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Installation and Maintenance Manual
Solid State Auto-Switch Series D-H7A1, D-H7A2,
D-H7BA, D-H7B, D-H7BW, D-H7NW, D-H7PW

This manual should be read in conjunction with the current product catalogue

For future reference, please keep this manual in a safe place

Safety Instructions

These safety instructions are intended to prevent a hazardous situa-
tion and/or equipment damage. These instructions indicate the level
of potential hazard by label of “Caution”, “Warning” or “Danger”.
To ensure safety, be sure to observe ISO4414 

(Note1)

, JIS B 8370 

(Note2)

and other safety practices.
Note 1: ISO 4414: Pneumatic fluid power – Recommendations for the
application of equipment to transmission and control systems.
Note 2: JIS B 8370: Pneumatic system axiom.

CAUTION :

Operator error could result in injury or

equipment damage.

WARNING :

Operator error could result in serious

injury or loss of life.

DANGER :

In extreme conditions, there is a 

possible result of serious injury or loss of life.

WARNING

1. The compatibility of pneumatic equipment is the respon-

sibility of the person who designs the pneumatic system
or decides its specifications.

Since the products specified here are used in various operating
conditions, their compatibility for the specific pneumatic system
must be based on specifications or after analysis and/or tests to
meet your specific requirements.

2. Only trained personnel should operate pneumatically

operated machinery and equipment.

Compressed air can be dangerous if an operator is unfamiliar 
with it. Assembly, handling or repair of pneumatic systems should
be performed by trained and experienced operators.

3. Do not service machinery/equipment or attempt to

remove component until safety is confirmed.

1)  Inspection and maintenance of machinery/equipment should

only be performed after confirmation of safe locked-out 
control positions.

2)  When equipment is to be removed, confirm the safety process

as mentioned above. Switch off air and electrical supplies and
exhaust all residual compressed air in the system.

3)  Before machinery/equipment is re-started, ensure all safety

measures to prevent sudden movement of cylinders etc.
(Bleed air into the system gradually to create back-pressure,
i.e. incorporate a soft-start valve).

4. Contact SMC if the product is to be used in any of the 

following conditions:

1)  Conditions and environments beyond the given specifica-

tions, or if product is used outdoors.

2)  Installations in conjunction with atomic energy, railway, air

navigation, vehicles, medical equipment, food and beverage,
recreation equipment, emergency stop circuits, press 
applications, or safety equipment.

3)  An application which has the possibility of having negative

effects on people, property, or animals, requiring special 
safety analysis.

CAUTION

Ensure that the air supply system is filtered to 5 micron.

1. Product specification

Model number

D-H7A1

D-H7NW

D-H7A2

D-H7PW

D-H7B

D-H7BW

D-H7BA

Wiring style

Three wire type

Two wire type

Output style

NPN type

PNP type

––

Application

IC, Relay, PLC

24V DC Relay, PLC

Source voltage

DC5·12·24V (DC4.5~28V)

––

Current consumption

10mA or less

––

Load voltage

DC28V or less

––

DC24V (DC10~28V)

Load current

40mA or less

80mA or less

5~40mA or less

Internal voltage drop

1.5V or less

0.8V or less

4V or less

Leak current

100µA or less at DC24V

0.8mA or less at DC24V

Operating time

1ms or less

Operating

One colour

Two colour

One colour

Two colour

One colour

Two colour

indicator lamp*
Proof impact

1000m/s

2

Insulation resistance

50M 

or more at DC500V mega

Proof voltage

AC1000V for 1 minute (lead wire, between cases)

Ambient temperature

-10~60°C

Protection structure

IEC529 standard IP67, JISC0920

*  One colour: Red diode lights when ON

Two colour: Operating position······Red diode lights

Optimum operating position······Green diode lights

not start.
Ensure that, if using a load that can generate a surge voltage ie. Relay
or Solenoid valve, a built-in surge protection circuit is installed.

If an auto-switch is to be used to generate an inter-lock signal, which
requires high reliability, then instigate mechanical protection, or place
another switch, double inter-lock style, together. Ensure the correct
operation of this Inter-lock frequently.

Ensure, when installing this product, that enough space is
available for maintenance to be carried out.

CAUTION

Do not subject this product to

any

form of impact damage.

Do not lift an actuator, fitted with an auto-switch, by the switch lead,
as stress may be applied to the inside of the switch.
Ensure auto-switch mounting screw is tightened to the correct torque
(see Mounting of switch bracket).
Adjust the auto-switch so that the ON position coincides with the cen-
tre of the operating area. If the switch is set to one side or the other
of this centre position then inconsistent operation will occur.

Wiring

Do not apply repeated bending or tensile forces to the 
connecting wiring as this may cause disconnection. Bend radius is
approximately R40mm or more.
Connect the load before applying power to the switch, failure to do so
may cause excess current to damage the switch.
Ensure wiring is carried out correctly. Not all wiring modes have pro-
tection and the switch may be damaged.
Separate signal lines from power/high voltage lines to prevent 'noise'.
Ensure all wiring is correctly and fully insulated.

WARNING

DO NOT USE THIS SWITCH IN AN EXPLOSIVE ATMOSPHERE.
Do not use this switch in high magnetic fields, as this will damage the
switch and actuator magnet.
Do not use this switch in water-laden atmospheres, oil or chemical
laden atmospheres.

Do not use this switch in conditions where temperatures are outside
of the switch operating Spec.
Protect the switch from weld spatter and accumulation of iron dust etc.

Maintenance

To avoid incorrect operation periodic maintenance should be carried out.

Check tightness of mounting screw regularly to prevent possible
movement of the switch from its set position.

Regularly check condition of the wiring. Repair insulation damage
immediately or replace the switch.

If a red LED is showing this indicates that the switch has moved
from the set position. Re-adjust the switch until the green LED is
showing (this is the optimum position).

CAUTION

If detection failure occurs i.e. LED remains ON follow the faultfinding
chart above (Fig 1).

For applications involving contact with water, elasticity, and welding,
contact your nearest SMC Office.

(See at the end of this Manual.)

If the hysteresis, between the ON and OFF position of the switch is
incorrect please consult SMC.

Exterior dimensions

Basic wiring (Fig 4)

Lead wire colour in brackets indicates products complying with IEC.

Connection with PLC (sequence controller)

Depending on the PLC input specification, the output design of 3 wire
type switches and 2 wire type switches differ. (See below)

PLC input specification

3 wire output type

2 wire connecting type

Sink input

NPN output

Sink output mode

Source input

PNP output

Source output mode

Mounting of switch bracket

Each actuator has a specified mounting bracket to mount the switch
to the actuator. The type of bracket depends on the following:

Type of actuator, and tube O.D. Please consult the current 
actuator catalogue for details.

When fitting an auto-switch for the first time please ensure that the
actuator is fitted with a magnet and that the brackets are correct for
the actuator type.

Appropriate tightening torque

M3 mounting screw correct tightening torque is 0.8~1.0 Nm
(8.2~10.2 kgf.cm)

S

Setting the switch detection position

Position the actuator at its stroke end.

Single colour display

Move the auto-switch into the centre of the operating range and
ensure that the red LED is ON.

Two colour display

Move the Auto-switch into the centre of the operating range and
ensure that the green LED is ON.

Detecting actuator stroke end

Refer to dimensions A & B in the actuator catalogue.

CAUTION

D-H7BA (Improved water resistant type)

Although this switch has improved properties with regard to oil and
water resistance, it should not be exposed to cutting oil, which con-
tains additives, high-pressure water jets or extremes of temperature.

CAUTION

In all cases do not clean with a solvent solution.

017A/ENG

D-#S-TFI95GB

When you enquire about the product, please contact the following 

SMC Corporation

:

ENGLAND

Phone 01908-563888

TURKEY

Phone 212-2211512

ITALY

Phone 02-92711

GERMANY

Phone 6103-402-0

HOLLAND

Phone 020-5318888

FRANCE

Phone 01-64-76-10-00

SWITZERLAND

Phone 052-34-0022

SWEDEN

Phone 08-603 07 00

SPAIN

Phone 945-184100

AUSTRIA

Phone 02262-62-280

Phone 902-255255

IRELAND

Phone 01-4501822

GREECE

Phone 01-3426076

DENMARK

Phone 8738-0800

FINLAND

Phone 09-68 10 21

NORWAY

Phone 67-12 90 20

BELGIUM

Phone 03-3551464

POLAND

Phone 48-22-6131847

Installation

Actuators

WARNING

To eliminate the possibility of magnetic interference between switch-
es, please ensure that, when two or more actuators are used, in 
parallel, they are kept at least 40mm apart.

Mid-stoke position sensing

Exercise caution when attempting to detect the piston at mid-position,
without stopping, as the switch detection time may be too short,
particularly at relatively high actuator speeds. Detectable max. piston
speed can be obtained by the following formula:

V (mm/s) =   Auto switch operating range (mm)      

Load operating time (m/s)

Where possible keep all wiring as short as possible.

CAUTION

If the 2-wire type solid state auto-switch has a large internal voltage
drop, and leakage current is also high, it is possible that the load may
not operate correctly due to incorrect load spec. Please confirm the fol-

lowing conditions before operation, and note that the internal voltage
drop and leak current have a considerable influence on the serial and
parallel connection of the 2-wire solid state switch.

Leak current influence

I.E Voltage generated to the load when the power is turned off.

Voltage generated = Auto-switch leak current x load resistance. If this
voltage exceeds the OFF voltage of the load, it is possible that the load
may stay ON. In order to match the condition of the controller-input
unit and leak current, then auto-switch leak current must be less than
input unit OFF current.

Internal voltage drop

Should an internal voltage drop occur, then the load supply voltage
will also drop as the switch operates. (Load supply voltage = Source
voltage – Internal voltage drop).
When the load supply voltage becomes lower than the switch ON 
voltage, the load may not operate correctly.

WARNING

Incorrect load voltage

Although the switch will operate correctly, even if the load current is
below the limit of the specification, the indicator light will be
'dimmed'. If the load current falls to 3mA, or lower, the operation may

Fig 1

Fig 2

Fig 3

Fig 4

Load spec. check

1

 . . .ON voltage > Load voltage - Internal voltage drop

Load spec. check 

2

 . . .OFF current  > Leak current

 . . .Switch output parts failure (replace)

 . . .Correct wiring

 . . .Replace switch 2 wires 

3 wires

 . . . .Switch failure

 . . . .Replace cylinder. Detectable magnet field inadequate (No magnet)

 . . . .Replace PLC input board or replace switch 2 wire 

R

3 wires

Fig 5

Fig 6

D-H7A1/H7A2/H7B

D-H7BW/H7NW/H7PW/H7BA

Autoswitch set screw

M3X0. 5x14

l

Autoswitch

Autoswitch mounting band

(with bracket)

Problem

Condition

Indicator 

lamp lights

2 wires/

3 wires

Source voltage
or load voltage

Stay OFF

(sometimes ON)

Normal

3 wires

Normal

Normal

Normal

Normal

Abnormal

Abnormal

Abnormal

Abnormal

Stay OFF

Stay OFF

Indicator 

lamp lights

Load spec.

check

1

Load spec.

check 

2

Replace the

switch

2 wires/

3 wires

Stay ON 

(sometimes OFF)

Normal

2 wires

Normal

Stay ON

Wiring

(output) check

A

A

A

A

A

B

B

B

B

C

C

D

D

D

E

E

F

F

Piston moving
direction

Piston moving
direction

ON position

Hysteresis

Hysteresis

OFF position

29

9

ø3. 5

10. 5

4. 3

4. 6

8

8

11.

5

ø3.

4

6.

5

29

9

ø3. 5

4. 3

4. 6

8

8

11.

5

ø3.

4

6.

5

Most sensitive position

Indicator lamp

Indicator lamp

ON

OFF

Red

Red

Green

Operating range

3 wire type NPN output

2 wire type (Sink output)

2 wire type (Source output)

3 wire type PNP output

Switch

Load

Brown (Red)

OUT

Black (White)

DC(-)

DC(+)

Blue (Black)

Power
source

Switch

Load

Brown (Red)

OUT(-)

OUT(+)

Blue (Black)

Power
source

Switch

Load

Brown (Red)

OUT(-)

OUT(+)

Power
source

Switch

Load

Brown (Red)

OUT

Black (White)

DC(-)

DC(+)

Blue (Black)

Blue (Black)

Power
source

3 wires

2 wires

Abnormal

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