voltage, 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.
Supply Internal voltage Minimum operating
voltage drop of auto switch voltage of load
2) If the internal resistance of a light emitting diode causes a problem, select an auto switch without an
indicator light.
<Solid state / 2-wire type>
Generally, the internal voltage drop of the solid state auto switch is larger than that or the reed auto
switch. When the auto switches (“n” pcs.) are connected in series, the voltage drop is multiplied by “n”.
In this case, the auto switches operate correctly, but the loads may not operate. Additionally, note that
the 12 VDC relay does not apply to the auto switch.
-11-
>
2020-10-13 10:36
DI987004
