Help with directional lighting project, hall effect sensors etc

Discussion in 'The Projects Forum' started by Hoopdub, Feb 23, 2015.

  1. Hoopdub

    Thread Starter New Member

    Feb 23, 2015
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    Hi all, I’m hoping some of you may be able to help me with a project my employer has set me. It’s been many years since I have dabbled with electronics, and to be honest this is way beyond my capabilities.
    The brief, I have a railway trailer, now this trailer requires lights at each end, 2 white and 2 red. I have a 12v DC battery source. The lights need to display as follows,
    When stationary all 4 red lights on, 2 at one end 2 at the other. When trailer moves forward the lights switch to 2 white in the direction of travel and 2 red at the rear. If it changes direction on track then the lights must swap. So basically when it’s travelling it’s always displaying 2 white lights in the direction of travel and 2 reds at the rear, and when stationary switch to all 4 red lights.
    Currently it does this with a Hall Effect sensor and a magnet mounted on one of the rail wheels, the sensor is wired into a box. Here where I hit a problem. The box is resin filled so I can’t reverse engineer it. And having limited electronic knowledge I can’t work out how it works.
    The Hall Effect sensor is a Honeywell SR130 18-1.
    The company we buy these switching boxes from has gone bust and we have yet to find anyone who makes them elsewhere, hence me being the resident auto spark has been lumbered with the task of creating our own version.
    Any help greatly appreciated. Thanks in advance people.
     
  2. Hoopdub

    Thread Starter New Member

    Feb 23, 2015
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    Apologies the sensor is a 103SR18-1. but any variation to the system is acceptable as long as I can get it to do what its supposed to LOL
     
  3. #12

    Expert

    Nov 30, 2010
    16,261
    6,768
    First, there must be something about what is being sensed that changes according to direction. My first thought is 2 slots, one larger than the other. Then this information goes to a microprocessor to measure the time between the short and the long...or the long then the short, depending on which way the trailer is moving.

    Go examine the pick-up area and find out what makes the sensor know which way the trailer is moving.
    Watch for magnets.
     
  4. pwdixon

    Member

    Oct 11, 2012
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    I would get rid of the sensor and use a gyro and a micro to do the job with no external wiring or magnets on the wheels'.
     
  5. Hoopdub

    Thread Starter New Member

    Feb 23, 2015
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    we use magnets mounted on the wheel, and the sensor fixed to the axle as the wheel spins the magnet passes the sensor and changes the direction of the lights.

    here is the box, full of black goo, BOOO!
    [​IMG]

    and the sensor
    [​IMG]
     
  6. Hoopdub

    Thread Starter New Member

    Feb 23, 2015
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    oh also it switches the ground connection to the lights. the positive is permanent to the leds.
     
  7. Hoopdub

    Thread Starter New Member

    Feb 23, 2015
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    don't know if this will help with thte understanding of what I am trying to do. this is a drawing of a system I did on a different vehicle that was hydraulically driven, where the forward and reverse signals came from pressure switches fitted in the hydraulic lines.

    [​IMG]

    with the trailers as they are not self propelling I cant use pressure switches, that's where the hall sensor and magnet come in.

    sorry if this confuses things, im not very good at explaining myself
     
  8. pwdixon

    Member

    Oct 11, 2012
    488
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    Wow and I thought you were talking about model railways, this is a real application! Even better reason to solid state.
     
  9. Hoopdub

    Thread Starter New Member

    Feb 23, 2015
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    Haha yes this is the big stuff lol. mainly rail going excavators and plant, along with big trailers.
     
  10. Reloadron

    Active Member

    Jan 15, 2015
    963
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    Looking at the sensor used it seems to be a latching type Honeywell Hall Effect Sensor. Detecting rotation or speed isn't an issue, what I am not sure about is how using this particular sensor they manage to get direction like a quadrature sensor would be used for. Monitoring pulses would seem easy enough as in Yes, it's moving or No it is stationary but the direction has me stumped using the sensor that is in use?

    Ron
     
  11. pwdixon

    Member

    Oct 11, 2012
    488
    56
    So are there two magnets on the wheel?
    If there are two are they spaced equally around the wheel?
     
  12. pwdixon

    Member

    Oct 11, 2012
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    It's not relevant to the problem but what country are you in?
     
  13. Hoopdub

    Thread Starter New Member

    Feb 23, 2015
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    sorry this may be down to the way im explaining. we fit 2 magnets to the wheels for the sensor to pick up. im uploading more pics now. they magnets are very strong one has a south pull the other a north pull.
     
  14. Hoopdub

    Thread Starter New Member

    Feb 23, 2015
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    the magnets are places right next to each other in one place on the wheel, so it has to do a full revolution for the sensor to pass them again. im in the UK btw. I assume the latching side of it must be linked to a timer in the box because if the trailer becomes stationary for roughly 5 seconds then the lights switch to red all round. as they should do.
     
  15. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
    2,369
    Can you give a little more detail as to how the magnets and sensor are mounted in relation to each other, you mention the sensor is on the axle? if the axle and wheel turn together how does it change relationship?
    Max.
     
  16. Hoopdub

    Thread Starter New Member

    Feb 23, 2015
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    heres how we mount the sensor
    [​IMG]

    and both magnets are placed here side by side
    [​IMG]

    and heres the magnet, south pull type, north looks the same
    [​IMG]
    [​IMG]
     
  17. MaxHeadRoom

    Expert

    Jul 18, 2013
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    It would seem to me the the sensor being a magnetic latch type, sees the last one so the latch is set to this pole, if it does not see any change for a prescribed time, it considers the car stationary.
    A circuit should be fairly simple.
    Is there any external relays for actually switching the lights?
    Max.
     
  18. Hoopdub

    Thread Starter New Member

    Feb 23, 2015
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    Sounds about right there Max :)
     
  19. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Thinking a little more on the logic, It could be that if one pole is sensed then what happens if the car is moving extremely slow, it will take some time to appear at the next pole, in the meantime the circuit may think it is actually moving in the opposite direction, also at some point in time it has to decide it is actually stationary, whether on a pole or not.
    It may involve a small micro?
    Max.
     
  20. Hoopdub

    Thread Starter New Member

    Feb 23, 2015
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    hmmm, had not considered that. but yes you are correct, if its going slow enough it will think its stationary. I don't think this is a big problem with our application. as good as it would be to have it work at all speeds, I don't know how easy or difficult it would be to do this. or cost effective.
     
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