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REED
SWITCHES
Technical & Applications Information
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Standard packaging for uncut Reed Switches is a box containing
500 pieces. Standard packaging for SMD Reed Switches is Tape &
Reel. Special trays and/or Tape & Reel are available for some types.
Contact your local Coto Technology Representative with your special
packaging needs. Below is a chart of Tape & Reel dimensions for
standard products.
SWITCH TECHNICAL & APPLICATIONS INFORMATION
REED SWITCH PACKAGING
DIRECTION OF FEED
102MM
4.0"
330MM
13"
13MM
.512
2.72 MM
.107
D
B
D
C
EA
FIGURE 1
A
B
C
D
Fig. 1
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Series A B C D E Std. Qty/Reel
CT05 G1 2.57 10.92 8.00 24.00 2.59 2000
CT05 โJ1โ 2.57 8.64 8.00 16.00 2.59 2000
CT10 A2, G1 2.68 16.90 8.00 32.00 3.30 2000
CT10 G2 3.00 19.80 8.00 32.00 3.12 2000
CT10 G4 3.00 19.80 8.00 32.00 3.12 2000
(Dimensions in Millimeters)
Recommended Pad Layouts for SMD Reed Relay Switches
Model Lead Type Fig. # Dim. A Dim. B Dim. C Dim. D
CT05 G1 1.424/10.76 .242/6.14 .091/2.31 .057/1.45
CT05 โJ1โ 1.330/8.38 .168/4.27 .081/2.06 .057/1.45
CT10 A2 1.666/16.92 .529/13.44 .069/1.74 .050/1.27
CT10 G1 1.692/17.57 .520/13.20 .086/2.18 .041/1.04
CT10 G2 1.822/20.87 .640/16.25 .091/2.31 .057/1.45
CT10 G4 1.822/20.87 .640/16.25 .091/2.31 .057/1.45
(Dimensions in Inches/Millimeters)
08082017
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Dry-Reed Switch:
A dry-reed switch is an assembly containing
ferromagnetic contact blades, hermetically sealed in a glass envelope
and operated by an externally-generated magnetic ๎eld, e.g., that
from an actuating coil.
Operate Value:
๎e ampere turn value at which normally-open
contacts close. Lower value re๎ects higher sensitivity.
Operate Time:
๎e operate time is the time between the instant
of application of a magnetic ๎eld to a dry-reed switch and the instant
of the ๎rst physical closing of this switch. ๎e operate time does not
include bounce time.
Release Value:
๎e ampere turn value at which normally-open
contacts, held closed by a magnetic ๎eld, will reopen as ๎eld strength
is reduced.
Release Time:
๎e release time is the time between the instant
of removal of an applied magnetic ๎eld to a dry-reed switch and the
instant of the ๎rst physical opening of this switch. ๎e release time
does not include bounce time.
Bounce:
Bounce is a momentary opening of a switch after initial
closing, or a momentary closing after initial opening.
Bounce Time:
๎e bounce time is the interval of time between
the instant of initial closing (or opening) and the instant of ๎nal clos-
ing (or opening) of the dry-reed switch.
Dry-Reed Switch Contact Resistance:
๎e dry-reed switch
contact resistance is the resistance of the dry-reed switch under
speci๎ed conditions of measurement.
Saturate Value:
๎e saturate value is de๎ned as the value of the
applied magnetic ๎eld at which the dry-reed switch is una๎ected by
further increase of the applied magnetic ๎eld.
GLOSSARY OF TERMS
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Operate and Release Values
Operate and release values are dependent on the measuring coil, the
rate of energization (0.1 AT/ms), the detection of the operate (closing)
and the release (opening) moment, the position of the measuring
coil relative to the earthโs magnetic ๎eld and on the environmental
conditions.
Operate and Release Times
๎e operate and release times are dependent mostly on the energiza-
tion and de-energization rate. ๎ey are proportional to the R/L time
of the coil. Operate time is inversely proportional to the ratio of ener-
gization to operate value. Release time is proportional to the ratio of
energization to release value.
Bounce Time
๎e bounce time is almost independent of the energization, how-
ever, a high energization gives a somewhat shorter bounce time. ๎e
bounce time is dependent on the current to be switched; above ap-
proximately 100 mA the bounce time is almost zero.
Contact Resistance
๎e contact resistance is dependent on the wire composition, wire
diameter, energization and contact layer. ๎e published contact
resistance is measured with an open contact voltage of 20 mV and
a current through the closed contacts of 10 mA, using the 4-point
method (Kelvin method). Distance between measuring points for all
switch types is 41 mm.
Breakdown Voltage
๎e breakdown voltage depends on the gap between the contact
blades, kind of gas ๎lling, gas pressure, material of the contact layer
and the availability of free electrons in the gas. ๎e ๎rst three items
are set by the design of a particular reed switch. ๎e last item is very
dependent on ambient conditions. ๎erefore minimum values are
given in the published data.
Insulation Resistance
๎e insulation resistance is dependent on the condition of the inside
of the glass envelope and on the environment, e.g. relative humidity,
conducting layers on the outside of the glass envelope.
Life Expectancy
๎e life of a dry-reed switch is in๎uenced by the contact layer, the
mechanical characteristics of the reed switch blade, the load, the load
circuit parameters and the applied magnetic ๎eld. ๎e contact layer
and the blade characteristics are determined by the manufacturer.
Load, load circuit parameters and magnetic ๎eld are determined by
the user. ๎e load should be within the maximum published values.
๎e load circuit parameters (wiring capacitance and inductance),
should be kept as low as possible and the applied magnetic ๎eld must
be stronger than necessary for obtaining the maximum operate value.
Remark:
Due to the in๎uence of the load circuit on contact
resistance and sticking, and also the in๎uence of the applied
magnetic ๎eld and used coil or magnet, life-test information can
only be compared when it is the result of testing under exactly
the same conditions (test equipment).
Coils:
๎e electrical characteristics are measured using either the NARM1
coil or the 10JK coil. Using another coil may change these character-
istics. ๎e measuring method e.g. speed, detection and the position
of the coil with respect to the earthโs magnetic ๎eld may also a๎ect
the characteristics. ๎e de๎nitions of the NARM1 coil and the 10JK
coil are as follows:
10JK Coil: 10000 turns of 47 SWG single enameled copper wire
on an elliptical coil former of 12.5 mm winding length.
NARM 1 Coil: 5000 turns of 46 AWG single enameled copper
wire on an elliptical coil former of 10.4 mm winding length.
REED SWITCH CHARACTERISTICS
SWITCH TECHNICAL & APPLICATIONS INFORMATION
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Operation Using a Coil
Figures 2, 3 and 4 illustrate the various methods of operating the
switch using a coil.
With the method given in Fig. 4, the dry-reed switch and/or perma-
nent magnet can be placed either within or outside the coil.
REED SWITCH OPERATION METHODS
Fig. 3: A dry-reed switch mounted outside a coil
NS
lc
Fig.4: A dry-reed switch biased by a permanent magnet and operated by a coil
N
N
S
S
lc
Fig.2: A dry-reed switch mounted within a coil
NS
lc
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SWITCH TECHNICAL & APPLICATIONS INFORMATION
Operation Using a Permanent Magnet
Permanent magnets are also often used to operate dry-reed switches.
Figures 5, 6, 7 and 8 illustrate the various methods available.
REED SWITCH OPERATION METHODS
Fig. 6: Movement, with the magnetic ๎eld
perpendicular to the dry-reed switch
N
S
X
-Y +Y
OFF OFF
HOLD HOLD
-Y (mm) +Y (mm)
ON
OFF
Fig. 8: Rotational movement with two or more pole
ring magnets
N
N
S
N
N
S
S
SON
OFF
NS
N
S
N
S
N
S
Fig. 5: Movement, with the magnetic ๎eld parallel
to the dry-reed switch
NS
X
-Y +Y
OFF OFF
HOLD
-Y (mm) +Y (mm)
ON
Fig. 7: Rotational movement with a bar shaped
permanent magnet
NS
OFF OFF
HOLD HOLD
ON
0180ยบ
90ยบ
ยบ
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Shielding
Ferromagnetic materials which shunt the magnetic ๎elds may be
used to shield a dry-reed switch (see Fig. 9).
Magnetic Application
๎ere are many applications for dry-reed switches used in combina-
tion with a permanent magnet. Figure 10 shows the relationship
between the Gauss values of a permanent magnet and the AT values
of Coto dry-reed switches in the Philips Standard Coil. It enables the
customer to determine which reed switch AT range can be used in
combination with a speci๎c permanent magnet.
REED SWITCH OPERATION METHODS
Fig. 9: Shielding a magnetically operated switch
NS
ON
SHIELD
OFF
Fig. 10: Relationship between the ๎eld strength of a
permanent magnet and the ampere-turn
values of Coto reed switches in the Philips
Standard Coil
1000 706010 20 30 40 50 9080
Philips Standard Coil (AT)
Permanent
Magnet
Field Strength
(Gauss)
250
200
225
150
175
100
125
50
75
25
0
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SWITCH TECHNICAL & APPLICATIONS INFORMATION
Application Information
Should your application require further information, please consult
your nearest Coto Technology sales o๎ce.
Contact Protection
Unless stated otherwise, the published life-expectancy data is based
on resistive loads. For inductive, capacitive or lamp loads, inrush
current or reverse voltage can a๎ect the life of a reed switch. For a
maximum life-time, contact protection is advised.
Inductive Loads
To reduce the high reverse voltage produced when a reed switch
opens, the following contact protection can be applied:
DC voltage: a diode parallel to the load or
the reed switch (see Fig. 11).
AC voltage: An RC-network parallel to the load or
the reed switch (see Fig. 12).
and
where: C in ฮผF; I in A; R in ฮฉ; U in V.
Capacitive Loads
To reduce the high inrush current when a reed switch closes, a
resistor must be connected in series with the capacitance or the reed
switch.
When wiring a load and reed switch over a long distance, electrostat-
ic capacitance, arising from the cable, can damage the reed switch.
To protect against this capacitance a series surge protector (L) or a
resistor should be connected in series.
Lamp Loads
To reduce the high inrush current when a cold incandescent lamp
has to be switched by a reed switch (closing only), a resistor must be
connected in series with the lamp or parallel to the reed switch.
SWITCHING CONSIDERATIONS
C = 10
I2
R =
U
10 1 +
(50
U)
Fig. 11: DC voltage contact protection
+_
Fig. 12: AC voltage contact protection
~
R
C
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REPRESENTATIVES & DISTRIBUTORS ๎ WORLDWIDE
Coto maintains an active network of distributors and representatives across the globe.
Wherever you are, you know that you can always ๎nd knowledgeable personnel who will
be happy to help you ๎nd that perfect small signal switching solution.
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