15VAC Dual adjustable regulated PSU 5V-25VDC

[fader08]

Is this Design is right?? I'm just getting 5V-20VDC..
how could I make it 5V-25VDC?? please help me.. thanks.

 

[fader08]

can someone pls. help me??? thanks

 

[Elvee]

It is a very poor design, you should use the LM317/337 pair.
Anyway, if you want to go higher with this one, you should use pots of higher value, or connect a resistor (~22K) between the common and output of the regs

 

[sofaspud]

±25 volts output is overly generous from a 30VCT transformer. You need a transformer with a higher secondary voltage.

 

[fader08]

Is this Design is right?? I'm just getting 5V-20VDC..
how could I make it 5V-25VDC?? please help me.. thanks.

It is a very poor design, you should use the LM317/337 pair.
Anyway, if you want to go higher with this one, you should use pots of higher value, or connect a resistor (~22K) between the common and output of the regs

hey,, can I know what you mean with "regs"? sorry not a familiar term. thnks.

 

[sofaspud]

"Reg" is short for regulator.

 

[fader08]

Thnks for the rply sofaspud, but even evlee's comment didn't work., still 5V-20VDC.,
is there any other solution to make it to 25VDC??

 

[fader08]

"Reg" is short for regulator.

thanks for your rply., bur even elvee's comment didn't work still i get 5V-20VDC.,
is there any other solutions you can help?? thanks.

 

[AndrewT]

add a second bridge rectifier.
Use the whole 30Vac as input and you get ~45Vdc at the smoothing capacitors.

DO NOT connect the ground of the second supply to the ground of the first supply.

 

[fader08]

add a second bridge rectifier.
Use the whole 30Vac as input and you get ~45Vdc at the smoothing capacitors.

DO NOT connect the ground of the second supply to the ground of the first supply.

what do you mean by this?

 

[sofaspud]

is there any other solution to make it to 25VDC??

You need a transformer with a higher secondary voltage.

Use a bigger transformer, 18-0-18 to 24-0-24. Then use the resistor tweaks from Elvee's post if need be.

 

[Elvee]

Use a bigger transformer, 18-0-18 to 24-0-24. Then use the resistor tweaks from Elvee's post if need be.

Yeah, but then it is probably better to start from completely fresh and healthy bases, get rid of this awful regulator and use decent 317/337 as regulators.
They could be as much as ten cents more expensive apiece, but they are worth every additional cent and more compared to the 7805.
In addition, the minimum voltage will be 1.25V, which is useful to emulate single cell supplies that are becoming increasingly common these days