Switches and Sensors

For integrated control systems

Contents

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� Magnetic cylinders

� Reed switch principle

� Sensor principle

� QM/45/* range

� QM/33,34,134 range

� M/40,41,42 range

� Inductive proximity sensors

� Vacuum electric switch

� Vacuum electronic switch

� Cable capacitance� Introduction

Introduction

� Typical electro-pneumatic systems consist of:

� magnetic cylinders and solenoid valves for dynamic power

� reed switches and sensors for feedback

� electronic logic for control

� Reed switches and solid state magnetic sensors are fitted to cylinders to feedback particular positions of the piston

� Solid state proximity sensors can be used to replace limit switches, for detecting the position of mechanisms or other moving parts

� Reed switches and solid state sensors are small, fast, easy to fit and adjust. They simplify installation on to the machine application

Magnetic cylinders

� Magnetic cylinders have a band of magnetic material inset around the circumference of the piston

� The polarity is in parallel with the axis of the cylinder

� The barrel is made of non ferrous material

� By placing reed switches along the outside of the cylinder, signals can be given at the extreme and intermediate positions of stroke

Click the illustration to start and stop animation

Reed switch principle

� A basic reed switch consists of a small glass tube containing soft iron contact reeds normally sprung open

� When a magnetic field is in range the reeds will become magnetic

� The ends will be of opposite polarity and pull themselves together

Click the illustration to start and stop animation

Magnetic sensor principle

� In the presence of a magnetic field the magnetoresistivesensor has a lower resistance. This causes current to be drawn from the base of the transistor turning it on

� The circuit incorporates l.e.d., reverse polarity protection diodes and suppression diode for an inductive load

sensor

N S

load

+V

0V

Reed switches and sensor

� Slim cylindrical housing

� PVC cable in 2 or 5 metre lengths

� Optional very flexible polyurethane cable

� With or without l.e.d. indicator

� Range of four reed switches and one solid state sensor

Reed switches

� Basic reed switch

� Shown connected to a relay or solenoid coil with diode suppression for d.c. application

� 10 to 30V a.c./d.c.

� Maximum switching power 10 W/VA

Brown

Blue

+ V

0 V

Coil

Protection diode

for d.c. only

QM/45/RAP

Reed switches

� Reed switch with l.e.d. indicator

� Three wires emulating p.n.p. sensor

� Current sourced on the black wire to the coil

� Resistor protects l.e.d. from over voltage

Blue

CoilBlack

0 V

Brown + V

0 V

QM/45/LAP

Protection diode

Reed switches

� Reed switch with l.e.d. indicator and two wires only

� Current sourced on the black wire to the coil

� Zener diode provides small voltage drop to turn on l.e.d.

� 10 to 240V a.c./170V d.c. 10 W/VA maximum

� Shown with VDR for suppression a.c. or d.c.

Blue Coil

0 V

Voltage dependant resistor (VDR)

Brown + V

QM/45/LAP

Reed switches

� Reed switch with l.e.d. indicator

� Three wires emulating n.p.n. sensor

� Current sunk on the blue wire from the load to 0V

� Resistor protects l.e.d. from over voltage

Brown

Black Load

Protection diode

+ V

Blue 0 V

+ VQM/45/LAN

Solid state switches

� Solid state magnetically operated p.n.p. output

� Used for applications where vibration levels are unsuitable for reed switches

� Magnetoresistive sensor element

� ‘Sensor on’ l.e.d. indicator

� 10 to 30 V d.c. 200mA maximum

brown

blue

black

pnp

+V

0V

0V

coil

protection diode

QM/45/EAP

Reed switches and sensors

� Neat cylindrical housing with fixed or plug-in cable

� Straight or 90o plug-in connector cables

� Optional: very flexible polyurethane cable or high temperature (150oC) silicon cable

� With or without l.e.d. indicator

� Wide range of reed switches and solid state sensors

Reed switches

� Plain reed switch

� Plain change-over reed switch

� Three wire reed switch with l.e.d., emulating p.n.p. sensor and plug-in cable

� Three wire reed switch with l.e.d., emulating n.p.n. sensor

� Two wire reed switch with l.e.d.

blue

brown +V

Load

0V

brown +V

blue

black

0V

0V Load

Load

brown +V

blue 0V

Load+V black

brown +V

blueLoad

0V

QM/33

QM/33/C

QM/34/P

QM/34/N

QM/34/S

brown +V

blue 0V

Load0V black

Solid state sensors

� Output p.n.p. fixed cable

� Output p.n.p. plug-in cable

� Output n.p.n. fixed cable

� Output n.p.n. plug-in cable

� Pulse stretcher. Output p.n.p. fixed cable. When operated and released output will remain on for a further 30 ms approximately. Suitable for part stroke position on fast operating cylinders

brown +V

blue 0V

blackpnp

Load 0V

1

3

4pnp

brown +V

blue 0V

black Load 0V

1

brown +V

blacknpn

Load +V

blue 0V

3

4npn

brown +V

black Load +V

blue 0V

blackLoad 0V

brown +V

blue 0V

QM/134

QM/134/P

QM/134/N

QM/134/N/P

QM/134/X

Reed switches and sensors

� Low profile with dove tail slide for cylinders with integral track in extruded body

� Screw tightening

� Fixed cable or plug-in connector cables straight or 90o

� With or without l.e.d.

Reed switches and sensors

� Low profile with dove tail slide for cylinders with integral track in extruded body

� Screw tightening

� Fixed cable or plug-in connector cables straight or 90o

� With or without l.e.d.

Reed switches

� Two wire with l.e.d. 10 to 240V a.c./170V d.c.

� With high temperature cable

� With very flexible polyurethane cable

� Two wire with l.e.d. and plug in cable 10 to 60V a.c./74 d.c.

� Change-over contacts without l.e.d.

+V

blueLoad

0V

brown

brown

blue

black

0V

0VLoad

Load

+V

M/40

M/40/P

M/40/C

brown

blueLoad

0V

+V

TM/40

M/40/*/PU

Solid state magnetic switches

� Output n.p.n. 10 to 30V d.c. 200 mA maximum

� Output p.n.p. 10 to 30V d.c. 200 mA maximum

� Output p.n.p. with very flexible polyurethane cable

� Output p.n.p. with plug-in cable

brown +V

blue 0V

blackpnp

Load 0V

brown +V

blacknpn

Load +V

blue 0V

M/41

M/42

1

3

4pnp

brown +V

blue 0V

black Load 0V

M/42/*/PU

M/42/P

Inductive proximity sensors

� Sense the presence of metal near the tip

� Used as a limit switch for mechanical parts

� Depending on type:

� Range 0.8 to 2 mm

� Switching frequency 500 to 2000 Hz

� With or without l.e.d.

� 10 to 30 or 6 to 30 V d.c.

� Normally closed or normally open p.n.p. output

brown

blue

black

pnp

Load 0V

+Vbrown

blue

black

pnp

Load 0V

+V

M/P28473

M/P70104/1&2

M/P70104/3&4

M/P70104/5&6

M/P70104/7&8

M/P70104/9

Cable capacitance

� Long leads above the standard cable length become a long thin capacitor (equivalent circuit )

� Closing the switch shorts the capacitor, the instant high current overloads and damages the switch contacts

� Fit an inductor (470µH) close to the switch. This damps the surge but has a low steady state resistance

L + V

0 VLoad

+ V

0 V

+ V

0 V

Extended leadsStandard leads

470µH

Vacuum electric switch

� Switches contacts at a vacuum set point

� Adjustable between zero and 0.8 bar absolute

� Normally open and normally closed versions

� Up to 250V a.c./d.c. 2A max

� Repeatability + or - 0.1 bar

� Reset differential 0.2 bar

Vacuum solid state switch

� Analogue output 1 to 5 V proportional to vacuum

� Solid state switched output at vacuum set point

� Adjustable resethysteresis

� Adjustable from zero to 1bar absolute

� Output n.p.n. or p.n.p.vesions

+V dc supply (brown)Analog out (white)

Switch out (black)0 V (blue)

Load

+V dc supply (brown)Analog out (white)Switch out (black)0 V (blue)

Load

U

U

set pointhysteresis

End