Electric Electric Toothbrushes Toothbrushes Achieve Much Greater Reliability Using Reed Sensors REED RELAYS REED SENSORS REED SWITCHES Introduction For years manufactures of electric toothbrushes have used mechanical slide switches to turn on and off the power to the toothbrush. The mechanical slide switches are subject to very harsh environments having to deal with chemically active toothpastes, acidic saliva, and running water at various temperatures and acidity/alkalinity levels. This environment attacks the electrical contacts in the slide switch and in many cases, after a short time the slide switch fails to turn the toothbrush on and off. Going to a Reed Sensor has eliminated this problem. Figure 1. MK17-X-3 Sensor physical layout Features • Reed contact is seal in the casing of the toothbrush • Reed contact never comes in contact with the outside environment Figure 2. Magnet slide in ON position activates Reed Switch • Reed switch is hermetically sealed • Magnet and switch are isolated by the toothbrush casing • The magnet is not affected by the environment • Millions of operations reliably • Surface mount or thru hole mounting • Contacts dynamically tested Applications • Electric toothbrush • Activation approach may be used anywhere when concerned about switching in a dirty environment (dust, dirt, moisture, acidic environment, alkaline environment) Figure 3. Magnet slide in OFF position deactivates Reed Switch Harsh Switching Environments call for fully sealed Reed Sensors Electric toothbrushes have had reliability issues for years because of the faulty operation of the use of on/off mechanical slide switches that are not fully sealed from the environment. To prevent this designers have had to go to fully sealed slide switches which are much more expensive are still subject to some reliability issues dealing with the sealing of the slide switches. The mechanical slide switches are still subject to very harsh environments having to deal with chemically active toothpastes, acidic saliva, and running water at various temperatures and acidity/alkalinity levels. This environment, if it leaks into the seal will attack the electrical contacts in the slide switch and in many cases, after a short time the slide switch fails to turn the toothbrush on and off. 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 Electric Electric Toothbrushes Toothbrushes Achieve Much Greater Reliability Using Reed Sensors REED RELAYS REED SENSORS REED SWITCHES Specifications Defining the MK06 MK06 & MK15 Series Operate specs Min Max Units Must close distance 5 15 mm Must open distance 5 15 mm Hysteresis Load Characteristics Switching voltage Switching current Carry current Contact rating Static Static Contact resistance Dynamic contact resistance Breakdown voltage Operate time Release time Operate Temp MK06 Storage Temp MK06 Operate Temp MK15 Storage Temp Temp MK15 Typical 50% Min Max Units 200 0.5 1.5 10 150 200 320 -20 -20 -20 -20 0.5 0.1 85 85 130 130 V Amps Amps Watts mΩ mΩ V msec msec °C °C °C °C The Reed Sensor is the best approach to solving this problem. It solves the reliability problem and represents a low cost solution. The on/off switch must be able to handle the following: 1. survive a bathroom atmosphere; 2. be able to survive being dropped three or more feet; 3. survive repeated contact with saliva (acidic); 4. survive contact hot and cold water baths; 5. and continue to work for several years. The electronics are not affected by the above environment because they are safely packed away internally in the casing of the toothbrush. So the most vulnerable component is the on/off switch. The key feature of the reed sensor is its main component, the hermetically sealed reed switch, is also locked away in the sealed casing of the toothbrush where the other electronic components reside. A magnet is molded into the plastic form replacing the slide switch. When the molded magnet slide is moved, its magnetic field influences the strategically placed reed switch internal to the casing closing the contacts; thereby turning on the toothbrush operation. In a like manner when the magnet slide is slid back the magnetic influence is lost to the reed switch, opening the contacts and turning off the toothbrush. In this case, the magnet and its molded slide mechanism never comes in physical contact with the reed switch. This sets up the biggest single reason why this approach represents the best technology for the design. Consider some of the below options in surface mount and through hole versions for an electric toothbrush or other similar application using a sliding switch to power a handheld device. Surface Mount Series Series MK15 MK16 MK17 MK22 MK23MK23-35 MK23MK23-66 Figure 4. MK15 Tape & Reel MK23MK23-87 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 12.15 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 Illustration inches 0.098 0.098 0.768 0.091 0.091 0.614 0.083 0.083 0.478 1.060 0.091 0.614 0.087 0.077 0.620 0.087 1.060 0.772 0.079 0.083 0.614 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 Electric Electric Toothbrushes Toothbrushes Achieve Much Greater Reliability Using Reed Sensors 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 **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