Pneumatic Clean Series

24Auto Switch/Common Precautions 1Be sure to read before handling. Refer to pages 7 to 16 of Front matter for safety instructions andcommon precautions for clean series. Refer to the main text for precautions for each series.WarningqConfirm the specifications.The product may be damaged or malfunction if it is used outsidethe specified range of current load, voltage, temperature or impact.wTake precautions when multiple cylinders are usedclose together.When multiple auto switch cylinders are used in closeproximity, magnetic field interference may cause the switchesto malfunction. Design a minimum interval of 40mm betweenthe cylinder tubes. (When the allowable interval is indicated foreach cylinder series, use the specified value.)ePay attention to the length of period when the switchis ON at an intermediate stroke position.In case an auto switch is placed at an intermediate position ofthe stroke and the load is supposed to be driven while thepiston passes, an excessively high piston speed may not allowenough time for the load to operate, even though the autoswitch will operate. The maximum detectable piston speed isV (mm/s)=Auto switch operation range (mm)X 1000Load operation time (ms)For a high piston speed, auto switches with built-in off delaytimer (approx. 200ms) (D-F5NT, F7NT, G5NT and M5T) canbe used to extend the load operation time.rKeep the wiring as short as possible.The rush current at the time of switching ON increases with thelength of wiring to the load, which may shorten the product's life(The switch will stay ON all the time).1)For an auto switch without a contact protection circuit, use acontact protection box when the wire length is 5m or longer.2)Even when an auto switch has a built-in contact protectioncircuit, with a lead wire length of 30m or longer, the rush currentmay not be adequately absorbed and the life of the switch maybe shortened. Contact SMC in such a case, as it will benecessary to connect a contact protection box to extend the lifeof the switch.3)Although the length should not affect the switch function, usea wire of 100m or shorter.tWatch for internal voltage drops of the switch.1)Switches with indicator light (Not including Models D-A56,A76H, A96, A96V, C76, E76A and Z76).If auto switches are connected in series as shown below,take note that there will be a large voltage drop because ofinternal resistance of the light emitting diode. (Refer to theinternal voltage drop in the auto switch specifications.)[If n pieces of auto switches are connected, the pressure dropwill be n times as large.]Although the auto switch may operate normally, the load mayLoadDesign • SelectionIn the same way, when operating below the specifiedvoltage, although an auto switch may operate normally, theload may not operate. Therefore, the formula below should besatisfied after confirming the minimum operating voltage ofthe load.Supplyvoltage–Internal voltagedrop of switchMinimum operatingvoltage of load2)If the internal resistance of the light emitting diode causes aproblem, select a switch without an indicator light (Models: D-A6, A80, A80H, A90, A90V, C80, R80, 90, E80A, Z80).3)Generally, the internal voltage drop will be greater with a 2wire solid state auto switch than with a reed switch. Take thesame precautions as in 1).Also, note that a 12VDC relay is not applicable.yTake precautions against leakage current.With a 2 wire solid auto switch, current (leakage current) flowsto the load to operate the internal circuit even when the switchis OFF.Operating current of load> Leakage current(Input OFF current of controller)If the above condition is not met, the switch will not be resetproperly (will stay ON). Use a 3 wire switch if the specificationis not satisfied.The leakage current flow to the load will be "n" times as largewhen "n" pieces of auto switches are connected in parallel.uDo not use a load that generates surge voltage.When driving a load that generates a surge voltage, such as arelay, use a switch with a built-in contact protection circuit oruse a contact protection box.Although a zener diode for surge protection is connected at theoutput side of a solid state auto switch, damage may still becaused if the surge is applied repeatedly. When a load, such asa relay or solenoid, which generates surge is driven directly,use a switch with a built-in surge absorbing element.iCaution for use in an interlocking circuitWhen an auto switch is used for an interlock signal requiringhigh reliability, devise a double interlock system to avoid troubleby providing a mechanical protection function or by also usinganother switch (sensor) together with the auto switch.At the same time, perform periodic inspections to confirmproper operation.oEnsure sufficient clearance for maintenance activities.When designing an application, be sure to allow sufficient clearancefor maintenance and inspections.>Actuator5