Looking for ideas

Discussion in 'The Projects Forum' started by higgy, Mar 30, 2010.

  1. higgy

    Thread Starter New Member

    Sep 5, 2009
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    I need to take a Hall Effect sensor and use it to control a relay in a 12 volt circuit. Needs to be weather resistant and tamper proof. Looking for ideas on the best way to go about it.
    Thanks for any and all suggestions.
    higgy
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    You state some conditions that suggest some intended placement -
    Why is that? Where is that? What is the 12 volt circuit, and the load in amps?
     
  3. retched

    AAC Fanatic!

    Dec 5, 2009
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    You could put it in an outdoor safe. :)

    Are you using this for a door sensor or security system?
     
  4. loosewire

    AAC Fanatic!

    Apr 25, 2008
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    I used to hid a 12 volt car battery In the woods to power experiments,or
    just leave the battery so I would not have to handle It.You think you are
    In the woods alone.The batteries always came up missing,If you leave
    any thing of value It will be gone. Who take these things.
     
  5. higgy

    Thread Starter New Member

    Sep 5, 2009
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    The idea is to use the signal generated by a vehicle speed sensor to limit the vehicles top speed by cutting the injectors power
    I believe the injector circuit is 12v 30amp
     
    Last edited: Apr 2, 2010
  6. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    Sounds dangerous, what would happen if you need to pass?
     
  7. higgy

    Thread Starter New Member

    Sep 5, 2009
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    It is an off road vehicle with a federal mandate to not exceed 25mph
    The idea is to use this type of circuit so that you have full power at anything below the 25mph restriction
     
  8. retched

    AAC Fanatic!

    Dec 5, 2009
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    The typical way to 'govern' vehicles speeds are to use the transmission. You know at which RPM in each gear that the vehicle reaches 25MPH. So you can use the hall effect sensor as a tach on the flywheel with an input from the transmission to restrict speed.
     
  9. higgy

    Thread Starter New Member

    Sep 5, 2009
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    The hall effect sensor for the speedo is on the trans output shaft. I want to use the signal from this sensor to switch a relay for the injector driver circuit on and off at 25mph. Off above 25mph and on at anything below 25mph.Now I could remap the ecm to provide this function but I have neither the time nor the inclination to "crack" the current ecm code. So I am thinking I need some sort of amplifier for the Hall effects sensor to be able to switch a 12 volt relay installed in line with the power source for the injector driver but I have no idea how to go about this. If someone could point me in the proper direction I would appreciate it immensely. Thx
    PS in the past this has been accomplished by welding restrictor plates on the trans to prevent 3rd and 4th gear operation. I think this is a silly idea and difficult to do on an automatic. Limiting speed with a relay for the injectors will work on either a manual or automatic and would allow normal engine and trans operation below 25mph. This would also eliminate the need for welding plates on every trans. Seems to me it would be a cheap add on regardless of vehicle setup.It will also have the added bonus of not affecting the engines emissions.
     
  10. retched

    AAC Fanatic!

    Dec 5, 2009
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    You can use an Op-amp to amplify the signal from the hall effect sensor, but you will most likely want to measure that signal with a uC and than have the uC trigger the relay. You can use a Darlington to get the amplification to energize the relay coil. It is dependent on the relay coil specs.
     
  11. higgy

    Thread Starter New Member

    Sep 5, 2009
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    I understand op-amp and Darlington pair What is a uC?
     
  12. retched

    AAC Fanatic!

    Dec 5, 2009
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    Micro Controller
     
  13. higgy

    Thread Starter New Member

    Sep 5, 2009
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    As in IC ? So once I find the output of the hall effect sensor at 25mph I can just find a suitable available chip and relay to do the job. I like that idea best. Thank you
     
  14. higgy

    Thread Starter New Member

    Sep 5, 2009
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    One more question if I may
    Do these hall effect IC's( two switches on a chip) have the power to switch a relay?
     
  15. BMorse

    Senior Member

    Sep 26, 2009
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    Does this hall effect sensor have an analog output proportional to the speed?

    B. Morse
     
  16. higgy

    Thread Starter New Member

    Sep 5, 2009
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    Yes,signal is proportional analog depending on the output shaft speed
     
  17. BMorse

    Senior Member

    Sep 26, 2009
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    So you will need some sort of circuit that can be triggered at certain levels of output.... it looks like you will have to devise an comparator circuit that you can adjust a "high" and "low" trip points.... you can then use the output of the comparator to switch a transistor which in turn can switch a relay load....


    My .02

    B. Morse
     
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