| Lead Forming (cutting and bending) |
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- When cutting or bending external leads extreme caution should be exercised
not to exert any undue stress that can result in damage or deterioration of the
glass-to-metal seal. Proper clamping is necessary (see Fig. 1)
- Recommended distance, from end of glass capsule, for lead bending and
cutting (dimension "1" on Fig. 1) are 3 mm minimum for miniature reed
switches (glass length 9 to 20 mm) and 8 mm minimum for large reed switches
(glass length of 30 mm and more).
- As a result of cutting external leads, Pull-In and Drop-Out AT (Ampere
Turns) will increase. Take this into consideration during design (see Fig. 2). Similarly,
bending of external leads will increase Ampere Turns
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| Mounting (soldering and welding) |
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- Excessive high temperature and exposure time may cause damage of the
glass-to-metal seal (crack, leakage, etc.). Quick and reliable soldering
techniques (procedures) need to be applied.
Recommended soldering conditions
are : 280 to 300 deg. C for hand soldering, and 250 to 300 deg. C for wave
soldering.
- When welding reed switch leads, the electromagnetic field generated by the
welding current can operate the switch, that in turn may cause contact damage.
Special
precautions should be used during welding, regarding welding voltage, current
and timing.
Never weld both leads of reed switch at the same time.
- When mounting on a printed circuit board (pcb) attention should be given to
pcb warpage and thermal expansion characteristics. Stress caused by these
factors may also damage the glass-to-metal seal.
When mounting a reed switch
on a pcb, it is recommended to form the leads and provide adequate spacing
between the pcb and the reed switch, or to drop the reed switch into an opening
(cutout) in the pcb (see Fig. 3).
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| Shock and Vibration |
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- When a reed switch is dropped onto a hard surface (floor) from more than
30 cm height, electrical characteristics (Pull-In, Drop-Out, etc.) shall be
altered.
After a reed switch has been dropped and before use in the actual
application, make sure that its characteristics are still within acceptable
limits.
The same is applicable after applying pulling or twisting stress
forces to the reed switch.
- Do not use reed switches above their specified resonant frequencies.
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| Reed Switch Protection |
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- Inductive Loads:
When using reed switches for inductive loads such as
motors, relay coil, solenoids, etc., the contacts will be subjected to high
induced voltages during opening of the contacts (load circuit).
Such high
induced voltages (transients) may cause damage to the reed switch or
significantly reduce its life.
Therefore, protective circuits such as : RC
(snubber), varistors or clamping diodes, are recommended (see Fig. 4).
- Capacitive Loads:
When using reed switches for capacitive loads such as
capacitors, incandescent lamps or long cables (harnesses), the contacts will be
subjected to high surge (inrush) current. Therefore, protective circuits such as
: surge suppressors or current limiting resistors, are recommended (see Fig. 5).
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| External Magnetic Interference |
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- When reed switch and its actuating magnet or coil are located near sources
of strong magnetic interference such as steel plates, transformers, etc., the
reed switch operational characteristics will be altered and false operation is
likely.
Specific cases may be very different from one another, and therefore
sources of possible interference (interaction) should be investigated in a given
application.
- When using multiple reed switches in close proximity to one another,
similar magnetic interference may cause changes of characteristics and false
operation.
If such interference is observed, the reed switches should be
spaced more than 15 mm from one another.
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16475
Canyon Hills Road #3