1. Keep wiring as short as possible. 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. 2. Do not use a load that generates surge voltage. 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. 3. Pay attention to the internal voltage drop of the auto switch. 1) Auto switch with an indicator light (Except D-A56, A76H, A96, A96V, C76, E76A, Z76) . 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. 2) If the internal resistance of a light emitting diode causes a problem, select an auto switch without an indicator light (D-A6�ｭ, A80, A80H, A90, A90V, C80, R80, 90, 90A, E80A, Z80). Caution 1. Do not allow short-circuit of loads. If the power is turned ON with a load in a short circuited condition, the auto switch will be instantly damaged because of excess current flow into the switch. 2. Avoid incorrect wiring. A 24 VDC auto switch with indicator light has polarity. The brown lead wire or terminal No. 1 is (+), and the blue lead wire or terminal No. 2 is (.). [For D-97, (+) is on the no-displayed side, (.) is on the black line side.] 1) If connections are reversed, an auto switch will operate, however, the light emitting diode will not light up. Also, take note that a current greater than that specified will damage a light emitting diode and it will no longer operate. Applicable model: D-A73, A73H, A73C, A93, A93V, A53, A54, B53, B54, C73, C73C, E73A, Z73, D-R73, R73C, 97, 93A, A33, A34, A33A, A34A, A44, A44A 2) When using a 2-color indicator type auto switch (D-A79W, A59W and B59W), the auto switch will constantly remain ON if the connections are reversed. Reed Auto Switches Precautions Be sure to read this before handling. Supply voltage . Internal voltage > drop of auto switch Minimum operating voltage of load Load Design/Selection Caution 1. Do not use in an environment where there is excessive impact shock. When an excessive impact (300 m/s2 or more) is applied to a reed auto switch during operation, the contact point will malfunction and generate or cut off a signal momentarily (1 ms or less). If a further excessive impact is applied, the reed auto switch may break. Please consult with SMC if a solid state auto switch can be used according to the environment. Operating Environment Caution 1. The protective cover supplied with the product when D-A9�ｮ, A9�ｮV, Z7�ｮ or Z80 is shipped from the factory is intended to absorb the impact generated by handling and prevent the auto switch holding screw from falling. Do not remove this cover until immediately before installing the auto switch on the cylinder or actuator. Caution Wiring Handling Precautions 17 A