P2P LM317 Power Supply CAD Layout (Tangent's Version)

[vksy]

Here is my draft CAD protoboard layout of Tangent's LM317 power supply (STEPS):

http://img.photobucket.com/albums/v3.../lm317_ps1.jpg

I designed this to complement another future P2P project - a tweaked Millett hybrid amp. It includes all suggested parts except generic bridge diodes which are cleaned by noise suppressor caps. There are no overlapping signals so the board can be wired entirely with bare tinned copper for that extra neat look. All component dimensions were taken directly from product specs. This layout fits perfectly on Radio Shack's 40 x 55 hole protoboard (PN #276-147). Cost of parts for the power supply runs about $45.

This is still a work in progress. Comments and/or suggestions on how the layout can be further improved are appreciated. Thanks!!


CAUTION
This is a "bare" P2P power supply project. It has not been built or tested. This is my pet project, and I am not peddling it for anyone else to use. I posted it for experienced builders to review and offer layout suggestions. If you decide to use it, take extreme care and do so at your own risk.

 

[individual6891]

What's wrong with tangent's version that's cheap and easily available?

I might be missing something here of course!

 

[vksy]

This is simply a P2P of Tangent's version of the LM317 power supply. I'm designing a tweaked P2P Millet hybrid amp and just wanted a P2P power supply to go with it. Please do not imply anything more than that.

BTW, I gave Tangent a courtesy email before posting this, and he gave me the green light.

 

[jerb]

may i ask what the output voltage is and is it adjustable?

 

[vksy]

The Millett hybrid amps needs around 28V, so that's what this psu is configured for. Tangent provides resistor (R3/R4) values in the schematic for use with a 500 ohm trim pot (VSET) that sets the LM317 (IC1) output voltage. The maximum is 35V.

 

[BrokenEnglish]

nice take, vksy! i'm sure, this will be a good psu. what's the diameter of your wiring?

Quote:

Originally Posted by jerb may i ask what the output voltage is and is it adjustable?

you could also recalculate the output voltage to your needs:
Vout = 1,25V * (1+ (R4+VSET)/R3)

 

[individual6891]

your Live line getting very close to the secondary side of the transformer.. though if you don't care about regulation then nevermind

heck it's p2p

 

[phobus]

This is very nice... I think I'm going to make the right side of that and use it with a wall transformer

 

[vksy]

Quote:

nice take, vksy! i'm sure, this will be a good psu. what's the diameter of your wiring?

Thanks! I plan to use 22 AWG from AC input to T1 primaries and then 24 AWG from T1 secondaries to DC output.

Quote:

You'll want your Live/Neutral/Earth pads to be bigger to allow for thicker wire.

The layout is scaled to perfectly match a drilled protoboard with 0.1 inch (2.54 mm) grid spacing. The pads serve as reference points only. The board's hole diameter is 0.042 inch (1.067 mm) which is pretty standard and fits most component leads. Aside from those mentioned, L1 (x4), T1 (x9), and HS1 (x2) also need to be enlarged.

Quote:

Also your Live line getting very close to the secondary side of the transformer.

Thanks for pointing that out because this project is bare P2P. I will make sure there's sufficient gap between signals in the actual build.

Quote:

I think I'm going to make the right side of that and use it with a wall transformer

That's a great way to cut cost, however, I have not built or tested this layout. Please proceed with caution if you decide to follow it. User beware.

 

[BrokenEnglish]

vksy.. just saw that you confused the lm317 pinout: the way you mounted the regulator to the heatsink you'd have the input pin on the right, output in the middle, adjustment-pin on the left side! in your schematic the output is on the right, adjustment in the middle, input left... it will not work this way...

 

[vksy]

Quote:

vksy.. just saw that you confused the lm317 pinout: the way you mounted the regulator to the heatsink you'd have the input pin on the right, output in the middle, adjustment-pin on the left side! in your schematic the output is on the right, adjustment in the middle, input left... it will not work this way...

Thanks for taking the time to go over the psu layout. I appreciate your help. It is now updated with the correct regulator orientaion. I don't know how I missed it since I only looked this over a hundred times!!

Just to be on the safe side, I also added a word of caution in previous posts (something I should have done earlier).

 

[BrokenEnglish]

Quote:

Originally Posted by vksy It is now updated with the correct regulator orientaion.

no... you still have to route the output from the middle pin of lm317!
hey... and don't mind, vksy... this sort of mental rotation stresses my brain each time i try to handle those three-leggers...

 

[vksy]

Quote:

no... you still have to route the output from the middle pin of lm317!

Pin 1 - Check!
Pin 2 - Check!
Pin 3 - Check!

Quote:

hey... and don't mind, vksy... this sort of mental rotation stresses my brain each time i try to handle those three-leggers...

I need to take that eye exam I keep postponing. It really helps to have a good prescription when working with this stuff.

 

[BrokenEnglish]

yeah.. you're done! thanks, vksy!

personally i'd bring r3 nearer to the pins, as recommended in the datasheet. just a suggestion...

 

[vksy]

Quote:

personally i'd bring r3 nearer to the pins, as recommended in the datasheet. just a suggestion...

Besides R3, are there any other improvements I should consider? My goal is to have a workable layout for bare P2P, but I don't mind rearranging components as long as it doesn't result in signals crossing paths.