Brake Pedal Position Sensor REED RELAYS REED SENSORS REED SWITCHES Introduction When depressing the brake pedal, the auto's hydraulics engage and slow or stop the vehicle. In addition, two other functions can also occur, one of which is critical to the operation of the vehicle- disengaging of the cruise control. The other function is to switch on the brake lights to alert other vehicles that the car is slowing down and/or is going to stop. In the past, these latter two items typically used electromechanical sensors to sense the brake pedal motion but failed to disengage the cruise control, allowing the engine to continue its race forward increasing the possibility of a potentially dangerous collision. MEDER's automotive sensor designers have successfully solved the reliability problem by using reed sensor technology. Figure 1. KSS Sensor physical layout Features • Ability to withstand harsh temperature swings • Available in a Form A (normally open) and a Form B (normally closed) • Designed to handle high shock environments • Designed to operate in dirty environments • Dynamically tested contacts • Hermetically sealed • Millions of reliable switching operations Figure 2. Brake Pedal is up and both Reed Switches are closed, Rear brake lights off and cruise control indicator is lit. • Not sensitive to ESD and EMI Applications • In a moving vehicle, monitor the movement or position of the brake pedal to directly activate brake lights and reliable turn off cruise control Figure 3. Brake Pedal is depressed, Reed Switches open activating rear brake lights and disengaging the cruise control. 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 4 www.meder.com Brake Pedal Position Sensor REED RELAYS REED SENSORS REED SWITCHES Specifications (@ 20° 20°C) KSS Series Brake Pedal Operation Practically all motor vehicles have a brake pedal that is used to slow down or stop a vehicle. When the operator applies their foot to the brake pedal three events must happen: Operate specs Min Max Units Must close distance ref ref mm Must open distance ref ref mm 1. 2. 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 Storage Temp Min Max Units 200 0.5 1.25 10 250 V Amps Amps Watts mΩ 250 mΩ 225 0.5 0.1 -20 80 -50 125 V msec msec °C °C 3. The brake shoes need to immediately apply pressure to the brake pads lining the inner diameter of the wheel. This happens directly using hydraulics which activates the braking action slowing down or stopping the vehicle. A sensor is activated turning on the brake lights. These lights alert other vehicles in the rear that this vehicle is either slowing down or stopping, reducing the possibility of a rear end collision. Most vehicles today have cruise control as a standard option. When the brakes are applied a sensor must be activated that in turn, disengages the cruise control, automatically reducing gasoline flow to the engine, allowing the vehicle to slow or stop. The brake pedal is generally located near the floor of the vehicle in one of the dirtiest environments in the cab of the vehicle. Also, a person’s shoes pressing against the brake pedal may have water, dirt, grease, oil or grime being constantly applied to the pedal over long periods of time. Electromechanical sensors, being exposed to this environment will experience contamination adversely affecting their switching contacts producing unreliable brake switch operation. Electromechanical sensors can be the least costly approach. When only the brake lights were being sensed and the electromechanical sensor failed, although considered dangerous, was not necessarily an accident waiting to happen. However, with the advent of cruise control, if the sensor fails to sense the brakes being applied, and therefore does not disengage the cruise control, a very dangerous situation will develop. The engine will want to race forward while the operator is trying to brake the vehicle. Reed Switches are therefore reed sensors are hermetically sealed and are the perfect solution for dirty environments. Reed sensors are rated to successfully switch hundreds of millions of operations, and are now the competitive choice for automobile engineers where they are now the preferred technology. The engineers are now finding reliable braking operation when the braking sequence occurs using reed sensors. Depending upon space availability, the sensor presented above will work very well. However, if space is limited our smaller MK15, MK16, or the MK17 series with their added over-molded protection are ideal. Other series may also be advisable depending upon the exact physical layout. The sensors can also be supplied as a single pole normally open and a single pole normally closed. In the second case, when the brake pedal is depressed, the normally closed contact will open automatically disengaging the cruise control. Consult with our engineers for specific details for your exact application. 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 4 www.meder.com Brake Pedal Position Sensor REED RELAYS REED SENSORS REED SWITCHES Consider some of the below options in surface mount and through hole versions for the brake pedal sensor or other similar applications. Surface Mount Series Series 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 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 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 0.478 1.060 0.091 0.614 0.087 0.077 0.620 0.087 1.060 0.772 0.079 0.083 0.614 0.100 0.120 0.980 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 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 4 www.meder.com Brake Pedal Position Sensor REED RELAYS REED SENSORS REED SWITCHES 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 inches 0.547 0.232 0.906 0.772 0.240 0.913 0.587 0.272 1.260 Threaded Panel Mount Series Series MK11 Stainless steel Dimensions mm inches Thread / M5 x 0.5 L MK11/M8 MK11/M8 Plastic L MK11/B MK11/B Brass Illustration 25.0 0.984 Thread / M8 x 1.25 38.0 1.496 Thread / M6 x 1.00 Thread / M8 x 1.25 Thread / M10 x 1.00 Thread / M10 x 1.00 L 38.0 1.496 **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 4 of 4 www.meder.com