PCB0003 - Breadboard supply

This is a very simple PCB based on the LM317 voltage regulator. For years I used a 7805 on the stripboard below, a fixed 5v output and really poor layout on my behalf.

The PCB sits across the end of a normal breadboard and powers both rails. The input is protected with a resettable PTC fuse and the output is selectable between 3.3v and 5v using a jumper.

Spacing of the 2 pin headers for the breadboard rails was achieved using the highly technical method of "try it and see". It transpires that the theoretical measurements are quite precise. Printing a circuit onto paper like this is an excellent way of making sure your parts fit before sending it off for manufacture.

Revision2 boards have a diode in series with the input (to protect against reverse connection of the power supply), better spacing for the optional output headers and holes for an alternate input (e.g. a 9V battery).


Download board (ZIP) - Eagle files
Schematic (PDF)


This work is made available under the Creative Commons Attribution-NonCommercial-ShareAlike (CC BY-NC-SA) liencse.

Attribution-NonCommercial-ShareAlike CC BY-NC-SA

9 comments on “PCB0003 - Breadboard supply
  1. RB says:

    Hi David. As you know, I have built this neat little circuit with your PCB and can attest it works very nicely! My only (cosmetic) suggestion for a 3rd revision would be to rotate the LM317 180 degrees on the PCB layout - as I added a small clip-on heat sink to the IC, but the large capacitor fouled it, so had to bend the LM317 out and away from the PCB edge to get it to fit.

  2. David says:

    Send over a photo of the completed board, my intention was always that heatsinks would sit off the edge of the PCB. Unsure what type you used, I thought the only obstruction would be the input socket.

  3. Gerben says:

    Thanks for sharing the eagle files. I'm currently modifying it to work with a 7805. I did however notice your breadboard is 0.2inch wider than mine (-:

    I'm still quite new to Eagle, so your schematic and layout were a great starting point. So thanks again.

  4. David says:

    I'm glad this was useful. It seems to work fine on all the breadboards I have, what kind is yours? It would be great to see a picture so I can work out whether it would be possible to modify my board in future.

  5. Gerben says:

    Here is in image of 3 of my breadboard with a printout of your schematic on top http://i.imgur.com/XtzvMef.jpg?1 . All bought from different stores. The board is 0.2inch too wide. Distance between the outermost sockets on the breadboards is 1.9inch. Pretty weird.

    My altered board has just been etched, and came out excellent. Not the prettiest layout, but with limited space and some esthetic constraints, I'm pretty pleased. Tomorrow I can drill the holes and start populating it.

  6. Viral says:

    I want to use this circuit for my +24V input voltage to +5v output to microcontroller TTL logic which modification needs.

  7. David says:

    This circuit isn't really suitable for the large voltage drop from 24V to 5V because it is a linear regulator. You would need a very large heatsink. For your input voltage it would be much better to use a switching regulator.

  8. Viral says:

    It can be use to convert +12v to +5v supply????

  9. David says:

    +12v is still a very high input for a 7805, even at low currents. See this question and this question at Stack Exchange. At minimum you will want a large heatsink if you choose to use a +12v input voltage with this board.

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