Monitoring Vehicle Power Windows Using A Reed Sensor REED RELAYS REED SENSORS REED SWITCHES Introduction Power windows have been improving their performance over the years and now use Reed Sensors to control the motors as they reach their end limits. Also, if an object impedes the window’s progress slowing the window’s progress, this slowdown must be detected, particularly when going in the closing position. This is particularly important if one’s arm or hand is between the top of the window and door. Reed Sensors have been an excellent choice capable of accomplishing all three requirements in a reliable manner. Figure 1. MK17-X-3 Sensor physical layout Features • The reed switch used in the Reed Sensor is hermetically sealed and is therefore not sensitive rough wet environments • The reed sensors reliably operate between 50˚C to 150˚C Figure 2. Close-up of window motor with power off. • Magnet and Reed Sensor are isolated and have no physical contact by typically having the magnet mounted on the motor and the Reed Sensors mounted and positioned to accurately detect the motor rotation • The magnet is not affected by its environment • Tens of millions of reliable operations • Surface mount and through hole packages available • Cylindrical hole and screw fastening mounting • Contacts dynamically tested Applications • Ideal for sensing motor rotation associated with power windows • Ideal for applications sensing any kind of motor rotation in a host of different configurations Figure 3. Window motor is running and sensors sense rotation speed and direction. Power Windows End Points Are Reliably Controlled By Reed Sensors Power windows have undergone dramatic changes in the controls. Originally the end limits were controlled by mechanical limit switches that were subject to the environment, which would eventually effect their reliability over the useful life of the window. If one’s hand got caught between the window and the door, there was no way to sense this condition. Of course this resulted in some severely pinched and broken fingers. The designer developed away to sense when the motor slowed down which caused a surge in the current flow to the motor. This surge occurred when the window reached its end limits or when an object showed resistance to window movement. This approach improved the reliability and now detected the existence of a hand impeding the window from shutting. This approach had some flaws particularly when subjected to temperature extremes and used many costly electronic components. Designers finally discovered a clever way to solve all the problems associated with power windows in an economical way using MEDER’s reed sensors. MEDER electronic Application MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: [email protected] MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: [email protected] Page 1 of 3 www.meder.com Monitoring Vehicle Power Windows Using A Reed Sensor REED RELAYS REED SENSORS REED SWITCHES Specifications Operate specs Min Max Units Must close distance 5 25 mm Must open distance 5 25 mm Hysteresis Load Characteristics Switching voltage Switching current Carry current Contact rating Static Contact resistance Dynamic contact resistance Breakdown voltage Operate time Release time Operate Temp MK06 Storage Temp MK06 Operate Temp MK15 Storage Temp MK15 MK15 Typical 50% Min Max Units 200 0.5 1.5 10 150 200 V Amps Amps Watts mΩ mΩ MEDER’s reed sensors use hermetically sealed reed switches that are further packaged in strong high strength plastic, which virtually eliminates any environmental effects on their reliability particularly over the temperature extremes. The magnet is mounted on the motor and two reed sensors are mounted in a convenient manner detecting each rotation of the motor. Using two reed switches allows the designer to determine the direction of motor and therefore the direction of the window movement. The design of the motors used slow their rotation once they encounter any resistance. This is immediately sensed by the reed sensors showing the change in rotation speed, which in turn sends a signal to the electronics turning off the motor. In this way the end limits are reliably detected as well as the detection of any resistance to the window movement before it reaches its end limits. MEDER’s sensors are packaged for surface mounting as well as through hole mounting. Also, MEDER has cylinder packages and well as screw fastening packages having lead wires for remote attachment to the electronics. Surface Mount Series Series 320 -20 -35 -20 -35 0.5 0.1 85 85 130 130 V msec msec °C °C °C °C MK15 MK16 MK17 MK22 MK23MK23-35 MK23MK23-66 MK23MK23-87 MK23MK23-90 Dimensions mm W 2.5 H 2.5 L 19.50 W 2.3 H 2.3 L 15.60 W 2.1 H 2.1 L 9.61 W 2.7 H 2.3 L 15.60 W 2.2 H 1.95 L 15.75 W 2.2 H 2.7 L 19.60 W 2.0 H 2.1 L 15.60 W 2.54 H 3.05 L 24.9 Illustration inches 0.098 0.098 0.768 0.091 0.091 0.614 0.083 0.083 0.378 1.060 0.091 0.614 0.087 0.077 0.620 0.087 1.060 0.772 0.079 0.083 0.614 0.100 0.120 0.980 Figure 3. MK15 Tape & Reel MEDER electronic Application MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: [email protected] MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: [email protected] Page 2 of 3 www.meder.com Monitoring Vehicle Power Windows Using A Reed Sensor REED RELAYS REED SENSORS REED SWITCHES Through Hole Series Series MK06MK06-4 MK06MK06-5 MK06MK06-6 MK06MK06-7 Dimensions mm W 3.3 H 3.3 L 12.06 W 2.8 H 3.2 L 14.30 W 3.3 H 4.2 L 17.24 W 3.3 H 4.2 L 19.78 Illustration inches 0.130 0.130 0.475 0.110 0.126 0.563 0.130 0.165 0.679 0.130 0.165 0.779 Cylindrical Panel Mount Series Series MK03 MK03 Dimensions mm Dia 5.25 L 25.5 Illustration inches 0.207 1.004 MK14 MK14 Dia L 4 25.5 0.157 1.004 MK18 MK18 Dia L 5 17 0.197 0.669 MK20/1 MK20/1 Dia L 2.72 10 0.107 0.394 Rectangular Screw Flange Mount Series Series MK04 MK05 MK05 MK12 MK12 Dimensions mm W 13.9 H 5.9 L 23.0 W 19.6 H 6.1 L 23.2 W H L 14.9 6.9 32.0 Illustration inches 0.547 0.232 0.906 0.772 0.240 0.913 0.587 0.272 1.260 **Consult the factory for more options not listed above. ** MEDER electronic Application MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: [email protected] MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: [email protected] Page 3 of 3 www.meder.com