AUTOMOTIVE POWER RELAY
USER’S MANUALEM Devices Corporationwww.em-devices.com/en/

Jan, 2024 ERCP23-036-03E

【Safety precautions】
The possibility of defect cannot be eliminated entirely even though EM Devices Corporation has been
making continuous effort to enhance the reliability of the relay. To minimize the risks of damage or
injury to persons of property arising from a defect in the relay, customer must incorporate sufficient
safety measures in its design; such as redundancy, fire-containment and anti-failure features. For properuse of the relay, please check your product with actual load and actual application under actual operating
conditions.
【General】
1. Usage and Storage conditions(1) Ambient temperature
When the relay is used at an ambient temperature exceeding or below the range that is shownin the datasheet and catalog, the performance of the relay may be degraded and the life may
be extremely shortened.
(2) Humidity
Under a high humidity (RH85% or higher) environment for a long time, moisture may
penetrate inside the relay. This moisture may combine with NOx or SOx generated by glow
discharges to produce nitric acid or sulfuric acid. In this case, the acid produced may corrode
the metal that forms the relay, and it may cause operation troubles in the relay.
(3) Low temperature and humidity atmosphere
If the relay is exposed to a low-temperature, low-humidity atmosphere for a long time, its plastic parts may
become brittle and fragile.
(4) Water condensation
Water condensation occurs when the ambient temperature drops suddenly from a high temperature andhumidity, or the relay is suddenly transferred from a low ambient temperature to a high temperature andhumidity. Condensation causes the failures like insulation deterioration, wire disconnection and rust etc.
Please evaluate in the actual usage.
(5) Freezing
Freezing means, the moisture contained in the surrounding environment and inside the relay
freezes when the ambient temperature falls below the freezing point.
The freezing causes the sticking of movable portion, the operation delay and the contact
conduction failure etc. Please evaluate in the actual usage.
(6) Atmospheric pressure
The relay supposes to use under normal pressures (810 to 1200hPa). However, if it is used under other pressure conditions, it’s performance may be destroyed and the relay may be
deformed. This can cause functional troubles with the relays. Be sure to use the relay undernormal pressure conditions.
(7) Vibration and ShockThe use of the relay under conditions that are not specified may cause malfunction or damage.
Excessive vibration and shock during contact load current carrying may cause considerable
damage or wear of the contacts.
Please absolutely avoid the ultrasonic and high frequency vibration to the relay that adversely
affects its performance.

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(8) Influence of magnetic fields
Under the influence of magnetic flux leaking from a transformer, speaker, or magnet placed near the relay;
the operate and release voltage; operate and release time, and other dynamic characteristics may change.
In applications where these characteristics changes can cause problems, it is necessary to take measures
such as magnetic shielding.
(9) Plastic molding for relay body
Please do not use this product in such atmosphere where any kind of organic solvent (as benzene, thinnerand alcohol) and the strong alkali (as ammonia and caustic soda) may be adhered to this product.
(10) Storage
Please do not keep under high temperature and humidity.

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2. Contact load
(1) Limitation of load
Never allow the contact load to exceed the maximum ratings; otherwise, the lifetime of the relay will
be dramatically shortened. The lifetime specified in this specification is for certain load conditions,and other factors must be taken into consideration in actual circuits. Therefore, an accurate lifetime
must be measured in the actual circuit.
(2) Minimum load
Use the relay at a voltage and current higher than the minimum load. Otherwise, the contact
resistance will increase and the electrical continuity cannot be detected. This is because
stabilization of the contact surface (electrically and mechanically eliminating minute substances
generated on the contact surface) by opening/closing the contacts with the minimum load
probably will not occur.
In addition to the above mentioned, even if the load is within the maximum ratings, note that thecurrent does not drop below the minimum load while carrying.
The inspection current should also be used above the minimum load.
(3) Inrush current
When using the relay with a high current or high capacitance load, an inrush current may cause
contact dislocation or deposition; therefore check the feasibility of use in the actual circuit.
(4) Switching loads
There are two types of load current control by a relay. One is “non-working”. It is the load current
that is switched by the transistor, the relay only carries the load current. The other is “working”.
It is a relay that switches and carries the load current. EM Devices recommends the working load
current, because the effect of cleaning contacts by the arc phenomenon at the opening/closing
the contacts will be expected.

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(5) Contact protection circuit
To improve the use of the relay, provide a circuit that suppresses transient current and voltage
applied to contacts during opening and closing. The applicable protection circuit differs
depending on the load type of the contact.
Contact protection effect depends on the location of protection circuit (load side or contact side, thedistance between contact and protection circuit). It is important to confirm the effectiveness of theprotection circuit in the actual circuit. In some cases, it is also necessary to conduct lifetime tests using anappropriate equivalent circuit.
(a) Inductive load
In inductive load, electromotive force is generated when the contacts are open. This
electromotive force generates an electrical discharge such as arcing and glow discharge. This
contact phenomenon can cause extreme contact erosion. To avoid contact erosion, a contact
protection circuit is applied to absorb the electromotive force.
Table 1 shows examples of contact protection circuits. Please do not use the protection circuitsof capacitor only shown in Table 2.

V
Contacts open
E

Inductive load

Figure 1 Inductive load circuit

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Protection element

Table 1 Inductive load contact protection circuit
Circuit example

Inductive load

Capacitor+
Resistor

R

Contact Voltage(V)
0.5 to 1

R(Ω) =C

Remarks

C(μF) = (0.5 to 1) x Contact Current(A)（CR Circuit）

R

The withstand voltage of a non-polar
capacitor should be 300V or higher.

Inductive loadC

Varistor

Diode

Diode
+
Zener Diode

Inductive load

High voltage is suppressed by using thevoltage characteristics of the varistor.

Inductive load

Pay attention to the reverse withstandvoltage of the diode. The release time of
the relay or solenoid of the load becomeslong.

Inductive load

The ON time of the diode is controlled byusing the Zener voltage characteristics andthe release time of the relay or solenoid of
the load can be shortened.

Table 2 Example of wrong circuit with a capacitor

C

Load

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This circuit is effective forarc suppression when thecontacts are opened,
but when the contacts
are closed a capacitor
short-circuit current flows,
making the contacts more
susceptible to metal
deposition.

5

C

Load

This circuit is effective forarc suppression when thecontacts are opened,
but when the contacts
are closed a capacitor
charging current flows,
making the contacts more
susceptible to metal
deposition.

Jan, 2024 ERCP23-036-03E

(b) Capacitive load (I)Capacitors are often used in parallel to the loads like motors to prevent noise and other purpose as
shown in figure 2. In that case, inrush current is generated in the circuit. As a result, the contacts canstick together due to projection and pitting that are both formed at contact surface. So, it is necessary to
hold down the inrush current by resistor which is connected in series to capacitor. It is desirable thatcapacitor value is as small as possible and the resistor value is as large as possible.

Load

Figure 2 Inrush current of load from capacitor(c) Capacitive load (II)It is necessary to be careful when capacitors are connected in the circuit as shown in Figure 3.
When the common contact moves from the make contact to the break contact, the motor generates
electromotive force. Capacitor can be charged by over supply voltage. Bigger inrush current from thecapacitor flows to the break contact. Because the break contact has the bounce at ON, inrush current
damages the break contact. Therefore it is necessary to decrease the inrush current by a resistor whichis connected in series to capacitor as shown in Figure 3.
Moreover, a diode connected with the relay coil in parallel can reduce bounces. The diode is more
effective than a Zener diode for it.
Use a resistor to limit
i

R
C

E

M

Inductive loads
such as Motor

Figure 3 Countermeasure against capacitor in inductive load circuit

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(d) Lamp load
Lamp loads like tungsten lamps, have a low initial resistance so that an inrush current of 5 to 10 times ashigh as the steady state current may flow through the relay contacts. In this case, it is necessary to keep
the current within the maximum rated value. A current-limiting resistor is connected to the contacts inseries.
Current limiting resistor
Without current limiting resistor
Current
Contacts

With current limiting resistor

Lamp
E

Time

Figure 4 Inrush current under lamp load(e) Stray line capacitance
When the stray line capacitance is large, the inrush current that is generated due to the stray line
capacitance poses a problem. The electric charge on the line capacitance is discharged directly throughthe contacts when the contacts are closed. The smaller the wiring cable characteristic impedance andthe longer the cable, the greater wear on the contacts. It is necessary to connect a current-limiting
resistor or surge suppresser in series with the contacts as a protection circuit to suppress the inrush
current.
(6) Applied voltage
Note; in case that the voltage that exceeds maximum ratings is applied to contacts, the circuit cannot be
broken even if the contacts are opened.

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3. Driving relays(1) Ambient temperature
When the relay is used at an ambient temperature exceeding or below the range that is shown in the
catalog, the performance of the relay may be degraded and the life may be extremely shortened.
-

Please use the relay at coil rated voltage within the specified temperature range. NOTE: Permissible coilvoltage may be restricted and must be confirmed before the relay is used.
(Refer to (2) in “Maximum applied coil voltage”).
The operating characteristics of the relay change with ambient temperature. Confirm the temperature
condition in the application and confirm the characteristics changes at the technical documents. Figure
5 shows the example of the temperature characteristics.

Figure 5 Temperature characteristics of relay (example: EX2 relay)(2) Maximum applied coil voltage
The maximum applied voltage of the relay coil depends on the ambient temperature and the carrying load
current. The upper limit is decided on the heat resistance of the relay. It mainly depends on thepermissible temperature of the coil wire and the plastic material. When the voltage applies the coilcontinuously, the coil generates the heat corresponding to applied voltage. Then the coil temperature rises
up. The higher the ambient temperature is, the less the margin of the heat resistance temperature of thecoil wire material is. Therefore, it is necessary to restrict the coil voltage at high ambient temperature.
Figure 6 shows the example of permissible applied voltage. The coil temperature is also affected by theload current. Consult EM Devices about the permissible maximum applied voltage in use condition likeambient temperature, carrying load current and carrying duration.

Figure 6 Coil voltage versus temperature derating characteristics (example)

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(3) Driving current waveform
The relay referred in this specification document was designed to drive in direct current circuit. Note thatwhen a rippled DC power source is used, abnormalities such as beat in the coil may occur.
If the waveform of the relay coil drive voltage gradually increases and decreases, the speed of thecontact’s opening/closing gradually decreases too and the relay may not be able to deliver its inherent
performance. The voltage must instantaneously rise and fall as a pulse.
Pulse

Correct

Non-pulse

Incorrect (avoid)

Figure 7 Coil drive waveform(4) Hot start
There is a case that a relay is energized again immediately after it is energized continuously and after deenergized. This phenomenon is called hot start. The relay might not operate at this case. This is because
the increase in the coil resistance due to heat in the relay causes the current to fall even though theapplied voltage remains constant. This problem occurs especially when the operating temperature is highand a voltage which is lower than the rated voltage is applied. confirm first the must operate voltage at thetime of a hot start.
(5) Long continuous energizing of coil
If the coil is energized continuously for a long time, the sum of relay ambient temperature andtemperature increase due to carrying current of contact and coil must be less than the limit of relay
operating temperature range.
Use of the relay at a temperature outside this range may adversely affect insulation or contact
performance.

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(6) Driving circuit
Since the coil of a relay has inductive impedance, an electromotive force is generated when the circuit isopened. This voltage may damage the relay driver IC. In order to suppress this electromotive force, a diodeis connected in parallel to the coil as shown in Figure 8. The release time increases when a diode isconnected with the coil in parallel.
For HX1, EM1, EM1K and EL1 relay, the circuit shown in Figures 8(c) or (d) are recommended. The circuit
shown in Figure 8(b) is not recommended because the relay cannot provide enough performance.

Relay coil

Diode

Diode

Zener
Diode

Zener
Diode

(a)

(b)

(c)

(d)

Figure 8 Driving circuit(7) Opening/Closing frequency
If the contacts open and close frequently with a high current load, repeated electric discharges may cause
contact metal welding or damage to the contact spring. Consult EM Devices when using the relay with highcurrent load with frequent opening and closing of contacts.
(8) Power source capacity
When the same power source is used for the relay drive and the load such as a lamp load. The moment thecontacts are closed, the source voltage may drop if the power source capacity is small. In this case, therelay may be released or an oscillation phenomenon where the relay repeatedly releases and operates
may occur.
Ensure the power source enough capacity to prevent this phenomenon.

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(9) Polarity reversal circuit
Note the operating sequence of 2 relays in case of polarity reversal circuit, is using two single relays or one
twin relay which is called H-bridge circuit (Figure 9(a)). If two relays (A and B) are switched at a time,
contacts are instantaneously applied power supply voltage and inductive voltage by motor. Contacts aredamaged by discharge of excessive voltage. Contact life might decrease by contact welding or contact
material transition. It is necessary to take more than 100ms intervals for on/off timing between driving A
and B relay (Figure 9(b)).

(a)
TrA
TrB

(b)
Figure 9 Polarity reversal circuit and coil drive timing(10) Latching relay-

Apply a voltage to the coil in the polarity specified by the internal connection diagram of the relay.
With a double coil latching type relay, do not apply voltage in a manner that both the set and resetcoils are energized at the same time.

-

A latching relay is driven by a pulsating coil voltage. The pulse width of this drive voltage must be 10ms
or wider. If the pulse is too short, the relay may not operate.

-

A latching relay is factory-set to the reset state for shipment. However, it may be set while beingtransported due to vibration or shock. Make sure that the relay is reset when its application systemstarts operating. When the relay is employed in a portable system, the circuit must be designed sothat the relay is reset at the beginning of operation of the system because the relay may be set by
unexpected vibration or shock.

-

When configuring a self-holding circuit that uses the self-break contacts of the relay, note that the coildrive circuit is disconnected by the self-contacts, causing troubles such as self-oscillation.

(11) Jump Start
Power relay is the product for 12V battery system and does not correspond to 24V “Jump start” testing.

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4. Influence of relay operation on surroundings(1) Electromagnetic noise
Switching the relay coil generates a high electromotive force due to induction. This high voltage might
break the relay driver circuits such as microcontrollers. Add an appropriate absorption element such as
diode to prevent electronic circuits from malfunctioning.
(2) Arc discharge
Connecting/disconnecting a high current at the relay contacts generates an arc discharge. This discharge
may cause electronic circuits such as microcontrollers to malfunction and therefore it is necessary to takeappropriate measures such as electrostatic shields or separation of power supply.
(3) Generation of leakage magnetic flux
Leakage magnetic flux exists slightly in the vicinity of the relay when in the magnetized state. Magnetic
sensors, etc. that are close to the relay may malfunction.

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5. Handling of relays(1) Use of magazine case stoppers
Generally, relays are packaged in a magazine cases for shipment. When some relays are taken out from thecase and space is freed inside the case, be sure to secure the relays in the case with a stopper. If the relays
are not enough secured, vibration during transportation may cause contact problems.
Stopper

Stopper

Push in to secure the relays

Figure 10 Storage in magazine case(2) Drop
Do not use relays that have been dropped. If an individual relay product falls from the work table, etc. ashock of 9800m/s2 or more is applied to the relay and its functions may be destroyed. Even if the shock isapparently weak, confirm that there is no abnormality before using the relay.
(3) Long term storage(a) Contacts
When the relay which has been stored for long term is used, check the electric continuity of it. If thestorage condition (temperature, humidity and atmosphere, etc.) is not good, contact surface might
decay and can result to contact failure.
(b) Terminals
Check the solderability of terminals. The surface of terminal will become oxidized and the solderability
might deteriorate. Moreover; oil, water or solvent, etc. must not splash the terminals.

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6. Mounting(1) Print circuit board
For the printed circuit board on which a relay is mounted, use a board of 1 mm or more in thickness. If theprinted circuit board is not thick enough, it may be subject to warpage which will add tension to the relay.
And if a thermal cycle is applied to the soldered part, cracks may be generated in it. Special care is required
for the relay location, base material and through-hole shape.
Consult EM Devices before using the pad layout other than the layout described in catalog.
(2) Relay mounting positiona) The vibration and shock resistance of a relay are greatly affected by its mounting position. It isparticularly important to select the mounting position to prevent the break contacts from being
momentary open instantaneously due to vibration and shock. The vibration and shock resistance are at aminimum when the direction of vibration and shock applied to the relay matches the operation directionof the armature (movable iron piece) and contacts. Therefore, if it is possible to anticipate the direction ofvibration or shocks, mount the relay so that the direction in which vibration or shocks are applied isperpendicular to the direction of the relay armature operation. Figure 11 shows the direction of relay
armature operation.

EP2/ET2

EP1/ET1

EL1/EM1/EM1K

EU1/EU2

EM1KT/EX1/EX2/HX1/AX1

Figure 11 Direction of armature operationb) The projection on contact point is generated and fallen by arc discharge. If the fulcrum (=hinge
position) of armature is located below the contact point, the projection may fall into the gap of fulcrum
and the relay may not operate normally. Therefore, please do NOT mount to the following direction (refer
to Figure 12) when you consider the PCB layout and relay direction. If you cannot avoid the mounting
direction shown in Figure 12 on the actual usage, please contact EM Devices.

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Gravity

Gravity

EU1 Relay

EU2 Relay

Gravity

Gravity

EX1 Relay

EX2 Relay

Gravity

Gravity

EP1 Relay

EP2 Relay

Gravity

Gravity

ET1 Relay

ET2 Relay
Figure 12-1 Mounting direction to avoid

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Gravity

Gravity

EM1 Relay

EM1K Relay

Gravity

Gravity

EM1KT Relay

EL1 Relay

Gravity

Gravity

HX1 Relay

AX1 Relay

Figure 12-2 Mounting direction to avoid

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(3) Chucking
When a relay is mounted using an automatic machine, note that the application of an excessive external
force to the cover at the time of chucking or insertion of the relay may damage or change thecharacteristics of the cover. The chucking force is approximately 4.9N (500 g) or less.
(4) Temporary securing to printed circuit board
Avoid bending the pins to temporarily secure the relay to the printed circuit board. Bending the pins may
degrade sealability or adversely influence the internal mechanism.
(5) Relay mounting area
When two or more relays are installed close together, there is a possibility of abnormal heat generation
due to mutual interference of heat and failure due to insufficient insulation distance between terminals
outside the relay, so please evaluate under actual operating conditions.
(6) Soldering work
In all power relays, terminals are all pre-soldered with Pb free solder.
(Pb free solder: Sn-3Ag-0.5Cu)(a) Automatic soldering (Flow solder)[Recommended conditions]*Preheating: 100°C max. , 60 seconds max.
*Solder temperature: 260°C max.
*Solder time: 5 to 10 seconds(b) Automatic soldering (Reflow solder)Surface mounting type relay EU1/EU2 and pin in paste reflow type relay are for reflow soldering.
Confirm first the recommended temperature profile to EM Devices.
(c) Manual soldering (by soldering iron)[Recommended conditions]*Solder temperature: 350°C max.
*Solder time: 2 to 3 seconds
After soldering is completed, it is recommended to cool down immediately by airflow.
Avoid immersion in cleaning solution immediately after soldering, as this may cause thermal shock anddamage to the airtightness. Work with the relay and the printed circuit board when they are back to room
temperature.
(7) Cutting terminals
Do not cut the terminals of the relay with a revolving blade or an ultrasonic cutter, because vibration thatis applied to the relay during the cutting may cause the characteristics to change, breaking of the coil wireor sticking of the contacts.

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(8) Cleaning
Avoid immersing the board in cleaning solvent after soldering, otherwise breaking sealability might becaused by thermal shock. After the relay and board returned to room temperature, clean them.
(a) Cleaning solvent
Use of alcohol or water-based cleaning solvents is recommended. Never use thinner or benzene
because these solvents may damage the relay housing.
(b) Ultrasonic cleaning
Avoid ultrasonic cleaning because it may damage driving system, movable contact and spring of relay
due to sympathetic vibration.
(9) Coating
In case that coating agent is applied to printed circuit board to secure anticorrosion and insulation, avoid
adhesion of it to relay due to dipping, etc. Selective coating by covering relay with something to insulate
relay from coating agent is recommended. If application of coating agent to relay is unavoidable, let relay
cool to room temperature after soldering and washing before applying coating agent. When thermosetting
material is used as a coating agent, heat it until being cured completely. Note; Avoid the use of silicone
series coating agent otherwise contact failure may occur.
7. Using SMT Relays(1) Printed circuit board
Determine the dimensions of the mounting pads on printed circuit board consider the factor ofsolderability and insulation in order to fit in the mounting accuracy of automatic mounting machine. Referto the dimensions of the mounting pads in the datasheet and catalog.
(2) Reflow solder
The SMT relay is highly resistant to heat. However, solder the relay under the correct temperature
conditions so that the full performance of the relay can function properly. Referring to recommended
temperature profile with EM Devices’ experiment equipment, be sure to confirm the soldering conditions
and the influence of the relay in advance before setting work standards.
(3) Storage
The sealability of a surface mounting relay may be lost if the relay absorbs moisture and when heatedduring soldering. Note this in cleaning and coating process.
8. Others(1) Please do not make additional manufacturing upon the relay housing.

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The information in this document is based on documents issued in November 2023. The information is subject tochange without notice. For actual design-in refer to the latest publications of data sheets, etc., for the most up-dated
specifications of the device.
No part of this document may be copied or reproduced in any form or by any means without the prior written consent of EM Devices Corporation. EM Devices Corporation will not be responsible for any errors which may appear inthis document.
EM Devices Corporation does not assume any liability for infringement of patents, copyrights or other intellectual
property rights of third parties or arising from use of a device described herein or any other liability arising from useof such device. No license, either express, implied; otherwise, it is granted under any patents, copyrights or otherintellectual property rights of EM Devices Corporation or others.
The possibility of defects cannot be eliminated entirely even though EM Devices Corporation has been making
continuous effort to enhance the reliability of miniature power relay. To minimize the risks of damage or injury to persons of property arising from a defect in an EM Devices’ products, customer must incorporate sufficient safety measuresin its design; such as redundancy fire-containment and anti-failure features.
EM Devices products are classified into three quality grades: Standard, Special, and Specific.
The Specific quality grade applies only to devices that are developed based on a customer designated Quality Assurance
program for a specific application. The recommended applications of a device depend on its quality grade, as indicatedbelow. Customers must check the quality grade for each device before using it in a particular application.
Standard: Computers, office equipment, communications equipment, test and measurement equipment, audio andvisual equipment, home electronic appliances, machine tools, personal electronic equipment andindustrial robots
Special: Transportation equipment (automobiles, trains, ships, etc.), traffic control system, anti-disaster systems,
anti-crime systems, safety equipment and medical equipment (not specifically designed for life sup- port)
Specific: Aircrafts, aerospace equipment, submersible repeaters, nuclear reactor control systems, life support
systems or medical equipment for life support, etc.
The quality grade of EM Devices products is considered as Standard, unless otherwise it is specified in EM De- vices
Datasheets or Data Books. If customers intend to use EM Devices’ products for applications other than those specified
for Standard quality grade, they should contact an EM Devices sales representative in advance.

The quality grade of the products described in this document is considered as Special.

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