Voltage Controlled Switch

Discussion in 'The Projects Forum' started by brighteyes, Dec 29, 2009.

  1. brighteyes

    Thread Starter New Member

    Dec 29, 2009
    4
    0
    Guys

    Was wondering if someone could help me with a small project.

    I'm after something that will allow me to control (open or close) an output based on an input voltage taken from a Gear Position sensor on a motorcycle (0v to 5v) i.e. neutal=0.5v, 1st=1.1v, 2nd=2v, 3rd=2.7v, 4th=3.5v, 5th=4.1v and 6th=4.7v)
    Otherwards turn on when voltage is between 0V and 3V and off up to 5V.
    (On for 1st, 2nd & 3rd and off on 4th, 5th and 6th)

    I'm a bit rusty but something tells me I simply need a zener diode to allow a voltage connected to an operational amplifer?

    Also, what if I wanted to switch the output on for 4th i.e. variable resistance?

    Thanks

    Pete
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    You can use a comparator circuit with an op amp and a pot to adjust it at what gear (voltage) the comparator will output high.
     
  3. brighteyes

    Thread Starter New Member

    Dec 29, 2009
    4
    0
    Thanks buddy

    Is it possible to purchase these off the shelf?

    Regards
    Pete
     
  4. mik3

    Senior Member

    Feb 4, 2008
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  5. brighteyes

    Thread Starter New Member

    Dec 29, 2009
    4
    0
    Thanks Mik3

    Very helpful information.
    Pete
     
  6. brighteyes

    Thread Starter New Member

    Dec 29, 2009
    4
    0
    Mik3

    I assume it works by comparing the voltage and then producing an output voltage itself? Or will it simply open and close a circuit as an output?
    I need the output of the circuit to close a circuit like a relay? I was planning to connect this device between the signal wire etc

    Thanks

    Pete
     
  7. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    You can activate a relay but the output current capacity of a comparator IC is not enough to drive a relay directly, thus you need to use a transistor to increase the output current capability of the IC.
     
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