LITTELFUSE REED SWITCH SELECTION GUIDE
A quick reference guide to selecting reed switches for electronic applications
MITI-3V1
MDSR-10
MDSR-7
FLEX-14
MDCG-4
MACD-14
HA15-2
MLRR-4
MLRR-3
This compact reed switch is
somewhat more expensive
than larger parts. It is typically
used only when minimizing
component size is critical.
This switch is also available in
surface-mount* packaging as
the MISM-3V1R (Tape & Reel)
and MISM-3V1B (Bulk Pack).
This cost-effective, small
reed switch is also available in
surface-mount* packaging as
the MDSM-10R (Tape & Reel),
the MDSM-10B (Bulk Pack),
and the 59170 (overmolded*).
This small reed switch is only
slightly larger than the MITI-7
and MDSR-10 switches, but
with the same small glass
diameter as those switches.
The MDSR-7 switch is also
available in an overmolded*
PCB-mount package, including
surface-mount* packaging, as
the 59165 and 59045.
The FLEX-14’s leads are easily
formed or bent to meet an
application’s requirements.
In addition, its slightly shorter
glass length and slightly
longer lead length provide high
flexibility when designing it
into products.
The MDCG-4 is one of
Littelfuse most popular reed
switches and is available in
a wide range of sensitivities.
It is also available in an
overmolded* PCB-mount
package as the 59050, and in
surface-mount* packaging as
the MDSM-4R (Tape & Reel)
and MDSM-4B (Bulk Pack).
The MACD-14 has low
hysteresis between activate
(closure) and deactivate
(opening). This is also known
as close differential. This
feature can be an advantage
in some sensing applications.
One such example is when
the activating magnet travel
distance is limited. It is also
available in surface-mount*
packaging as the MASM-14R
(Tape & Reel) and MASM-14B
(Bulk Pack).
The HA15-2 is physically very
similar to the MDCG-4, but it
uses a pressurized nitrogen
atmosphere that allows
switching 240 Vac power line
mains voltages. The HA15-2
also provides good switching
life on non-suppressed
inductive loads, as well as less
demanding ones. It is available
in a wide variety of Littelfuse
sensor packages.
The MLRR-4 has the smallest
hysteresis between activate
and deactivate (close
differential). This can be an
advantage in some sensing
applications, but it can also
be a disadvantage in sensing
applications where the magnet
is moving slowly. The MLRR-4
is well suited to switching
small incandescent lamps (< 28
V, < 0.2 A). This switch is also
available in surface-mount*
packaging as the MLSM-4R
(Tape & Reel) and MLSM-4B
(Bulk Pack).
This reed switch has the
longest wire leads of any of
the 15.24 mm / 0.600 inch glass
length switches. The MLRR-3
is a cost-effective, small 20
Watt switch. It provides good
switching life on a wide range
of loads. It is also available in
surface-mount* packaging as
the MLSM-3R (Tape & Reel) and
MLSM-3B (Bulk Pack).
*See other side for product image and specifications.
MARR-5
MRPR-20
MDRR-DT
DRR-129
DRR-DTH and DRT-DTH
The MARR-5 has advantages in high voltage and low temperature applications
because its electrical contacts are in a vacuum instead of a nitrogen atmosphere.
The voltage ratings are 1000 Vdc switching and 2000 Vdc breakdown (see data sheet
for additional information). The switch is rated at a rather high 35 AT (Ampere-turn)
in order to meet the 1000 Vdc switching voltage at low currents (< 10 mA). If a higher
switching current or RC arc suppression is used, it’s possible to realize a higher
switching voltage or lower switch AT value. Contact Littelfuse for recommendations.
As the switch AT increases (sensitivity decreases), the contact gap increases,
resulting in increased voltage capability. Typical breakdown voltage is 100 times the
AT value. In addition, the MARR-5 can be used at temperatures near absolute zero
if carefully packaged. For additional information, see Littelfuse Application Note
AN105 – Extreme Temperature Reed Switch Operation.
NOTE:
The MRPR-20 uses a pressurized nitrogen
atmosphere that allows switching up to 265 Vac and
50 VA. This switch maintains a 750 Vdc breakdown
across the sensitivity range of 17 AT to 43 AT. The
MRPR-20 has good switching life capability for a
variety of electrical loads from Vdc logic level to 240
Vac power line mains voltage.
This is a single-pole, double-throw (SPDT) reed
switch, also known as a Form C reed switch.
The addition of a normally closed contact to the
standard normally open contact meets the needs of
a wide variety of applications. It is not unusual for
the normally closed contact to be the only contact
used in an application. However, this capability
results in compromises that affect the switching
voltage and current, as well as cost.
The DRR-129 can offer the highest electrical
contact ratings of any of Littelfuse reed switches
because of its large wire diameter and large contact
gap. However, these characteristics can also
represent disadvantages in terms of size, cost, and
low magnetic sensitivity. For some applications,
however, the DRR-129’s 100 W, 400 V, 3 A switching
capability can be essential.
Like the MDRR-DT, the DRR-DTH and DRT-DTH
are single-pole, double-throw (SPDT) reed
switches. Their large size provides higher electrical
performance but also increases their cost. The
DRR-DTH uses a contact coating similar to many
of Littelfuse reed switches. The DRT-DTH uses
a tungsten contact coating that is very good on
heavy loads; however, it tends to increase contact
resistance when switching light loads such as <
0.25 A, < 6 V.
Market Segments / Applications:
Reed switches are used in a number of market applications including, but not limited to:
• White goods and small home appliances, such as fluid level and position sensors
• Gas and water metering such as tamper switch and pulse counting
• Safety and security, such as electronic door locks, window/door sensors, and
smoke alarms
• Others, such as fitness equipment, electronic shelf labeling, solar trackers, and
equipment for hazardous environments
Visit us at
littelfuse.com
for assistance with application solutions.
This tool should ONLY be used as a quick reference guide to suggest a starting point in the selection
process. Once a part has been selected, the designer should retrieve the actual datasheet from
Littelfuse.com.
Littelfuse always recommends conducting application testing to verify the correct part selection.
In order to use this quick reference guide, the designer has to know just a few of key parameters,
such as switching power, voltage, current, size, mounting method, and safety certifications.
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