Summing Amplifier once Input is the Rail

Discussion in 'General Electronics Chat' started by Solstice, May 22, 2014.

  1. Solstice

    Thread Starter New Member

    May 22, 2014
    3
    0
    Respected All!
    I am not much into electronics and would like to ask a question, sorry if its too basic... I have two independent solar cell modules of same type which output 2-7Volts (with slight mvolt variation within both outputs) and i want to add both output voltages using a Summing Amplifier (like TI's LMC72xx). I need your kind guidance for:
    1... Can both inputs (outputs of solar cells) be add together provided if both are input to Summing Amplifier (IN+ and IN-), and, one of them is ALSO the Vcc to it? [Since, the circuit harvests power from solar cell, so, i only have output of Solar Cell as Vcc]
    2... If not possible, then any other topology like summing amplifier / solution which can be used in my application.

    Best Regards,
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,415
    3,354
    Why do you want to sum the voltages?

    If you wish to use two solar cells in order to increase the output voltage, simply connect them in series.
     
  3. djwilliams37

    New Member

    Dec 19, 2008
    4
    0
    Hi
    I agree same as connecting batteries together in series
     
  4. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    684
    92
    To me this seems likely intended for metering the output of his solar panels.

    Adding the voltages in series to get the power output does not require any type of amplifiers.

    The other possibility I will suppose comes from the OP maintaining that he does not know much about electronics. He may actually want a switching DC/DC converter. If he doesn't even know what that is from inexperience, then he may have connected what he wants in his mind with being some type of amplifier.
     
  5. Solstice

    Thread Starter New Member

    May 22, 2014
    3
    0
    Respected Sir!
    Thanks for your kind replies... I fully get it!
     
  6. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    684
    92
    You only needed to connect them in series, and your mind overcomplicated the solution?

    I have been there. Many times. Trust me on that.
     
  7. Solstice

    Thread Starter New Member

    May 22, 2014
    3
    0
    Respected Sir!

    In fact, the Solar modules are equipped with some sort of boost converter (as told me by one of my colleague, its some diodes sort of thing and else). The final output is given to a super-capacitor (150mF). I am in computer science department and my specialty is Operating Systems, thats why i got so confused in this.

    So, in my case, it means that i should
    (a) Combine two storage capacitors in parallel (for same voltage and more current capacity). I have checked the output portion of solar panels, and, there is a diode towards the end which means that both power supplies would remain isolated from the capacitor bank, if i am correct.
    (b) Combine two storage capacitors in series (for same current and more voltage capacity).
    I feel Sorry as i should have illustrated the whole scenario in the first post, and i should have studied little more.

    Thanks again for your kind responses!
     
  8. #12

    Expert

    Nov 30, 2010
    16,248
    6,745
    Backing up to the first post,

    The basic idea is flawed from this point of view: If one voltage is the supply for the amplifier, then the output of the amplifier can not output any voltage that is higher than the power supply voltage. Trying to sum two voltages together at the input to get a higher output voltage than the power supply for the amplifier can not happen.

    Nothing for you to do about this except understand why it won't work.
     
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