What does it mean when the voltage lower it self up?

[LegendBreath]

If you can't post a simple schematic then how can we help you?
I use Microsoft Paint to draw all my schematics. With the Shift key depressed, the mouse makes perfectly straight lines. It can copy and paste stuff from other schematics.
I copied and modified this tiny schematic and your circuit should be wired the same:

Yeah, that's what I realized so, I drew a schematic with ExpressSCH. Here it is:

That's EXATLY what I got...View attachment 37856

 

[audioguru2]

Look at the huge difference in the wiring of your circuit that doesn't work, and my circuit that works.
I don't know what is 1, 2, 3 terminals on your regulator so I copied its pic from its datasheet:

View attachment 37857

 

[LegendBreath]

Look at the huge difference in the wiring of your circuit that doesn't work, and my circuit that works.
I don't know what is 1, 2, 3 terminals on your regulator so I copied its pic from its datasheet:

1 = Input, 2 = Ground, 3 = Output

And, is there a big diff?

There's ONE thing that I really DON'T understand... on your schematic, the capacitor is on the +15.6 and the GND line... is it suppose to be like that? That's maybe why it's doesn't work!

 

[audioguru2]

A capacitor is designed to block DC current.

Your circuit has a capacitor blocking DC current from the rectifier to the regulator. My circuit has the positive terminal of the rectifier connected directly to the input of the regulator.

Your circuit has a capacitor blocking DC current from the negative terminal of the rectifier to the common. My circuit has the negative terminal of the rectifier connected directly to the common.

Your circuit doesn't have any filtering of the rectifier's output. Mine does.
You can't see the diff? It's a huge diff.

 

[LegendBreath]

A capacitor is designed to block DC current.

Your circuit has a capacitor blocking DC current from the rectifier to the regulator. My circuit has the positive terminal of the rectifier connected directly to the input of the regulator.

Your circuit has a capacitor blocking DC current from the negative terminal of the rectifier to the common. My circuit has the negative terminal of the rectifier connected directly to the common.

Your circuit doesn't have any filtering of the rectifier's output. Mine does.
You can't see the diff? It's a huge diff.

Mwhahhahahahhah THANKS! Thank you soo much! Now, I got 14.77VDC And, my 6v is not 5.5VDC now it's 6.05VDC Thanks! I will sleep much more intelligent tonight

DAMN! I'm gonna cry!!  :'( :'( Now I got the exact same problem that I started up with... is that because 4700uF is too much or not enough?

OMG!!! That capacitor just BLOWED in my face!!  The one for the 15.6VDC place. What happened!??! Ok, it not really blowed, the cap is just like liffed up and it made some smoke

 

[audioguru2]

You connected the capacitor backwards. Its negative wire is marked with a minus sign.
Replace it and connect the new one the right way around. The new capacitor should have a 25V rating.

Don't forget that the 7806 needs at least an 8.5V input, so the 6VAC when rectified and filtered is too low for it.

 

[LegendBreath]

Don't forget that the 7806 needs at least an 8.5V input, so the 6VAC when rectified and filtered is too low for it.

Oh yeah? Well, it's working really fine for me...  ???

 

[Alun]

audioguru,
LegendBreath is using 7VAC on the input so 7*root(2) - 1.4 = 8.5, I think the LM7806 will output 6V fine afterall.

 

[audioguru2]

Hi Alun,
Thanks, I was calculating for 6VAC in error. :-[
Actually, his 7VAC will probably be much higher unless he is overloading the transformer or operating it at its limit.

You know what? I bet it is a 5VAC winding when loaded, but he measures 7V without a load.
Then the DC input to the regulator will be less than its output voltage. A miracle. ;D

 

[LegendBreath]

Hi Alun,
Thanks, I was calculating for 6VAC in error. :-[
Actually, his 7VAC will probably be much higher unless he is overloading the transformer or operating it at its limit.

You know what? I bet it is a 5VAC winding when loaded, but he measures 7V without a load.
Then the DC input to the regulator will be less than its output voltage. A miracle. ;D

Geez... you are really confusing me guys!

 

[Alun]

What does it say on the transformer's packaging?

A 5V transformer might give a higher voltage like 7V when nothing's conntected to it, but 5V when a load equal to its current rating is. This is because the transformer its self has an internal resistance. This problem is generally wors with smaller transformers because they're made with thinner wire and therefore have a higher internal resistance.

 

[LegendBreath]

What does it say on the transformer's packaging?

A 5V transformer might give a higher voltage like 7V when nothing's conntected to it, but 5V when a load equal to its current rating is. This is because the transformer its self has an internal resistance. This problem is generally wors with smaller transformers because they're made with thinner wire and therefore have a higher internal resistance.

It's a big transformer taken from a stereo (amplified stereo) it's about 2x2x2inches.

 

[Alun]

That explains why it has a 7V output often stereos have weird voltage transformers but there again I can'be sure it's not a 6.3V output unloaded.

 

[audioguru2]

Why is a little 2"x 2"x 2" transformer considered to be "big"?
Was it from a 2W boom-box stereo?
??? ???

 

[Alun]

Good point audioguru, I normally think of thins in metric and 2" is only 51mm, this is quite small for a transformer. I would think that the load regulation of a small transformer like the is quite poor so output voltage will drop quite a bit when a load is connected.

 

[LegendBreath]

Ok... sorry, cuz for me, it's one of the biggest transformer I got here  :

 

[audioguru2]

Hi LegendBreath,
How much current is your regulated 6VDC output going to supply? What is its load?
We are afraid that your big, little transformer can't supply enough current without its output voltage dropping too low. Also it might overheat if it is overloaded.

The regulated 6V output might also drop when the 12VAC is loaded.
The 12VAC will drop when the regulated 6VDC is loaded.

 

[LegendBreath]

How can I know what it will give me when it's loaded ???

And BTW: Here is some pictures of my "crappy" project





BTW: I don't have my 12V regulator for now...

 

[audioguru2]

Hi LegendBreath,
You project isn't crappy, but your transformer might be.
What is the voltage at the input to the regulator without a load?

If you have three 47 ohm/1W resistors, connect them in parallel across the output of the regulator as a load, then measure the input and output DC voltage of the regulator. Don't leave them connected too long or they will get hot and the transformer might get hot too.

 

[LegendBreath]

Hi LegendBreath,
You project isn't crappy, but your transformer might be.
What is the voltage at the input to the regulator without a load?

If you have three 47 ohm/1W resistors, connect them in parallel across the output of the regulator as a load, then measure the input and output DC voltage of the regulator. Don't leave them connected too long or they will get hot and the transformer might get hot too.

Ok thanks audioguru,
I'll try to find some 47 ohm resistors. And, without the load it is 7VAC and 12VAC.