Reed switches and Reed sensors in Sewing machine pedals

Sewing machines help stitch fabric, leather or other synthetic materials by using a needle and two thread feeders. In the modern electric machines, the pedal use a Potentiometeric controller similar to a ceiling fan. This consists of  wound coil with a moving carbon brush to control speed of the stitching motor. As the pedal is pressed, variable current is fed to the motor.

The disadvantage of such a system is that the carbon brush wears out and the stitching speed varies over time. A reed sensor array inside the pedal housing with a magnet mounted under the pedal, actuates each of the the reed sensors one by one as the pedal is depressed. The circuit that uses these multiple reed sensors is based on the same principles as level sensors.

The output from the reed sensors is suitably decoded and is used to control the motor speed. This way, the stitching speed remains constant with respect to the depressed position of the foot pedal and there is no chance of dirt or oil affecting the system. In more advanced sewing machine models, the number of mechanical parts have been reduced and reed sensors are even used to change state of the bottom bobbin thread feeders, whenever the shaft comes down and again when the shaft starts moving up.

Application Classification

Applications are classified as Position Sensing, Pulse Counting, Electromagnetic or Relay, Temperature Sensing or Magnet Biasing types. This application is classified as follows and the link gives more information on best practices to help select the most suitable AT band and matching magnet.

Position sensing Type

When an application requires the end position of a movement sensed, or the sensing of a part when it comes into a zone, or when the Continue reading -> Sep 29, 2024

Recommended Products

The Reed Switches and Sensors used in such applications need to be robust, durable and efficient in meeting a high life expectancy. Our engineers work hard in life testing our products under various conditions, and our intention is to ensure end product durability and life. Although we wouldn’t want to restrict any of our products for use in only certain applications, the recommended products for use in this application are listed below.

Micro Miniature PCB Mountable Reed Sensor, MS-105

Drawing of MS-105 Reed SensorDrawing of MS-105 PCB Pad Layout starFeatures10W Contact Rating. 12.7 mm PCB Pitch. Normally Open Continue reading -> Sep 29, 2024

Reduced Miniature PCB Mountable Reed Sensor, MS-106

Drawing of MS-106 Reed SensorDrawing of MS-106 Reed Sensor Pad Layout starFeatures10W Contact Rating. 15.2 mm PCB Pitch. Normally Continue reading -> Sep 28, 2024

M5 Threaded Sensor Cylindrical Sensor, MS-225

MS-225 Threaded Magnet Sensor drawing starFeatures10W Contact Rating. Normally Open contact. Three sensitivity bands. Sputtered Continue reading -> Sep 28, 2024