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Help with Sensor — Parallax Forums

Help with Sensor

ManuelManuel Posts: 105
edited 2005-08-02 21:25 in General Discussion
Hello:
Due to the delivery time of my Mexico distributor of parallax products and the need of soon delivery of my project i was forced to buy a alegro microsystems linear hall effect sensor 3516 (Diagram http://www.allegromicro.com/sf/3515/·). I would appreciate if anyone could help me develop the necessary circuitry to connect the sensor to my BS2sx, I only need to read 1s and 0s. If i succeed with the project ill be making·some more but with the melexis sensor.
Everything to help me will be warmly welcome

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Best Regards

Manuel C. Reinhard

Comments

  • YanroyYanroy Posts: 96
    edited 2005-08-02 18:52
    Buy a standard op-amp (or perhaps even something that's intended to be a comparator) and use it as a comparator.· Do this by attaching the output from your hall sensor to the + input on the op amp and the wiper from a pot to the - input.· The other two pins on the pot should go to your positive and ground rails.· Adjust the pot until the output fromt the opamp/comparator is 1 when you're in the desired state and 0 otherwise (or vice versa).· What is happening is the op-amp is comparing the two input voltages, so by adjusting the pot, you're setting the threshold at which the output switches from 0 to 1.· I hope this helps; more info on your intended use could help us figure out what you're trying to do.
  • ManuelManuel Posts: 105
    edited 2005-08-02 19:34
    could a A/D converter work? or could i just read it with the stamp like a switch?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Best Regards

    Manuel C. Reinhard
  • YanroyYanroy Posts: 96
    edited 2005-08-02 19:52
    An A/D should work fine.· It won't give you 1's and 0's, so you'll have to set a threshold in software.· Setting it up like a switch won't work unless you have some way of setting a threshold (or if you're lucky enough so whatever you're trying to detect with the sensor causes the output to swing above/below 1.4V, the stamp's internal logic threshold).· If you're very clever, you might be able to work out a voltage divider and/or transistor to cause the signal to swing about the 1.4V point.· I recommend either the A/D or the opamp/comparator.
  • ManuelManuel Posts: 105
    edited 2005-08-02 20:13
    Another question, do you think that the ULN2803A could work for me as a switch? conecting the output of the sensor to the input of the ULN and the out of the ULN to a BS2 pin having a 5v voltage as the ULN supply.

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    Best Regards

    Manuel C. Reinhard
  • ManuelManuel Posts: 105
    edited 2005-08-02 21:25
    Yay, i made it work with the help of a NAND circuit to get 1 when a magnetic field is near and 0 when not.
    [noparse]:D[/noparse]

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Best Regards

    Manuel C. Reinhard
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