Detect End Limit Position On Hospital Beds And Mobility - Digi-Key

Detect End Limit Position On Hospital Beds And Mobility
Equipment Using Reed Sensors
REED RELAYS REED SENSORS REED SWITCHES
Introduction
Figure 1. MK14 Sensor physical layout
There are a large number of applications requiring the detection of end limit
position, where electric shock can be a real concern. Hospital beds, for
example, need end position limits when adjusting the bed position. Reed
Sensors are ideal here because they reliably pass very low level voltages and
currents well under any potential power that could cause a shock. Mechanical
limit switches have been used successfully in the past, but can fail prematurely
because they need a higher level of power to operate properly. Mechanical
sensors exposed to the environment will develop films on the contacts. To
break through these films higher switching voltages may be necessary. These
higher voltages are not ideal in a hospital bed environment. Now designers
have turned to the Reed Sensor which uses hermetically sealed reed switches,
which are ideal for switching low signal levels reliably.
Features
• The reed switch used in the Reed Sensor is
hermetically sealed and is therefore not sensitive
to spillage or wet environments
• The hermetically sealed reed switch is ideally
suited for switching low signal level voltages and
currents
• Magnet and Reed Sensor are isolated and
have no physical contact by typically having the
magnet mounted to the movement and the Reed
Sensor mounted and positioned to pick on the
end limit position/s
• The magnet is not affected by its environment
Figure 2. Sensor is mounted to each end position. When the piston reaches its top end
limit position, the magnet actuates the sensor and sounds an alarm.
• Millions of reliable operations
• Cylindrical hole and screw fastening mounting
• Contacts dynamically tested
• Large sensing distances possible
Applications
• Ideal for sensing end position(s)
• Ideal for applications sensing any kind of end
movement even in dirty or wet environments
• Medical mobility equipment
• Hospital beds
• Lift chair position
• Mobility scooter
• Patient lift
• Power wheelchair
• Stair lift position
• Wheelchair ramp position
Figure 3. Sensor is mounted to each end position. When the piston reaches its bottom
end limit position, the magnet actuates the sensor and sounds an alarm.
Reed Sensors Are Ideal for Sensing End Position On Hospital
Beds And Other Mobility Equipment
Hospital beds, motorized chairs, special lifts for bath tubs, massage chairs, etc.
all require end position detection. Since these are used by the consumer, care
needs to be taken to use low power switching devices eliminating the threat of
electrical shock to the user. Also, dust, dirt, and moisture may be present with
the potential for spillage occurring, all of which, could create faulty operation of
switching devices.
MEDER electronic
Application
MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: info@meder.com
MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: salesusa@meder.com
Page 1 of 3
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Detect End Limit Position On Hospital Beds And Mobility
Equipment Using Reed Sensors
REED RELAYS REED SENSORS REED SWITCHES
Specifications
Operate specs
Min Max Units
Must close distance
5
25
mm
Must open distance
5
25
mm
Hysteresis
Load Characteristics
Switching voltage
Switching current
Carry current
Contact rating
Static Contact
resistance
Dynamic contact
resistance
Breakdown voltage
Operate time
Release time
Operate Temp
Storage Temp
Mechanical limit switches have been used in the past, but can fail prematurely,
because they require higher switching power to operate properly. Designers
have tried to operate them with lower power, have found they are not very
reliable. Increasing the power level would result in the threat of electrical shock.
Designers have not turned the MEDER’s reed sensors solving both of the
above issues. The reed sensor uses hermetically sealed reed switches which
are ideal for switch low power signals eliminating the potential for electric shock.
And since the reed switches are hermetically sealed and packaged in strong
high strength plastic, they are virtually fault free in any environment.
Typical 50%
Min Max Units
200
0.5
1.5
10
150
200
320
0.5
0.1
-20 85
-20 85
V
Amps
Amps
Watts
mΩ
mΩ
V
msec
msec
°C
°C
In these requirements the magnet is usually mounted to the movement
mechanism and the reed sensor is mounted at the end position detection point.
When the mechanism and magnet are moved and approach the reed sensor
the reed contacts will close sending a signal to the electronics, which in turn
halts the motion. In this way reliable operation is achieved.
It is also easily accomplished to sense several positions in a given motion and
not only the end movement. Reed sensors can be strategically placed at all
interested sensing points to carry out this operation. Also multiple magnets can
be used to accomplish a similar task. If the motion is very complex,
combinations of reed sensors and magnets may be used effectively to
accomplish the given detection.
MEDER’s reed sensors are available in several packages with various
connector or lead options allowing the users to meet exact design details. The
magnets can also be packaged in an assortment of ways as well. Because of
the multitude of design requirements, MEDER, in a matter of fact manner, has
the capability of developing specialized packaging for both the reed sensor and
the magnet to meet the user’s specific needs.
Consider some of the below options in cylindrical and rectangular versions for
end limit sensor or other similar applications.
Cylindrical Panel Mount Series
Series
MK03
MK03
Dimensions
mm
Dia
5.25
L
25.5
Illustration
inches
0.207
1.004
MK14
MK14
Dia
L
4
25.5
0.157
1.004
MK18
MK18
Dia
L
5
17
0.197
0.669
MK20/1
MK20/1
Dia
L
2.72
10
0.107
0.394
MEDER electronic
Application
MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: info@meder.com
MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: salesusa@meder.com
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Detect End Limit Position On Hospital Beds And Mobility
Equipment Using Reed Sensors
REED RELAYS REED SENSORS REED SWITCHES
Rectangular Screw Flange Mount Series
Series
MK04
MK05
MK05
MK12
MK12
Dimensions
mm
W
13.9
H
5.9
L
23.0
W
19.6
H
6.1
L
23.2
W
H
L
14.9
6.9
32.0
Illustration
inches
0.547
0.232
0.906
0.772
0.240
0.913
0.587
0.272
1.260
**Consult
the factory for more options not listed above.
**
MEDER electronic
Application
MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: info@meder.com
MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: salesusa@meder.com
Page 3 of 3
www.meder.com