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②
Pay attention to the length of time that a switch is ON at an intermediate stroke position.
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:
V(mm/s)= ×1000
③
Keep wiring as short as possible.
<Reed switch>
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 5 m or longer.
2) Even if an auto switch has a built-in contact protection circuit, when the wiring is more than 30 m 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 with
SMC in this case.
<Solid state switch>
3) Although wire length should not affect switch function, use a wire 100 m or shorter.
④
Pay attention to the internal voltage drop of the auto switch.
<Reed switch>
1) Auto switch with an indicator light (Except D-A96 , A96V)
●
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.
Load
●
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 for right (MODEL D-A90 , A90V)
<Solid state switch / 2-wire type>
3) Generally, the internal voltage drop will be greater with a 2 wire solid state auto switch than with a
reed auto switch. Take the same precautions as in 1).
Also, take note that a 12VDC relay is not applicable.
Auto switch operating range (mm)
Time load applied(ms)
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2020-10-13 10:33
DI987004