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Voltage sensing for switching accessories

Discussion in 'Power Electronics' started by PhilN, Jul 13, 2021.

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  1. PhilN

    PhilN

    10
    1
    Jul 13, 2021
    Hi there,
    As per my intro' message, I 've not been on the tools so to speak for a while but have a project I am hoping you can guide me on. But apologies if this is inappropriate here.
    I play about with old motorcycles and do some silly long distance rallies and time trials but the charging systems are usually the biggest headache.
    I am looking to build an accessory fusebox that is only live once the alternator voltage is present. So if the battery fully charged is say 12-12.4Vdc I want to integrate a voltage sensing circuit that switches power to the fuse box once the alternator is delivering a 14V output (say anything above 13V) will switch power to the fusebox.
    I've found various options for switching at a certain point below 12V but not above it.
    Anyone want to give me a start?
    Cheers
    Phil
     
  2. Bluejets

    Bluejets

    4,875
    1,018
    Oct 5, 2014
    You could use a transistor driven relay with a reference zener or a 555 circuit that will sense above say 13V.

    Just one example here but there are many.
    With the relay output you can pick whether the output contacts feed or cut off a load when the relay is either on or off.

    The logic might be a-about for your application but you'll get the idea.





    And then there is this which might be a better solution for you........

    https://circuits-diy.com/low-battery-voltage-cut-off-or-disconnect/
     
    Last edited: Jul 14, 2021
    PhilN likes this.
  3. PhilN

    PhilN

    10
    1
    Jul 13, 2021
    Thanks for this, the second link looks exactly what I was looking for, will know up a breadboard prototype
     
  4. Bluejets

    Bluejets

    4,875
    1,018
    Oct 5, 2014
    Could probably use an LM393 in place of the TL071 also....might be more available.
     
    PhilN likes this.
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