I hooked up my 5 volt regulator (LM2940CT) to a 9 volt battery, but for some reason the output voltage is 6.5(approx.). I checked everything but i couldn't find the problem, I also tried different regulators but I still had the same problem.
So if someone can tell me what might be the problem it would be great.

 

What is the full part number. Does it say, LM2940CT5.0? Or does it say LM2840CT9?

The LM2940 comes in various voltage output versions.

 

I said it was 5 volts

 

Did you connect a load to the regulator output?

 

I said it was 5 volts

That is awfully rude. Gopher is just trying to help and make sure you have the right part. What is wrong with providing the full part number that you are using? And a schematic for that matter?

And you never answered the question on a load. Are you measuring the supply with a load?

 

Yes a 130 ohm resistor which should be a big enough load according to the data sheet.

 

Sorry, I didn't mean to be rude.

 

Here is the data sheet link: http://pdf1.alldatasheet.com/datasheet-pdf/view/170572/NSC/LM2940CT.html

 

Do you have the capacitors connected?

A schematic would answer a number of questions without having to ask them...

 

Aren't capacitors needed just for smoothing out the voltage for frequency stuff ? (sorry if my questions are dumb)

 

Do you have the capacitors connected?

A schematic would answer a number of questions without having to ask them...

But does not answer if everything is wired correctly. Which should be checked, double checked, triple check and quadruple checked.

 

Here is the data sheet link: http://pdf1.alldatasheet.com/datasheet-pdf/view/170572/NSC/LM2940CT.html

That still doesn't tell us the exact part number of the one you have.

 

Aren't capacitors needed just for smoothing out the voltage for frequency stuff ? (sorry if my questions are dumb)

No. They also stabilize the device to prevent oscillations (which can appear as a change in voltage when measure with a DC meter).

 

Yes I checked a couple of times and I also changed the regulator and still I had the same problem.

 

All of these responses and still not letting us now the FULL PART NUMBER!

 

Yea, but don't you thing a 1.5 volt oscillation is a bit much

 

Lm2940ct-5.0

 

Carefully read the opening 3 paragraphs on Page 13 of the data sheet. They pretty well say it all.

 

All of these responses and still not letting us now the FULL PART NUMBER!

And no schematic. Two of the very first things that should have been posted.

 

I hooked up my 5 volt regulator (LM2940CT) to a 9 volt battery, but for some reason the output voltage is 6.5(approx.). I checked everything but i couldn't find the problem, I also tried different regulators but I still had the same problem.
So if someone can tell me what might be the problem it would be great.

The 2940 and 2941 series are notorious for oscillating if you don't have the right input and output capacitors. When they do, a DMM will read the wrong output voltage because there is an AC component and it is peak reading that along with the DC level.