Automatic Convertible Roofs Use Reed Sensors To Control The End Points REED RELAYS REED SENSORS REED SWITCHES Introduction Particularly in warm weather areas convertible automobiles are very popular; however, surprisingly, even in cold weather areas, convertible autos are also very popular in the summer, warm weather months. In these areas, as the evenings cool or sudden weather conditions develop, the convertible roofs may need to be closed in a hurry. Most of the convertibles have gone over to automatic opening and closing. Reed sensors play a key role in accomplishing this. Figure 1. MK14 Sensor physical layout Features • The Reed Sensor never comes in contact with the actual movement of the convertible roof • The reed switch used in the Reed Sensor is hermetically sealed and is therefore not sensitive to dirty, oily, extreme temperature environments Figure 2. Showing convertible top in open position. Motor turned off and reed switch is activated. • Magnet and Reed Sensor are isolated and have no physical contact by typically having the magnet mounted to the convertible roof and the Reed Sensors are mounted and positioned to detect the end limit positions • The magnet is not affected by its environment • Capable of operating between -50˚C to 150˚C • Millions of reliable operations • Cylindrical hole and screw fastening mounting • Contacts dynamically tested • Large sensing distances possible Applications Figure 3. Showing convertible top in closed position. Motor turned off and reed switch is activated. • Reed Sensors are ideal for use in convertible cars for detecting roof end positions Convertible Roofs And Their End Positions Are Controlled By Reed Sensors • Anywhere for applications sensing any kind of end position movement even in dirty, extreme temperature environments Many of the older convertible cars used mechanical hand operation to collapse convertible roofs and to re-close the roof. This was a difficult task and many times the folds would not sit correctly making it difficult to seal off in the collapsed condition. Then motors were added to collapse (open) and close the roof, but if the motor was not stopped at the exact closed position and driven into its seating position or enclosure, damage could occur. This damage can occur whether the roof is traveling to the open position or traveling to the closed position. Designers finally selected MEDER’s reed sensors to solve the problem at the end positions. A magnet is mounted to the convertible roof and the reed sensors are mounted at the end positions. When the vehicle operator throws the switch to open the roof, a motor is engaged and the roof begins to open. 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 2 www.meder.com Automatic Convertible Roofs Use Reed Sensors To Control The End Points 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 Hysteresis Load Characteristics Switching voltage Switching current Carry current Contact rating Static Contact Contact resistance Dynamic contact resistance Breakdown voltage Operate time Release time Operate Temp Storage Temp Typical 50% Min Max Units 200 0.5 1.5 10 150 200 320 0.5 0.1 -40 150 -50 150 V Amps Amps Watts mΩ mΩ V msec msec °C °C This operation will continue until the end position is about to be reached. This is when reed sensor engages, sending a signal to the on-board computer, which sends a command to turn off the motor. The roof comes to rest in its fully open, nested position. When the switch is thrown to close the roof, the reverse happens. The motor is engaged and as the roof approaches the end position, the reed sensor closes, sending its signal to the computer, and it executes the turn off control of the motor. The roof now sits in its final closed position. These actions will happen reliably over the life of the vehicle. The reed sensor is a excellent choice because it can operate reliably from -50˚C to 150˚C and represents an economical way to carry out the sensing function. Because MEDER’s sensors use hermetically sealed reed switches that are further packaged in strong high strength plastic, they can be subject to rough treatment and environmental concerns such as dirt, grease, and moisture without any loss of reliability. MEDER has cylinder packages as well as screw fastening packages having lead wires for remote attachment to the electronics. Also, because of the multitude of design requirements, MEDER, in a matter of fact manner, has the capability of developing specialized packaging for both the reed sensor and the magnet to meet the user’s specific needs. Consider some of the below options in cylindrical and rectangular versions for end position/limit sensors or other similar applications. 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 Dimensions Dimensions mm W 13.9 H 5.9 L 23.0 W 19.6 H 6.1 L 23.2 Illustration inches 0.547 0.232 0.906 0.772 0.240 0.913 W 14.9 0.587 H 6.9 0.272 L 32.0 1.260 **Consult the factory for more options not listed above. ** MK12 MK12 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 2 www.meder.com