J-Tech Engineering - Product Subpage - micromods

By: J-tech Engineering  09-12-2011
Keywords: magnet, microcontroller, Position Sensor

 Digital Trimming Potentiometer

The digital trim-pot (digpot) is a response to a need by joystick manufacturers to have a lit display on the face of their equipment. Buttons on the face plate can be used to increase or decrease output voltage, while providing operator feedback in the form of a LED bar showing the output at any given moment. The output follows an acceleration curve when one of the momentary switches is initially actuated. Initial response will be slow permitting fine-control of output devices, however after aproximately 500mS, the output will change much more rapidly.

The module has the following feature set:

  • Microcontroller based input device
  • 5V supply voltage
  • Eight (8) LEDs, staged in colour: four green; three yellow; one red.
  • Switch inputs for up/down controls, any normally-open momentary switch can be used.
  • 0.5-4.5V linear output
  • Non-volatile option available (default switches to minimum voltage on reset).
  • Resettable fuse protection on power and return signal lines. Voltages to 24V tolerable.

The below diagrams are sampled data of a production unit showing the transition from minimum output voltage to maximum and back to minimum.


 Hall-Effect Linear Position Sensor

The linear position sensor works in conjunction with a magnet to sense position of a plunger type switch. The monitor is self-calibrating to the magnet, and will automatically set itself up each time the unit is powered up.

The module has the following feature set:

  • Microcontroller based input device
  • 5V supply voltage
  • ø0.125"x0.100" magnet required (supplied with monitor)
  • 0.150" travel of magnet is linearised to output (0.5-4.5V).
  • Overvoltage protection (up to 24V) with resettable fuses.

These sensors are ideal for foot-pedal, joystick or any equipment where a potentiometer might be used to sense position.

A hall-effect sensor is a linear device by nature, giving a linear deflection of voltage based on the intensity of the magnetic field present. Unfortunately, the variation in magnetic field intensity with proximity to a permanent magnet is far from linear.

The curve shown at left illustrates the uncorrected output voltage seen by a Hall effect sensor as a permanent magnet moves through its range of motion. The X axis shows the proximity of the magnet to the sensor, and the Y axis shows the uncorrected output voltage.

The effect on switch position is as follows: When the magnet is farthest from the sensor, a large amount of motion is required to influence the output, whereas when the magnet is close to the sensor, a minute change in position results in a large change in output voltage. It is this effect which the on-board microcontroller corrects.

Keywords: Hall-effect Sensor, magnet, microcontroller, Position Sensor

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