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voltage triggered switching

Discussion in 'General Electronics Discussion' started by RobSmith, Jan 18, 2012.

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  1. RobSmith


    Dec 16, 2011
    Hi All,

    I am still working on my Stirling engine powered off grid setup.
    My battery pack is 48v 450ah and I am working my way through how to control the stirling engine and charging 'regime'

    I have scrawled all over a piece of paper the plan of how things will funtion and interact. The good thing is I will not have any instant feedback loops as the huge battery pack will not allow the voltage to be changed quickly which helps simplify my plan.

    The first item will be a 'voltage triggered switch'. This needs to spot when the battery pack drops below about 51.5v to kick things into life. Its input might want some capacitors or something to soak up odd spikes that might cause a false trigger or a timer setup that looks again to see if the conditions are still the same.

    I will also need to make a latching version of this that latches when the voltage reaches about 57v to switch on the current watching circuit.

    I will create a 0v / 12v power supply for the simple electronics to run from.

    Can anyone give me some pointers as to what devices can monitor a voltage around 40 to 60v and give an output when a threshhold is reached. I used the LM339 comparators years ago in a smiliar way but only down at a few volts.

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Hi Rob,
    the LM339 is good for the job. Build a Schmitt-Trigger with some hysteresis to avoid flickering action around the treshold.
    Since the LM339 is not good for 50 V, just scale down the battery voltage by 10 (resistive divider) and set the threshold to 5.7 V instead.

  3. RobSmith


    Dec 16, 2011
    Thanks for that.
    I think that is what I may end up doing.

    I am looking at getting a few of these: TL783CKCSE3 to provide me with a 12v source to work with.
    Also looking at LM2576 mentioned in a previous post.

    Last edited: Jan 18, 2012
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