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Monitoring a swimmer's arm movement

Discussion in 'General Electronics Discussion' started by Andrea Bogazzi, Oct 6, 2014.

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  1. Andrea Bogazzi

    Andrea Bogazzi

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    Oct 6, 2014
    Hi everyone,
    I need to start a project to monitor some simple event and i need some advice.
    What i have to monitor is the arm of a swimmer completing the around body movement.

    What i need to build is a sensor that with bluetoot speak with a device ( tablet or phone ).
    i was looking around for sensors ( hall effect, or some magnetic compass ) and the bluetooth.

    I don't need an analog value , i just need to get the on/off event.
    So i was searching some sensor and some bluetooth module to connect toghter with a battery ( and then writing the software ).

    I got lost searching for hardware, i hoped to find a module that had integrated bluetooth pairing and an input to work like a "serial port". So i think that i'm talking about "bluetooth + some simple cpu". ( correct me if i'm wrong)

    For the sensor itself i was thinking of something that can be activated by a magnet passing nearby.

    I'm searching suggestion for both of the parts.
    Anyone willing to help?

    Some link to some model.
    As you can understand i'm not electronic expert, but i think i can manage it with some learning failures.

    Regards, Andrea
     
  2. Andrea Bogazzi

    Andrea Bogazzi

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    Oct 6, 2014
  3. Gryd3

    Gryd3

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    Adafruit and sparkfun have plenty of bluetooth modules. All I've seen so far require an additional microcontroller to feed serial data to the bluetooth module though.
    Expanding on your idea may help as well
     
  4. Andrea Bogazzi

    Andrea Bogazzi

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    Oct 6, 2014
    Thank you for reply.
    What i need to do is cath a hand passing near a sensor, and transmit this information to a tablet with bluetooth.

    So you suggest me to start with arduino + bluetooth + sensor?

    For the sensor i was thinking about hall effect or a digital compass + magnet. If there are bettere ideas... i will be happy to get them.
     
  5. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Unless you can get the swimmer to move a magnet on his/her arm within a few inches of the sensor every time, I don't think magnetic detection would be the answer. Perhaps a digital compass attached to the swimmer's arm, or a G sensor.

    Are you able to attach anything to the swimmer's arm? If not, you might need to use a broken beam to detect the movement. Is the swimmer going to be moving or stationary? Could you detect the arm movement by detecting movement in the air as it goes past? Or detecting movement in the water?
     
    Last edited: Oct 17, 2014
  6. Andrea Bogazzi

    Andrea Bogazzi

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    Oct 6, 2014
    is the same, i can gather the data that is most suitable and by software detect round trip. I don't have to detect the exact movement, but just the around trip.

    few inches, so 2 - 3 inches is 7cm would be already enough between arm and leg for example. Is just a start, i know that 3 axis g sensor + 3 axis gyro would give me more chances, but i'm scared of 1) connecting to the micro controller, 2) analyze all this data as a first project.
    So for getting started a single current drop from hall sensor OR a digital compass going crazy for the magnet would be something to start with, maybe simpler.

    Anyway the idea was something on the arm ( a bracelet ) and something small on the swimsuit .

    I'm still at the stage "how do i connect all those piece togheter?"
    so i want to start slow.

    thanks again.
     
  7. shrtrnd

    shrtrnd

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    I don't have much to add, but I'm curious about the project. Are you trying to determine how many strokes are used per lap? Or what is the purpose of the monitor?
    This doesn't sound like it helps improve the swimmer's performance, so I was just wondering what the purpose of the test is for.
    I used to swim competitively, and I'm wondering about exactly why you're trying to do this.
    For example: Some swimmers breathe every second stroke, and some take several strokes before breathing. If you had a tilt switch on the swimmer's google, you could simply count the number of times
    the swimmer turned his head to breathe.
    The magnets/hall effect switch was interesting (wrist band and switch on trunks), but the width of the swimmers stroke away from the body would vary with the stroke style.
    Are you dealing with freestyle, butterfly, breast, backstroke in particular, or are you trying to come up with something that will work for all?
    For freestyle or butterfly as an example, some type of tilt switch on a wrist or armband alone (with micro-tranmitter) might work. If the swimmer tripped the switch on the forward stroke and again on recovery, you'd just
    divide the number by two, to tally one complete stroke.
    Anyhow, it might help with ideas, if we know the PURPOSE of the count.
     
  8. Andrea Bogazzi

    Andrea Bogazzi

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    Oct 6, 2014
    The purpose is to get how many stroke does the swimmer every minute. Main purpose is freestyle, this is for monitoring own training.
     
  9. shrtrnd

    shrtrnd

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    Jan 15, 2010
    Alright. As you are probably aware, no swimmer is going to WANT to wear anything that produces drag.
    I know from my own experience that swimmers are very predictable in their personal swimming style. I only knew one guy who varied in this, but you may be seeing something different in the swimmers you're
    monitoring. We breathe the same way almost all of the time. Either every stroke, or every other one. I may be wrong concerning your people, they may not be predictable.
    What about the idea of a tilt switch on the google. Counting the number of times the swimmer breathes, and matching that number with the number of strokes the swimmer makes between breaths?
    Because of the differences in swimming style, I'm hard pressed to think of an unencumbering way to attach something to a swimmer which will accurately tally arm rotations.
    Maybe somebody else here will have a better idea. Good luck with the project.
     
  10. Andrea Bogazzi

    Andrea Bogazzi

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    Oct 6, 2014
    mmm tilt switch is a good idea.
    easyer.
    Anyway i still need help to connect a switch to bluetooth adpater and send it as a serial event.
    Tilt.... tilt... tilt....
    Still micro controller needed?
     
  11. shrtrnd

    shrtrnd

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    Jan 15, 2010
    I'm not familiar with the new tech stuff. You'd need a micro transmitter to count each switch closure, and a receiver to register the closures.
    Somebody else here is probably fluent in what you could do with the tally.
    Number of switch closures per lap, your one-minute count goal, probably other capabilities.
    Just wanted to give you another option to consider as the magnets/hall effect idea seemed iffy to me because of physical variances in stroke.
    The common denomiator to me, is that they all have to breathe sometime, and if you can match that with the number of arm rotations, you'd have your count.
     
  12. Gryd3

    Gryd3

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    Jun 25, 2014
    If you manage to build it small enough, you could use a gryo, accelerometer or both.
    Tilt switch is another option, but the above would allow you to track motion of the arm. If you can manage, I'm sure you could make it about the size of a watch.
    You can analyze the data on a computer to view length (time) of stroke, angle of the arm during stroke, etc.
     
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