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Will this circuit work?

Discussion in 'Electronic Basics' started by smpaladin, Sep 26, 2004.

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  1. smpaladin

    smpaladin Guest

    This is what the above circuit is supposed to accomplish: As long as
    a magnet is held above the hall sensor, it will turn on the coil. It
    does that by utilizing a power transistor.

    Will this setup work properly? Will it work properly if up to ten of
    these circuits are connected to eachother and how much battery power
    would I need to run it?
  2. John Fields

    John Fields Guest

    I won't run properly unless you connect the coil between the collector
    of the transistor and battery + and connect a diode across the coil
    with the cathode of the diode going to battery + and connect the
    emitter of the transistor to battery -. It also won't work properly
    if you don't have enough current coming out of the Hall sensor, and
    you may toast the transistor if you don't put a resistor between the
    output of the Hall sensor and the base of the transistor.

    As for the rest of it, until you can more clearly describe what the
    parts look like, electrically, and what you really want to do, you're
    just pissing in the wind.
  3. CFoley1064

    CFoley1064 Guest

    Subject: Will this circuit work?
    Hi, Paladin. There are many types of Hall Effect sensors, and you're not too
    specific about which one you're using, so I can't say for sure. However...

    Many hall effect sensors are made with "open collector" output. That means
    that, when they're on, their output pin will sink a few mA of current from a
    pullup resistor or other source.

    If you've got a type like that, you might want to try using a PNP transistor
    and try something like this (view in fixed font or M$ Notepad):

    | | | |
    | | | |
    | | | |
    | | .-. |
    | .----o---. R| | |
    | | + | | | |
    | | | '-' |
    | | Hall | ___ | |<
    | | Effect o----|___|-o--|
    --- | Sensor | R |\
    - | | |
    | | | .---o
    | | - | | |
    | '----o---' | |
    | | | C|
    | | - C|
    | | ^ C|
    | | | |
    created by Andy´s ASCII-Circuit v1.24.140803 Beta

    Choose R such that about 1/10th of the current required by the relay coil will
    be drawn by the base (note that many of these hall effect sensors are limited
    to about -20 mA output current, so keep that in mind).

    I hope this works for you. Be sure to check your sensor to check the specs.
    If you're not sure, feel free to post again with more information. Battery
    voltage, relay coil resistance, sensor type would all be helpful.

    Good luck
  4. "It's all coming back to me now", said the blind man as he peed into the

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