Need to understand the functioning of this circuit.It is Charge controller..

Discussion in 'The Projects Forum' started by corefinder, Oct 18, 2012.

  1. corefinder

    Thread Starter Member

    Oct 6, 2011
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    I couldn't find out any 8051 based solar charge controller. Finally,i came up with this circuit.:) But i am not able to understand its functioning.:confused: Although I now the basic understanding of the circuit but not able to understand the functioning of certain components placed in it. like this optocoupler wht its doing there and this BC547, dont know how its working.
    Now, in whole summary i am making a solar lantern, so this is a charge controller. why i am using this circuit if am a newbie is because i know the architecture of 8051 microcontroller so i found only this circuit on net. I have bigger challenges i need to design PCB according to the circuit toooo:eek:. I need a lot help from you guys. Help me..:(
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The function can only be found with the program of the 8051.
    Without the program, you will not know what it is doing.

    Bertus
     
  3. corefinder

    Thread Starter Member

    Oct 6, 2011
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    Yes, I tried to understand its working using the code but failed. I have attached the given code.
     
  4. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Is there no explanation on the site where you have found the circuit?
    The bc547 is there to detect if the solar cell is producing enough voltage to charge.
    The opto coupler is there to switch the load.

    Bertus
     
  5. corefinder

    Thread Starter Member

    Oct 6, 2011
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    Thanks Bertus, for taking some time. Although there is no explanation given on the site. I appreciate your help :)
     
  6. corefinder

    Thread Starter Member

    Oct 6, 2011
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    Hey, I wanted to know how BS170 is working in the circuit mentioned before and can anyone provide me the link to its datasheet. Google is showing different kind of BS170 and i am confused which one is used here.
     
  7. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The BS170 is a small mosfet, that is switching the relays.
    The relays connects the solar cell to the battery.

    I have attached the datasheet for the BS170.

    Bertus
     
  8. evilclem

    Member

    Dec 20, 2011
    118
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    I'm more interested in what T1 (BC547) is supposed to achieve. As far as I can tell it simply adds a 500 micro-amp load to the 5V rail when the solar panel is open circuit (switched off the battery), but I don't understand why.
     
  9. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    As you can see there is a zener diode in series with the base of the BC547.
    The transistor will be activated when the voltage of the solar cell is above the 16.2 Volts.
    A voltage divider of two equal resistors => (2* (7.5+0.7)) = 16.2

    Bertus
     
  10. corefinder

    Thread Starter Member

    Oct 6, 2011
    55
    0
    Thanks for providing the data sheet. Actually want to know little bit more that how this mosfet is performing switching. Initially i think its open but as battery is charged the P3.5 is giving a signal to gate and its closing the connection but then in which direction current will flow so that relay turns into open state.
     
  11. evilclem

    Member

    Dec 20, 2011
    118
    16
    Hi Bertus,

    I worked that bit out but am having trouble as to why the transistor needs to activate for a high solar panel voltage.
     
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