Increasing current problem

Discussion in 'General Electronics Chat' started by jeffmeier, Oct 12, 2011.

  1. jeffmeier

    Thread Starter New Member

    Oct 12, 2011
    I am trying to increase the output current from 4 x 3.6V solar cells to that which will trigger a 555 timer. Presently I am only getting a maximum output from the cells of 20 micro amps. How can I increase this current?
  2. SgtWookie


    Jul 17, 2007
    Try taking the cells outside when the sun is shining.
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
    I hope this is about detecting dim light rather than some over-unity hogwash. Solar cells are not ideal for detecting weak light. The level may be pretty temperature dependent unless it is held well down by a low impedance load (the Maximum Power Point voltage gets very low, and you need to keep below it for a reasonably stable and linear response). That might get in the way of using the cells to generate power in brighter conditions.

    Some other detector like a medium-sized photo-diode, a photo-transistor or a CdS photoresistor may be a better bet.

    That said, you may be interested in the cell output, temperature dependency and all, if what you are trying to detect is the beginning of useful output from the cells. In this case, for a valid result the cell must deliver a voltage approximating the required load voltage, either into a the real load, or a dummy. 20μA does not sound very much, but should be plenty enough to drive an op-amp or even to trigger a comparator directly. Their output can trigger the 555.
  4. wmodavis

    Well-Known Member

    Oct 23, 2010
    To get maximum current from a solar array the plane of the array should be perpendicular to and in full exposure to direct sunlight. Be sure none of the cells are even partially shaded.
  5. dataman19


    Dec 26, 2009
    Increase Current? Solar Cell Current?????
    Get more solar cells...
    Seriously. Those cells may put out 3.6V at 20mA. But they will put out only about .55V at 30-60mA (such is the nature of solar cells). So you need more solar cells.... Pure physics and fact....
  6. Adjuster

    Well-Known Member

    Dec 26, 2010
    The OP said 20 microamps! Such low currents really do suggest operation indoors. I have just tried a solar charger in my rather dimly lit living room (it's night here). Normal output is up to 50mA into 15V in UK sunshine. Right now it makes only 10.3V into 10MΩ, or 27μA into a low resistance.

    All very interesting, but if the OP has no more to say...