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Angle sensors + wireless

Discussion in 'Sensors and Actuators' started by GecinaWa, Sep 25, 2012.

  1. GecinaWa

    GecinaWa

    2
    0
    Sep 25, 2012
    Hey guys! I'm a mechanical engineer and I need to build a small circuit, hope you guys can help shedding some light onto it! :)

    All I need is to read the angle from several knobs and send these readings to a computer wirelessly. More than the precise angles, the important thing is detecting whether each knob is closer to a 0°, 90°, 180° or 270° position in real time.

    Specific requirements:

    - 5 to 12 knobs
    - The knobs must be able to turn indefinitely in any direction.
    - Any kind of information can be send to the computer, as long as it relates to the knobs' possitions.
    - The whole thing (sensors + circuits) has to be as small as possible (preferably fitting inside one's hand).

    My humble ideas so far:

    I thought of using potentiometers as the sensors, they're small and cheap, but I'm finding it difficult to get a precise reading from them, especially after a few turns.

    As for the wireless communication, I'm completely lost. Looked up RF transmitters and other more expensive alternatives and can't figure out what would be more suitable for my application. I need something small and simple.

    And finally, I have no idea ho to hook up the sensors to whatever wireless transmitter I'll be using...

    Thanks in advance for the help :D
     
  2. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    Use rotary encoders that is what they are for...

    Well 'simple' is arbitrary... You just need to pic a standard and run with it...

    A micro would read and measure the knobs and send serial data to the wireless module... And on the other end another micro would receive that information decode it and hand it off to the computer through whatever protocol...

    It's not a crazy hard task but it's involved, and if you don't have any micro programming experience or serial communication experience it might be over your head at this time...
     
  3. donkey

    donkey

    1,286
    56
    Feb 26, 2011
    coca is right as always, the only thing he hasn't touched on in a little more depth is transmission.
    you have so many different ways these days each has its own flaws and benefits.
    the first is infared like in your remote, then you move onto bluetooth, fm, uhf... the list is getting longer and longer.
    the big question is how far do you need to transmit?
    the 2nd big question is is there anything blocking the view from the knobs to the computer?if so what and how thick?
    if you are starting in under say 20metres range try the nRF24L01 which is 2.4ghz tranciever (both send and recieve) and they cost about $3 last I checked, great for experimenting. grab your microcontroller of choice and plug it up. PIC has it hobby side called PICduino which does not have the following of other but still has a pretty large community that will help.
    hope this helps you get started.
    the big thing is that the second you consider using a microcontroller you have to start looking at programming, most use C but there are others. hope you can figure it out
     
  4. GecinaWa

    GecinaWa

    2
    0
    Sep 25, 2012
    First of all, thanks for the answers, CocaCola and donkey!

    I forgot I had tried a bit of that already! I used this encoder: https://www.sparkfun.com/products/9117 . I hooked it up to an Arduino and wrote a simple code to make it give me the current closest position (0, 90, 180 or 270). It outputs integer values for the position (not sure now, but from 0 to about 200 I think) which grow/decrease with the direction I turn. But after a few moves, the error accumulated was so high that it was estimating the position wrongly. I should still have the code here somewhere, I'll look for it and see if you guys have an idea on how can I improve it :)

    I have some experience with Arduino and I've been experimenting with it, but it is too big for my task... By the pictures I saw, this PICduino looks as big... How would you suggest I get down to just the components I need?

    Do I absolutely need a microcontroller between the sensors and the transmissor? Or is there a way I can put together a few components to connect the encoders directly to the transmissor and do whatever processing I need only on the PC? I'm not as worried about programming as I am about space...

    Not too far, a few meters, maybe 5 at most. But there might be something between it and the PC, like people... no walls or anything like that.

    Cool, thanks for the suggestion! I'll get one of those to start experimenting with!



    Again, thanks for the help, I really appreciate it! :)
     
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