thoughts for a latching circuit

Discussion in 'The Projects Forum' started by nmc240, Apr 9, 2010.

  1. nmc240

    Thread Starter New Member

    Mar 12, 2010
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    I have a sensor that gives a signal that varies from 0-4.5V the sensor is powered by 12 volts. The question I have is how do I get the signal to latch and hold at 4.5V once it has reached 4.5V, until there is a power off?

    Any help would be appreciated.
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    1. Low power SCR, [ 2N5060 ], needs inverting to have a high output.
    2. Flip-flop
    3 Latching relay with driver
    4. Dual input optical coupler
    5. ?
     
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Some sort of analog, comparator-triggered, sample-and-hold

    Maybe a PIC with an ADC input and a DAC (PWM/low pass filter) output.


    Ken
     
  4. sgardner025

    Active Member

    Nov 5, 2009
    79
    4
    Maybe a latching comparator IC.
     
  5. nmc240

    Thread Starter New Member

    Mar 12, 2010
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    Sorry for the long time between replies, I was out of town over the weekend. I have looked at all of the ideas and one thing I noticed was that there was no cheap way to do it. Is there a cheap way to do this?

    Thanks
     
  6. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Can you elaborate? Is this an automotive project? Does the sensor voltage drop below 4.5v after it reaches that value?

    Ken
     
  7. nmc240

    Thread Starter New Member

    Mar 12, 2010
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    Yes this is an automotive project. The signal I need to latch goes from 0-4.5V depending on the pressure is applied to the gas pedal.
     
  8. rjenkins

    AAC Fanatic!

    Nov 6, 2005
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    Sorry, the forum policy does not allow projects that could affect vehicle safety & connecting in to the throttle control is a very hazardous thing to do.
     
  9. nmc240

    Thread Starter New Member

    Mar 12, 2010
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    It actually doesnt attach to the throttle. I used a IR LED and Poximity sensor to measure the distance from the pedal to the floor.
     
    Last edited: Apr 12, 2010
  10. nmc240

    Thread Starter New Member

    Mar 12, 2010
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    Kinda changed directions alittle bit, Just wondering if this looks like a viable option for peak and hold.

    Would this make the signal stay at the highest level that it reached until the switch was closed?
     
  11. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Yes...for a while. The capacitor will slowly discharge.

    Ken
     
  12. nmc240

    Thread Starter New Member

    Mar 12, 2010
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    What would be a good op amp to use for this i tried a lm358 but it is not working at all for me?
     
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