REED RELAYS APPLICATION DATA HOW REED RELAYS WORK The term reed relay covers dry reed relays and mercurywetted contact relays, all of which use hermetically sealed reed switches. In both types, the reeds (thin, flat blades) serve multiple functions - as conductor, contacts, springs, and magnetic armatures. Latching switches are manufactured by using a SPST-NO contact, and biasing it with a permanent magnetic that is strong enough to hold the contacts closed, but not strong enough to hold the contact closed when coil power is applied to the coil. The switching process is than reversed by simply reversing the relay coil polarity to close the switch, or by employing a second coil with a reverse field. DRY REED RELAYS MAGNETIC FIELDS Dry reed relays have become an important factor in the relay field. They have the advantage of being hermetically sealed and resistant to atmospheric contamination. They have fast operate and release times and when operated within their rated contact loads, have very long life. A typical dry reed switch capsule is shown in Figure 1. Reed relays in general can be characterized as susceptible to the influences of external magnetic fields. It is important to keep reed relays at a proper distance from each other because of the possibility of magnetic-interaction between them. Proper magnetic shielding must be used to contain stray magnetic fields. When installing reed relays into equipment, one should be aware of the devices within that equipment which can produce magnetic fields. The relays being installed into that equipment should be positioned as far away as possible from any stray magnetic fields and should be shielded to prevent false operations. SUPPORTING TERMINAL GLASS CAPSULE SUPPORTING TERMINAL NORMALLY OPEN CONTACTS Figure 1. Construction of Switch Capsule of Typical Dry Reed switch (SPST-NO) In the basic SPST-NO design, two opposing blades are sealed into a narrow glass capsule and overlapped at their free ends. The contact area is plated typically with rhodium to produce a low contact resistance when contacts are drawn together. The capsule is made of glass and filled with a dry inert gas and then sealed. The capsule is surrounded by an electromagnetic coil. When the coil is energized, the normally open contacts are brought together; when the coil voltage is removed, the blades separate by their own spring tension. Some reeds contain permanent magnets for magnetic biasing to achieve normally closed contacts (SPST-NC) or SPDT contact combinations. The current rating, which is dependent upon the size of the blade and the type and amount of plating, may range from low level to 1 amp. Effective contact protection is essential when switching loads other then dry resistive loads. CONTACT COMBINATIONS. The switches used in dry reed relays provide SPST-NO, SPST-NC, SPDT contact combinations. The SPST-NO corresponds with the basic switch capsule design (Fig.1). The SPST-NC results from a combination of the SPST-NO switch and a permanent magnet strong enough to pull the contacts closed but able to open when coil voltage is applied to the relay coil. In typical true SPDT designs, the armature is mechanically tensioned against the normally closed contact, and is moved to the normally open contact upon application of a magnetic field. The SPDT contact combination can also be achieved by joining a SPST-NO switch with an appropriately adjusted SPST-NC switch, and jumping one side of both switches together to form the movable contact system. Latching contacts, defined as contacts which remain in the position to which they were driven, and stay in that position when coil power is removed from the relay coil. 9/04 6...4 ELECTRICAL CHARACTERISTICS SENSITIVITY: The input power required to operate dry reed relays is determined by the sensitivity of the particular reed switch used, by the number of switches operated by the coil, by the permanent magnet biasing (if used), and the efficiency of the coil and the effectiveness of its coupling to the blades. Minimum input required to effect closure ranges from the very low milliwatt level for a single sensitive capsule to several watts for multipole relays. OPERATE TIME: The coil time constant, overdrive on the coil, and the characteristics of the reed switch determine operate time. With the maximum overdrive voltage applied to the coil, reed relays will operate in approximately the 200 microsecond range. When driven at rated coil voltage, usually the relays will operate at about one millisecond. RELEASE TIME: With the coil unsuppressed, dry reed switch contacts release in a fraction of a millisecond. SPST-NO contacts will open in as little as 50 microseconds. Magnetically biased SPST-NC and SPDT switches reclose from 100 microseconds to 1 millisecond respectively. If the relay coil is suppressed, release times are increased. Diode suppression can delay release times for several milliseconds, depending on coil characteristics, coil voltage, and reed release characteristics. CONTACT BOUNCE Dry reed contacts bounce on closure as with any other hard contact relay.The duration of bounce on a Dry reed switch is typically very short, and is in part dependent on drive level. In some of the faster devices, the sum of the operate time and bounce is relatively constant. As drive is increased, the operate time decreases with bounce time increasing. The normally closed contacts of a SPDT switch bounce more then the normally open contacts. Magnetically biased SPST-NC contacts exhibit essentially the same bounce characteristics as SPST-NO switches. REED RELAYS APPLICATION DATA CONTACT RESISTANCE ENVIRONMENTAL CHARACTERISTICS The reeds (blades) in a dry reed switch are made of magnetic material which has a high volume resistivity, terminal-toterminal resistance is somewhat higher than in some other types of relays. Typical specification limits for initial resistance of a SPST-NO reed relay is 0.200 ohms max (200 milliohms). Reed relays are used in essentially the same environments as other types of relays. Factors influencing their ability to function would be temperature extremes beyond specified limits INSULATION RESISTANCE The reed switch structure, with so few elements free to move, has a better defined response to vibration than other relay types. With vibration inputs reasonably separated from the resonant frequency, the reed relay will withstand relatively high inputs, 20 g's or more. At resonance of the reeds, the typical device can fail at very low input levels. Typical resonance frequency is 2000 hz. A dry reed switch made in a properly controlled internal atmosphere will have an insulation resistance of 1012 to 1013 ohms or greater. When it is assembled into a relay, parallel insulation paths reduce this to typical values of 1013 ohms. Depending on the particular manner of relay construction, exposure to high humidity or contaminating environments can appreciably lower final insulation resistance. CAPACITANCE Reed capsules typically have low terminal-to-terminal capacitance. However, in the typicall relay structure where the switch is surrounded by a coil, capacitance from each reed to the coil act to increase capacitance many times. If the increased capacitance is objectionable, it can be reduced by placing a grounded electrostatic shield between the switch and coil. DIELECTRIC WITHSTAND VOLTAGE With the exception of the High-Voltage dry reed switches (capsules that are pressurized or evacuated), the dielectric strength limitation of relays is determined by the ampere turn sensitivity of the switches used. A typical limit is 200 VAC. The dielectric withstand voltage between switch and coil terminals is typically 500 VAC. VIBRATION SHOCK Dry reed relays will withstand relatively high levels of shock. SPST-NO contacts are usually rated to pass 30 to 50 g's, 11 milliseconds, half sign wave shock, without false operation of contacts. Switches exposed to a magnetic field that keep the contacts in a closed position, such as in the biased latching form, demonstrate somewhat lower resistance to shock. Normally closed contacts of mechanically biased SPDT switches may also fail at lower shock levels. TEMPERATURE Differential expansion or contraction of reed switches and materials used in relay assemblies can lead to fracture of the switches. Reed relays are capable of withstanding temperature cycling or temperature shock over a range of at least -50C to + 100C. These limits should be applied to the application to prevent switch failure. CONTACT PROTECTION THERMAL EMF Since thermally generated voltages result from thermal gradients within the relay assembly, relays built to minimize this effect often use sensitive switches to reduce required coil power, and thermally conductive materials to reduce temperature gradients. Latching relays, which may be operated by a short duration pulse, are often used if the operational rate is not changed for longer periods of time because coil power is not required to keep the relay in the on or off position after the initial turn on or turn off pulse. NOISE Noise is defined as a voltage appearing between terminals of a switch for a few milliseconds following closure of the contacts. It occurs because the reeds (blades) are moving in a magnetic field and because voltages are produced within them by magnetostrictive effects. From an application standpoint, noise is important if the signal switched by the reed is to be used within a few milliseconds immediately following closure of the contacts. When noise is critical in an application, a peak-to-peak limit must be established by measurement techniques, including filters which must be specified for that particular switching application. Tungsten lamp, inductive and capacitive discharge load are extremely detrimental to reed switches and reduce life considerably. Illustrated below are typical suppression circuits which are necessary for maximum contact life. INPUT R INPUT R Figure 3 Initial cold filament turn-on current is often 16 times higher than the rated operating current of the lamp. A current limiting resistor in series with the load, or a bleeder resistor across the contacts will suppress the inrush current. The same circuits can be used with capacitive loads, as shown in Figure 3. INPUT INPUT Figure 4 DC inductive loads call for either a diode or a thyristor to be placed across the load. These circuits are necessary to protect the contacts when inductive loads are to be switched in a circuit, as shown in Figure 4. 9/04 6...5 SIP & DIP MINIATURE REED RELAYS OUTLINE DIMENSIONS 107DIP, 171DIP, 172DIP(SPDT) 117SIP DIMENSIONS SHOWN IN INCHES & (MILLIMETERS) . 14 1 0.290 MAX. (7.36) 0.750 MAX. (19.0) 0.100 TYP. (2.54) 0.750 MAX. (19.0) 0.300 MAX. (7.62) 0.290 MAX. (7.36) 0.275 MAX. (6.98) 0.010 TYP. (0.25) 0.020 TYP. (0.51) PIN NO.1 INDICATOR 0.110 (2.79) 0.260 MAX (6.60) 0.075 TYP. (1.90) 0.400 (10.1) 0.020 TYP. (0.51) 0.150 TYP. (3.81) 0.020 TYP. (0.51) 0.200 TYP. (5.08) 0.600 TYP. (15.2) 0.030 TYP. (0.762) 0.010 TYP. (0.25) 0.140TYP. (3.55) 172DIP (DPDT) 0.600 TYP (15.2) GENER AL SPECIFICATIONS (@ 25 C ) COIL Pull-in Voltage AC (50/60 Hz):< Pull-in Voltage DC:< Dropout Voltage AC (50/60 Hz):> Dropout Voltage DC:> Maximum Voltage: Resistance: Coil Power AC (60 Hz): Coil Power DC: CONTA CONTACTS Contact Material: Contact Rating AC Amperes (AC1): % of nominal Not applicable % of nominal 80 % of nominal Not applicable % of nominal 10 % of nominal 110 % 10 VA Not applicable W 117SIP, 107DIP: 0.050 to 0.288 171DIP: 0.050 to 0.270 172DIP: 0125 to 0.540 VA VA ma RHODIUM 117SIP, 107DIP, 171DIP: 0.5 172 DIP: 0.25 117SIP, 107DIP: 120 171DIP, 172 DIP: 60 0.5 100 117SIP, 107DIP, 171DIP: 10 172 DIP: SPDT 4, DPDT 10 Not applicable Not applicable Not applicable Not applicable Not applicable 10 or 0.05 Watt ms ms 1 1 V rms V rms V rms V rms megohms minimum @VDC 500 150 Not applicable Not applicable 1000 @ 500 gs 20 A Contact Rating AC Voltage: V Contact Rating DC Amperes (DC1): Contact Rating DC Voltage: Contact Rating : A V VA General Purpose Rating (75%-80%): Horse Power (AC): Pilot Duty (60 Hz): VA Rating Make: VA Rating Break: Minimum Recommended Load: TIMING Operate Time: Release Time: DIELECTRIC S TRENGTH Coil to Contacts: Across Open Contacts: Pole to Pole: Contacts to Frame: Insulation Resistance: VIBR ATION RESIS TANCE Functional: PIN NO.1 LOCATION UNITS HP 9/04 6...6 PHONE: (843) 393-5778 FAX: (843) 393-4123 EMAIL: info@magnecraft.com 0.800 MAX. (20.32) 0.400 MAX. (10.16) 0.400 MAX. (10.16) 0.100 TYP. (2.54) 0.600 TYP. (15.2) 0.046 TYP. (1.19) 0.3 0.003 (7.62) 0.082 TYP. (2.09) SHOCK RESIS TANCE Functional: TEMPER ATURE Operating, AC Lower: Operating, AC Upper: Operating, DC Lower: Operating, DC Upper: Storage, Lower: Storage, Upper: LIFE EXPECTANC Y EXPECTANCY Electrical @ Rated Load (AC1): Mechanical @ no Load : MISCELLANEOUS Operating Position: Insulation Material: Enclosure Material: Cover Protection Category: Weight: 0.025 (0.635) 0.125 TYP. (3.17) UNITS gs 50 C C C C C C Not applicable Not applicable -40 +85 -40 +105 operations operations 50,000,000 100,000,000 IP grams Any Glass Thermo set plastic 67 1 SIP & DIP MINIATURE REED RELAYS SPST NO OR NC, DPST NO, 0.5 AMP WIRING DIAGRAM COIL MEASURED @ 25 C STANDARD PART NUMBERS NOMINAL INPUT VOLTAGE NOMINAL RESISTANCE (OHMS) (TOP VIEWED ) NOMINAL POWER (mW) SPST - N. O., 0.5 AMP 117SIP W117SIP-1 W117SIP-3 W117SIP-5 SPST - N. C., 0.5 AMP W117SIP-22 W117SIP-23 W117SIP-24 5 12 24 500 W 1000 W 2000 W 50 144 288 5 12 24 500 W 1200 W 2200 W 50 120 270 SPST - NO 1 50 144 288 50 120 220 1 5 12 24 500 W 1000 W 2000 W 50 144 288 50 144 288 5 12 24 500 W 1000 W 2200 W WHEN SPACING SIP RELAYS, THE RELAYS REQUIRE 1/2 INCH SPACING FROM THE SIDE OF THE ADJACENT RELAYS. 5 12 24 500 W 1200 W 2200 W DPST - N. O., 0.5 AMP W171DIP-21 5 500 W W171DIP-23 12 1000 W W171DIP-24 24 2200 W DPST - N. O. WITH CLAMPING DIODE, 0.5 AMP W171DIP-25 W171DIP-27 W171DIP-28 7 1 50 120 270 50 144 270 5 12 24 500 W 1000 W 2200 W 50 120 270 50 120 270 9 8 14 13 1 2 6 7 1 +2 50 144 270 5- 7 WITH DIODE 9 8 6 7 SPST - NO WITH DIODE 14 13 9 8 14 13 9 8 1 2 6 7 1 +2 6 7 SPST - NC 14 13 9 8 14 1 2 6 7 1 + 2 DPST - NO 50 144 270 3+ SPST - NO SPST - NC W171DIP-12 5 200 W W171DIP-14 12 1200 W W171DIP-15 24 2200 W SPST - N. C. WITH CLAMPING DIODE, 0.5 AMP 171DIP 5- 7 WITH DIODE 13 SPST - N. C., 0.5 AMP W171DIP-17 W171DIP-19 W171DIP-20 3+ 5 SPST - NC SPST - NO W171DIP-2 5 500 W W171DIP-4 12 1200 W W171DIP-5 24 2200 W SPST - N. O. WITH CLAMPING DIODE, 0.5 AMP 3 14 SPST - N. O., 0.5 AMP W171DIP-7 W171DIP-9 W171DIP-10 1 SPST - NO W107DIP-1 5 500 y W107DIP-3 12 1000 W W107DIP-4 24 2000 W SPST - N. O. WITH CLAMPING DIODE, 0.5 AMP W107DIP-5 W107DIP-7 W107DIP-8 7 WITH DIODE SPST - N. O., 0.5 AMP 107DIP 5 SPST - NO SPST - N. O. WITH CLAMPING DIODE, 0.5 AMP W117SIP-6 5 500 W W117SIP-8 12 1000 W W117SIP-10 24 2000 W SPST - N. C. WITH CLAMPING DIODE, 0.5 AMP W117SIP-18 5 500 W W117SIP-25 12 1200 W W117SIP-26 24 2200 W 3 SPST - NC 13 WITH DIODE 9 8 6 7 DPST - NO WITH DIODE 14 13 9 8 14 13 9 8 1 2 6 7 1 +2 6 7 9/04 PHONE: (843) 393-5778 FAX: (843) 393-4123 EMAIL: info@magnecraft.com SEE END OF SECTION 6 FOR CROSS REFERENCE 6...7 DIP MINIATURE REED RELAYS SPDT NO, DPDT, 0.25 AMP WIRING DIAGRAM COIL MEASURED @ 25 C STANDARD PART NUMBERS NOMINAL INPUT VOLTAGE NOMINAL RESISTANCE (OHMS) NOMINAL POWER (mW) SPDT, 0.25 AMP 172DIP 200 W W172DIP-1 5 500 W W172DIP-3 12 2200 W W172DIP-4 24 SPDT WITH CLAMPING DIODE, 0.25 AMP 200 W W172DIP-5 5 500 W W172DIP-7 12 2200 W W172DIP-8 24 125 300 270 125 300 270 125 290 270 125 290 270 SPDT 13 9 8 1 2 6 7 125 144 180 125 144 180 172DIP 13 1 + 2 WITH DIODE 9 8 6 7 14 13 9 8 14 13 9 8 1 2 6 7 1 +2 6 7 14 13 1 2 SPDT 9 6 8 7 DPDT DPDT, 0.25 AMP 46 W W172DIP-17 5 266 W W172DIP-19 12 1066 W W172DIP-20 24 DPDT WITH CLAMPING DIODE, 0.25 AMP 46W W172DIP-21 5 266 W W172DIP-23 12 1066 W W172DIP-24 24 14 SPDTWITH DIODE SPDT SPDT, 0.25 AMP 200 W W172DIP-141 5 1000 W W172DIP-145 12 3200 W W172DIP-146 24 SPDT WITH CLAMPING DIODE, 0.25 AMP 200 W W172DIP-147 5 1000 W W172DIP-149 12 3200 W W172DIP-150 24 SPDT 14 SPDT SPDT, 0.25 AMP 200 W W172DIP-31 5 500 W W172DIP-33 12 2200 W W172DIP-34 24 SPDT WITH CLAMPING DIODE, 0.25 AMP 200 W W172DIP-35 5 500 W W172DIP-37 12 2200 W W172DIP-38 24 (TOP VIEWED ) 13 9 8 1 +2 6 7 DPDT 14 13 9 8 1 2 6 7 WITH DIODE 14 14 WITH DIODE 13 9 8 1 +2 6 7 540 540 540 540 540 540 SEE END OF SECTION 6 FOR CROSS REFERENCE WHEN SPACING DIP RELAYS, THE RELAYS REQUIRE 1/2 INCH SPACING FROM THE SIDE OF THE ADJACENT RELAYS. 9/04 6...8 PHONE: (843) 393-5778 FAX: (843) 393-4123 EMAIL: info@magnecraft.com