Newbie need help working with negative voltages

Thread Starter

ChrisChemist116

Joined Mar 13, 2009
79
Hi,
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.
 

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haran

Joined Apr 6, 2008
42
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

http://www.elecfree.com/electronic/generating-5-volts-from-a-9-volt-battery-with-ic-555/
 

eblc1388

Joined Nov 28, 2008
1,542
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:

On my first two attempts, i accidentally blown two tantalum capacitors (2.2uF) on the LM7905 input.
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.

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

 

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haran

Joined Apr 6, 2008
42
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
 
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