How can i know the angle of the vertical window blind by placing a small sensor on one of the blind slat

i am trying to make a arduino/esp8266 controlled window blinds, the controlling can be easily achieved in horizontal blinds, but my apartment has a vertical blind which are not interconnected at the bottom

Tried so far:

  1. open and close based on time which it takes to open and close, but it keeps drifting over time

  2. Cannot use light sensor to sense the ambient light, does not give correct information (day and night)

  3. Tried to put a potentiometer on top of one of the blind slat ( no enough room to place things there, potentiometers have more friction)

any suggestions for angle sensor ?

  • Is this the sort of bind where you open / close or by turning a stick, or by pulling a string? Could you just start it in a known position, and let it keep track of where it is by how far it has turned - use a stepper motor so that you have predictable control of the movement. – Mark Smith Aug 19 '17 at 14:41

A hall-effect sensor, plus a small magnet attached (glue?) to the outside edge of one slat ought to be able to tell you the strength of the magnetic field, and thus the distance of the magnet from the sensor. From that, given that the rotation is with a fixed radius, you can deduce the angle while introducing zero additional friction.

Edit: I had imagined something like:

Hall Effect Sensor placement on blind slat

However, looking again, this introduces difficulty in detecting the 90deg position, where the magnetic flux lines are exactly parallel to the hall-effect sensor plane.

If you experiment with this enough, you may be able to get repeatable values from the sensor to know the angle of the blind slats.

Edit 2:

The timing measure you noted in your question could also be a possibility. If you could use a microswitch or photo-interrupt sensor on the extreme ends of travel (0deg and 180deg), so that any time those extreme ends are detected, you can eliminate drift.

  • Ya this sounds to be a good idea, Actually I can have a small magnet fixed to the bottom end of one of the slat, and place the hall effect sensor below it fixed to the base( i have some room below the slats for my window) , do you have good suggestions for cheap hall effect sensors with rotating magnetic field .. Thanks @ Jose – user2345 Aug 18 '17 at 18:28
  • just to know, does the hall effect sensor give you absolute value even when it loses power – user2345 Aug 18 '17 at 18:33
  • If the sensor loses power, it doesn't work. If you mean, does it have to start from a "known value" after the power returns, then the answer is yes, it gives an absolute value. It measures magnetic flux through the plane of the sensor, which is not dependent on any initial position when power is first applied. – jose can u c Aug 18 '17 at 18:53
  • A hall-effect sensor isn't going to work that way. It detects/senses magnetic flux "through" it, so simply rotating the magnet without moving it in the X or Y position relative to the sensor will not be detectable. – jose can u c Aug 18 '17 at 19:40

How to get the angle from vertical window blinds

vertical blinds have by definition a 90degree angle.

unless "angle" means something else to you.

  • I believe each strip can rotate around the vertical axis, though... – jose can u c Aug 18 '17 at 17:42
  • each strip has ~180 degrees rotation angle along its own vertical axis – user2345 Aug 18 '17 at 17:45
  • In that case, tie a weighty item at end of a rope and wind it over the shaft of a potentiameter. you can measure that potentiamiter's resistance by charging up a capacitor with it, or via an adc. – dannyf Aug 18 '17 at 20:49

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