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 magnetoresistive sensor 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 diodefor 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
BlueCoil
Black0 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 +Vblue 0V
Load+V black
brown +V
blue Load 0V
QM/33
QM/33/C
QM/34/P
QM/34/N
QM/34/S
brown +Vblue 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 +Vblue 0V
blackpnp
Load 0V
13
4pnp
brown +Vblue 0V
black Load 0V
1
brown +V
blacknpn
Load +V
blue 0V
3
4npn
brown +V
black Load +V
blue 0V
black Load 0V
brown +Vblue 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
0V0VLoad
Load
+V
M/40
M/40/P
M/40/C
brown
blue Load 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 +Vblue 0V
blackpnp
Load 0V
brown +V
blacknpn
Load +V
blue 0V
M/41
M/42
13
4pnp
brown +Vblue 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 mmSwitching frequency 500
to 2000 HzWith 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
+V
brown
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 reset hysteresis
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