5V battery switchover circuit

Discussion in 'The Projects Forum' started by gtcreate, Feb 23, 2010.

  1. gtcreate

    Thread Starter New Member

    Feb 23, 2010
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    Hi all,
    New to the forum, and rusty in circuit design. I'm tasked with adding a backup battery and switchover circuit to a system that currently runs off 3 D-cell alkalines.
    1. The circuit needs to be modified to run off the main 3-Dcell pack until voltage drains to below 4V.
    2. At this point it needs to switch to the secondary 3-AA cell pack until drained.
    3. The current system draws only 5mA to a max of 150 mA, and is required to run for several months of constant sampling. This means my new circuit must be a very small additional load.
    4. The circuit must "seamlessly" switch batteries.

    I've attempted using a TPS2112 for this, and can supply the schematic if needed, but this seems to be an un-ideal candidate. Firstly, I don't want the batteries oscillating back and forth. Secondly, the circuit does not seem to switch seamlessly enough. The voltage drop upon switch seems to cause the system to glitch. I'm hoping for any assistance/advice or best yet a diagram.
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    That part is perfect as far as I can see. I think you need to recheck the circuit you are building. Post it so that we can see what might be wrong with it
     
  3. gtcreate

    Thread Starter New Member

    Feb 23, 2010
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    I'm posting the circuit. The first question I'd like to resolve is how do I ensure that the primary battery is not used again once the secondary source drains? I want the primary battery to essentially disconnect as soon as it falls below 4V.
    I've got the 2110 used in this schematic, but I don't see any reason the 2112 and 2110 wouldn't be interchangeable.
     
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Did you read the Data sheet thoroughly
    It's important that you understand the data.
     
  5. gtcreate

    Thread Starter New Member

    Feb 23, 2010
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    quite honestly the data sheet is overwhelming me a little bit. I'm not familiar with the hysteresis issues, and I'm not sure how to prevent the yo-yo effect that occurs once the batteries have both drained to 4V, or in the case that the primary self-charges enough to get over the 4V threshold.
     
  6. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    OK then, I'll need a little time to study the circuit and specs, as you know I'm helping other and tutoring via the net takes a bit of time and as I have other chores to do.
    I hope you have patient or is this one of the limited time project
     
  7. t06afre

    AAC Fanatic!

    May 11, 2009
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    Yes reading the data sheet AND understand what is says is important. I remember for a while ago a member from the Maldives wanted some help to program a RAM chip, that he was sure was a microcontroller
     
    Last edited: Feb 25, 2010
  8. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    :rolleyes: OK!!! OK.. I was careless .. I admit...
    Stop pulling my leg...will ya!!!
     
  9. t06afre

    AAC Fanatic!

    May 11, 2009
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    For the moment I shall do my best. But the story is far to good to be completely forgotten:p
     
  10. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    you guys won't let go.. wouldn't u? huh !!!;)
     
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