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Discussion in 'General Electronics Discussion' started by jim bcp, Aug 28, 2018.

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  1. jim bcp

    jim bcp

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    Apr 2, 2014
    Am trying to find someone to do a small electronic development project
     
  2. Minder

    Minder

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    Apr 24, 2015
    "to do" is that design from the ground up or put a board together and build or all three?
    M.
     
  3. jim bcp

    jim bcp

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    Apr 2, 2014
    I'm an inventor, not an electronic engineer so some of my terminology may not be right or professional. We are using a rotary encoder with a slotted disc and an optical coupler to measure the movement of a lever. We want to change the encoder to an accelerometer sensor, using the change in levels of the lever, to replace our present encoder. The signal from the accelerometer has to be processed to supply the same type of signal that the old encoder produced.
     
    Last edited: Aug 29, 2018
  4. Minder

    Minder

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    Apr 24, 2015
    What is the present output or device controlled by the accelerometer?
    What is the reason for changing the encoder and why is it not working for you?
    How is the process managed at present? Microprocessor? Logic etc?
    M.
     
  5. kellys_eye

    kellys_eye

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    Jun 25, 2010
    An accelerometer will only measure the RATE of change, not the absolute position.
     
  6. jim bcp

    jim bcp

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    Apr 2, 2014
    Like I said I am not an electronic engineer.
    The output is from a Honeywell Optical Coupler # HOA0901-011. The signal from this goes to a microprocessor.
    The encoder we are using now, works fine, but we want to eliminate all mechanical parts.
     
  7. BobK

    BobK

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    Jan 5, 2010
    As will most rotary encoders. Yes, there are some that give absolute position, but that is not the norm.

    You can get change in position from an accelerometer by integrating it twice.

    Bob
     
  8. Minder

    Minder

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    Apr 24, 2015
    You can get small totally enclosed quadrature encoders in place of the slot opto, which I would not expect to be any higher resolution than 100 p/rev.
    It would also give you an absolute reference point if needed via the Marker.
    IOW it might pay to just improve on the existing if it is working for you?
    M.
     
  9. kellys_eye

    kellys_eye

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    Jun 25, 2010
    ....so you want to eliminate physical movement too? If something 'moves' you have 'mechanical parts'.
     
  10. AnalogKid

    AnalogKid

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    Jun 10, 2015
    What I hear:

    Rather than couple the moving lever to a disc that rotates near an optical switch, you want to mount an accelerometer directly on the lever and run the flexible signal wires to the processing circuit, eliminating the mechanical alignment needed for the slotted disc / optical switch. Yes?

    ak
     
  11. Minder

    Minder

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    Apr 24, 2015
    Was this developed by you?, or for you?, or was it some off the shelf equipment?
    If the former, what processor was used?
    What is the reason for a desire to change the present set up?
    M.
     
  12. jim bcp

    jim bcp

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    Apr 2, 2014
    ak
    That is right. I want to eliminate the mechanical parts of the rotating disc.
     
  13. Alec_t

    Alec_t

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    Most 3-axis accelerometer modules (MEMs) can sense Earth's gravity resolved along the axes, hence can sense tilt.
     
  14. jim bcp

    jim bcp

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    Apr 2, 2014
    M.
    It was developed for me using the #87C751 Microcontroller.
    The reason to change the present set up is to eliminate the mechanical parts, such as the slotted disc.

    jim bcp
     
  15. AnalogKid

    AnalogKid

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    Jun 10, 2015
    What are the signals going to the uC: 1 sine/square wave, 2 sine/square waves (quadrature), something else?

    ak
     
  16. kellys_eye

    kellys_eye

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    Jun 25, 2010
    What level of accuracy do you require?
     
  17. Minder

    Minder

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    Apr 24, 2015
    Typically the slot opto quoted and a slotted disc would be quadrature signals.
    M.
     
  18. AnalogKid

    AnalogKid

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    Jun 10, 2015
    I had not pulled up the datasheet yet; I see that now. Turning the outputs of one or more accelerometers into the equivalent quadrature squarewaves is going to take some number crunching. I get the desire for something that is reverse compatible at the interface connector so it can just be plugged into the existing controller, but that makes for a lot of extra work.

    ak
     
  19. jim bcp

    jim bcp

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    Apr 2, 2014
    The level of the lever changes by approximately four tenths of a degree for each slot of our slotted disc in our present encoder.
    The accuracy in not tremendously critical.

    jim bcp
     
  20. Minder

    Minder

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    Apr 24, 2015
    If the change is due to the exposed/fragility of the slotted disc, are you sure it would not benefit simply by replacing it with a enclosed/sealed rotary encoder? The only thing exposed is the rotor shaft.
    M.
     
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