Several months back I posted an adjustable output voltage regulator board based on the LM317T IC, here. A few days ago I was contacted offline by a gentleman who wanted the same board, but narrow; only 1/2" wide. I made a version for him and ordered a dozen of them shipped to him direct. I thought I might as well post the build files here in case others may have need for an extra narrow regulator board. Costs are about $5.00 each for all domestic boards and parts; or about $1.00 each for offshore components.

Here is the circuit and a 3D depiction of the completed board. It uses all the same components as the previously posted board, above. The circuit is identical.

Circuit Snip

Top Front 3D View

The User Notes in pdf form and Gerber zip file are attached below. The BOM is identical to the earlier board.

Have fun, Rod

 

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Last edited by Rod Stewart
Original Post

Rod, looks good.  How long is the board in this configuration?  BTW  Thx for all your time and trouble on these pcb applications.  😉

TedW posted:

Rod, looks good.  How long is the board in this configuration?  BTW  Thx for all your time and trouble on these pcb applications.  😉

Hi Ted. The board is 45 mm long, about 1-3/4". Sorry I did not include that in the description. To be clear, its exactly the same board as the earlier post circuit-wise, just narrower, which may help in some folk's applications. 

Rod

Rod, after linking back to earlier LM317 threads there is the dangling participle of isolated AC vs. DC ground.  Does the 3-D rendering function allow you to "install" a 2-cent 1N400x diode into 2 of the 4 bridge pads (AC to +) and, say, a jumper wire between the other 2 bridge pads (other AC to -)?  This would allow the same board to be used for 1/2 wave rectification where the AC and DC grounds would be the same which can be handy in some rolling stock applications.  This can also be handy in track-side applications making it directly compatible with insulated-rail triggering.

Separately, I may have missed it but I didn't see discussion of using the LM317P insulated package which would allow you to bolt the LM317 directly to the chassis/frame from heat management. 

IMG_5820

That is, finding those insulating washers and related hardware pieces can be a nuisance.  The insulated package is harder to find but can be expedient albeit at a price.  You can't get a whopping deal on eBay as you can with the LM317T (metal tab) for less than a dime.  While there are several eBay sellers of the insulated package, this may be the rare case where buying from DigiKey is cheaper! 

 

 

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Last edited by stan2004

FWIW, no extra components required, just a set of jumpers.  I just use one of the diodes in the bridge for the half-wave option.  Here's how I did a switchable board, in this case this is mated with an eBay switcher to provide power at greater efficiency than linear regulators.

__000000

This is the board and the regulator board sandwiched below it.

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stan2004 posted:
That is, finding those insulating washers and related hardware pieces can be a nuisance.  The insulated package is harder to find but can be expedient albeit at a price.  You can't get a whopping deal on eBay as you can with the LM317T (metal tab) for less than a dime.  While there are several eBay sellers of the insulated package, this may be the rare case where buying from DigiKey is cheaper! 

That's true Stan, Digikey and Mouser have them for less than a dollar in quantity one, I didn't find one cheaper on eBay or places like Aliexpress.com

gunrunnerjohn posted:

FWIW, no extra components required, just a set of jumpers.  

IIRC, we had this discussion a few years back.  I believe if all 4 terminals of the bridge are soldered-in, you have to cut trace(s) on the board?  OTOH, if you know ahead of time that you want half-wave rectification for common-ground operation I think you can "simply" bend up one or more terminals of the bridge and solder less than 4 terminals.  Then add a jumper or whatever.  The point being cutting a trace with an x-acto knife or whatever is a bother.

In any case, the idea is to document these options, alternatives, etc. in the same spirit that the guys are consolidating the various PCB projects.

I was curious if these 3-D renderings allow you to "install" a 2-terminal diode into 2 of the 4 terminals of the bridge and show what it would look like.  Or, for example, to cut off or "bend up" one or more terminals of the bridge rectifier and show what it would look like installed. 

 

Stan, I added the jumper field to solve any cutting issue.  That allows me to build the board with both capabilities and just jumper it for the desired operation.

There's a little fooling around to try to graft components in that aren't in the design.  I suppose it could be done, but I'm not sure how much effort it would be.  I think the way to do the resistor substitution would likely be just change the 3D file to a resistor and then try to position it.

Just as a FYI, the version Rod posted here has been added to the main Projects list in the Electrical Reference thread. (Link below in signature line)

Stan; thanks for these two very good ideas. You are the master of timely helpful suggestions! 

I actually have in my user notes that the grounds must be kept isolated, and that if the supply is DC you can just jumper the bridge rectifier pads. But I never considered the idea of adding a simple diode to the + side and jumpering the ground side to achieve common-grounded half wave rectification. Think I'll go back and add that to the user notes.

The insulated 317P is also a nice option. I checked Digikey and they can be had for less than $1, compared to anywhere from $3 to $5 each, and more, on ebay. So definitely DK is the way to go. I'll also add that to the user notes.

Thanks again for your valuable input! 

Rod

Whoa, I see that by the time I got around to responding to Stan's suggestions, there had been all kinds of posts added. Lots of good comments here. 

Rod

Of course a lot of this is just for sport.  That you got the cost down to a 85 cents all-in is amazing enough!  

So, for those applications that need common AC-DC ground, why not save a nickel using a 1-cent diode instead of a wallet-busting 6-cent bridge!

diode vs bridge

 

 

 

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OK I removed the original user notes from my opening post and added a new set R2.2a instead, that incorporates both Stan's suggestions. Tom, you may need to re-link the user notes because of the different name; not sure?

Rod

stan2004 posted:
gunrunnerjohn posted:

FWIW, no extra components required, just a set of jumpers.  

IIRC, we had this discussion a few years back.  I believe if all 4 terminals of the bridge are soldered-in, you have to cut trace(s) on the board?  OTOH, if you know ahead of time that you want half-wave rectification for common-ground operation I think you can "simply" bend up one or more terminals of the bridge and solder less than 4 terminals.  Then add a jumper or whatever.  The point being cutting a trace with an x-acto knife or whatever is a bother.

In any case, the idea is to document these options, alternatives, etc. in the same spirit that the guys are consolidating the various PCB projects.

I was curious if these 3-D renderings allow you to "install" a 2-terminal diode into 2 of the 4 terminals of the bridge and show what it would look like.  Or, for example, to cut off or "bend up" one or more terminals of the bridge rectifier and show what it would look like installed. 

 

I think if you know ahead of time that you need a common ground, the easiest thing to do is leave the bridge out, put a diode across from the near ac connection to the #1 pad (+), and a jumper from the other ac connection to board ground. Presto, done. No trace cutting, no bending, no muss, no fuss! 

Rod

All is well, the Projects post links to this entire thread. All the projects are linked to their original threads for getting further info and/or files.

I realize the train has left the station, but two other comments for the record.

lm317 pcb ideas

1) Will a 3296W trimpot physically fit in the space allotted for the 3362P - without bumping into the cap or bridge?  It's a little longer/wider and it would require a new pad to be dropped on the board since the terminals are in-line albeit on a 2.54mm grid.  The idea is to allow either style of trimpot to be inserted.  The 3296W is multi-turn as used in the ubiquitous LM2596 stepdown regulator modules that we have come to know and love.  Same cost on eBay when I just looked. This might be a nice project for someone getting started with DipTrace and could take Rod's existing design and make a minor modification with a high likelihood of success while contributing to the cause (in my opinion of course).

2) For some applications with low-current, it might make sense to install the TO-92 version of the LM317.  Might be even cheaper depending on where you buy.  The idea here is very few designs come anywhere near requiring the >1 Amp capability of the LM317T.  In fact I seem to recall real-user data where the current required in a passenger car LED application was 5 mA (or less)!  In such a case there's no need for the TO-220 version which of course is a rather large package.  Commensurately, you would not need a 1000uF capacitor to achieve a suitable flicker reduction...and could use, say, 220uF or less which would allow even a smaller overall space requirement.  Again, the idea here is to create what amounts to an Application Note for Rod's board design.  I suppose if someone learning DipTrace wanted a simple modification project to get one's feet wet, they could add 3 pads on a closer grid to install either the TO-92 package or the TO-220 package (same PCB board)...and contribute to the cause (in my opinion of course).

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Last edited by stan2004

You could also add a pad for a diode under the bridge so that you didn't have to guess where the diode goes. 

FWIW, the board could also be smaller, no reason to have all that space between the choke and the pads.

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stan2004 posted:

2) For some applications with low-current, it might make sense to install the TO-92 version of the LM317.  Might be even cheaper depending on where you buy.  The idea here is very few designs come anywhere near requiring the >1 Amp capability of the LM317T.

I did a fixed voltage version using the TO-92 chip. 

It's less than an inch long and .3" wide.  You can use any voltage three-terminal regulator in the board to pick a voltage.  You can also stick the CL-2 constant current regulator in the board with no changes for a constant current application like LED lighting.

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Bob, the heat sink is up to the end user, and will vary by application.

John, the space between L1 and the pads is to permit the use of connectors like the small green 2.5mm screw terminals. For the final run I did in fact shorten the board a little, it is about 1-3/4" long.

I do like the idea of the additional diode pad under the D1 pattern; will likely add that to the design. 

We need to remember that one of the objectives here was to stick with easy thru-hole design so that most folks (like me) can build it without too many issues.

Rod

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