Newbie need help working with negative voltages

Discussion in 'The Projects Forum' started by ChrisChemist116, Jun 7, 2009.

  1. ChrisChemist116

    Thread Starter Active Member

    Mar 13, 2009
    these days i have been working in a project that requires +5V and -5V voltages. The IC in question is the intersil ICL7107.

    In the beginning i didn't know how to plug the wires to each battery so i could drive out the desired voltage. On my first two attempts, i accidentally blown two tantalum capacitors (2.2uF) on the LM7905 input. After reviewing my books, i came to the conclusion that i have been working with reverse polarity and i also accidentally misunderstood the pinout as my decision was to work with LM7805 and LM7905 and these two have different pinouts.

    Okay, the question is this:

    Is my schematic correct?. (PDF attached). Is that the correct way to drive out +5V and -5V from two 9V batteries.
    Help will be graciously welcome

    pd. Sorry for the graphics quality i didn't had time to make the schematic on the computer.
  2. haran

    Active Member

    Apr 6, 2008
    i tried out your circuit using multisim 10. but the negatif terminal doesnt seems to be given off -5 volts.
    do go to this website to check out their idea on how to generate a -5 volt
  3. eblc1388

    Senior Member

    Nov 28, 2008
    It doesn't need a circuit simulation to tell if the circuit is connected correctly. In this case, the simulation result is totally wrong. :mad:

    One additional point regarding tantalum capacitor.

    These capacitors are marked with a dot or a dark/black line near one pin. This is the positive +ve connection. Countless people have applied the marking convention of normal electrolytic capacitor and blown up their tantalum caps.

    Yes. Do yourself a favor. Always put in the polarity marking on a cap so it is easy to see if mistake is made when checking the circuit later.

  4. haran

    Active Member

    Apr 6, 2008
    as i said b4 through the simulation i got the positive 5v...but unable to generate the -5 volts...and i do noe how to read schematics tq..if u have multisim 10 i willl gladly send the simulation file