Adjustable Power Supply

[HellasTechn]

Computer power supplies are great for this kind of thing. But what output voltage range do you need? Generally people use the +12V output, and you will be able to vary the voltage on that rail somewhat, but not over a very wide range. You should be able to drop it down to 8.6V and 3A won't be a problem.

It could be a problem because they are regulated. Once i tryed to do this on an old PSU and it would just shud down itsself probably because it detected output overload.

 

[HellasTechn]

A "12V 30A"

Wattage is voltage multiplied by current, so again it depends on the amount of current flowing.
True for DC (ac aint the same right ?)

So a 12V 30A power supply will not damage a cicuit that only draws 72W (6A).

The only case where a high-current power supply will damage a low-current load is when the power supply is not regulated, and its voltage is higher than it should be when it is not sufficiently loaded.
OHM's law .

 

[Arouse1973]

Thanks Steve. I think I'll order the LT1085, breadboard the circuit with the LM317 just to see if I can get it to work, then swap it out for the 1085 when it arrives. Thank you to everyone for your help.

Just be careful Fred on how much power you dissipate, I am not sure what current breadboards can handle.
Thanks
Adam

 

[FredF]

I will do that. Thanks. Just ordered four LT1085s for $4.28+$2.00 USD shipping. Should see them in less than a week. Just one quick question for Adam. In the schematic you posted for me, is the value of R1 actually 240Ω, or is it supposed to be 240K. To a rookie like me, that seemed kinda low. Just wanted to be sure. Take care all.

 

[Arouse1973]

Hi Fred 240 Ohm
Adam

 

[FredF]

Cool. Thanks.

 

[FredF]

Hey everyone,I'm back! Had some family health issues to deal with, but everything's o.k. now. Finally finished the adjustable power circuit,thanks to all who contributed their knowledge & expertise. I posted a couple pics of the finished product. Thanks again to all.
Fred