0-30vdc variable powersupply?

[Ian]

Hi
i would like to build a 0-30v DC variable power supply. it could be like 1.5v or 2.5v to 28v or 25v or 29v so basically what i am saying is that it does not have to go down to 0v and does not have to go all the way to 30v. I would also like it to have between 2.5a and 3.5a of of current. Also i would like it to have a maximum current output control so i can control the maximum current output. So i need a tutorial or a kit for this project.

[Jon Chandler]

Here's a way I made an adjustable power supply meeting some of your needs:

Ten Buck Lab-Grade Variable Power Supply

It uses an LM317 to regulate the output from a higher-voltage wall-wart switching power supply.  It will handle up to about an amp depending on the voltage drop across it and has no current limiting but it's a easy starting point.

[Ian]

Thanks thats cool. Ya i have something like that

[Zero999]

Yes, the LM317 is good for this but it's only rated to 1.5A, if you want more you'll need additional components.

To cut down on power dissipation I'd recommend using a centre tapped transformer and switching to the centre tap for lower voltages; this can be done automatically if needs be.

The minimum output voltage from the LM317 is 1.25V, to go lower you need additional components.

[Hypernova]

Look up TI's OPA54x series opamps that can deliver up to 10A from up to 80V, TI actually include example on how to make pot or DAC programmable PSUs out of them.

[grenert]

For a beginner, the LM317 is nice in that it has built-in short-circuit protection.

[Ian]

thanks so much