Homemade LM317 Bench Power Supply

Intro: Homemade LM317 Bench Power Supply

This is my first real project in electronics! I started by looking at the schematic and scratching my head a lot then just went for it!

I put the bits and bobs on the board and soldered them into place, wasn't really sure how or where to put the bits. Then i started soldering the wires as in the schematic that's easier said than done! after a few hours things started to come together, i finished the board and tested and to my amazement the psu worked! i would like to show afew pics and the schematic i used.

Comments

[sprasanna3]

Hi

I have a problem,after giving all the connections as per the diagram,the output voltage has only a minor difference(+/-2-6) even is the variable resistor is adjusted.

Any idea what may be the problem?

[Hammerhead46]

VERY NICE JOB!

I notice on the schematic your note " DO NOT CONNECT THE GROUND OF THE AC POWER TO THE COMMON OF THE POWER SUPPLY" .

Looking at the photos I do not see that ground wire at all.

I would connect the AC ground to the case of the power transformer, so that if the transformer should ever short out internally you would not have a hot transformer when servicing.

Also I do not see the 0.5A fuse shown in the schematic mounted anywhere, this I would always recommend be mounted to a externally (See Photo) accessible fuse holder with the center connector connected to AC HOT and side connector to transformer.

That way you cannot come in contact with the HOT AC while changing the fuse.

[joshuam511]

Sorry, just to be clear, can you just replace the Lm317 with and Lm350 with out changing anything else or would it change the range or voltages or anything? Thanks :)

[Bio961]

Can I use a 24v transformer without changing scheme ?

[GamerM]

Now i'd rather use Lm350.
Cause it gives max 3 Amps.
LM317 has max of 1.5 Amps.
And yes you can use 24V with no problems.
Just make sure you use a cooler.

[pfred2]

You look like you're off to a great start to me. Even if you're just building a circuit on perfboard I find it helps to model the circuit first in board design software. It makes the final build go a lot easier, and come out better for me too. Easier to play around on the computer, than with a soldering iron.

Your first supply came out a lot better than my first one did. When I made mine there weren't any personal computers though, so I guess I get a little slack there.

[Lectric Wizard]

Actually for something like a drill ,you don't need a regulator. If you use a 12v transformer all you have to do is rectify it with a bridge & add a capacitor to smooth it a bit & it will be happy. Drills under load take a lot of current , probably in the 10-15 A range. A good place to get high current transformers cheap is to get an old UPS, used for computer backup power & remove the step-up transformer. Wire it so the output side is now the primary & you have a great low voltage source. Usually they are within a couple of volts of what the battery voltage of the UPS was. i.e. 12v battery = 11v to14v ac . Current is roughly wattage of UPS / battery voltage. 300W/12v = 25A I have a bunch of these beasts around home & work , great for brute force power..

[Wizzkid1984]

Thank you for the info i should have thought of that myself! i have in the past cracked open a few dc adapters just to see what was in them and there just an ac transformer and a four 1N4001 diodes and a cap

[Lectric Wizard]

Welcome to the world of electronics !!! PSs are the best place to start, you get a lot of the basics without being overwhelmed. Nice clean job for your first project. If you need info feel free to ask. A lot of us here have been into electronics for a long time & love to share what we've learned.(45 years myself ) Yes, started when I was 4 years old... NOT !! CHEERS!!!

[Wizzkid1984]

Thanks, i got another project that i thinking about its converting a drill battery pack so that you can use a ac mains transformer (In its own housing) ive picked the LM338 Vreg witch in rated a 5A. I mainly use my drill at my bench and dont really need the battery, but its nice to have the best of both worlds. I was thinking build a 12V supply into the spare battery pack and use a DC Jack to input the ac. Do you think 5A will be enough? i had it running of a 2.5A PSU but once load was put onto the drill it was not very good