Hypomnemata

We’ve found a bug in the Volksduino v1.2 PCB, related to the power jack. There is no danger to power supplies or the Volksduino if you plug in a power adaptor: the problem is actually that the jack isn’t actually connected to the circuit correctly. This is a problem with the 1.2 Volksduinos, which are nearly sold out, so we don’t anticipate many problems with this. This post is mostly for anyone who happens to want to add power to an older Volksduino at some point in the future.

First off: sorry! We screwed up. The original Volksduino (v1.0) had a few problems, which were fixed in v1.2. Somehow, this one slipped through the cracks. We’re especially sorry that it took so long to find this out and document it. Since we don’t usually include the barrel jack (in our experience, no one uses it, and it’s one of the hardest parts to solder for new solderers), it took nearly the full first production run of the v1.2 for someone to notice it. In any case, this is entirely our fault, and we’re working with folks who are affected to try and make things right. There isn’t a Volksduino 1.3 in the plans at the moment, unfortunately (we’re focusing on other products, which are a bit more “different” than Yet Another Arduino Clone).

Anyway, let’s get down to fixing this thing. The problem is with the pinout of the barrel connector. Instead of connecting the power input to the ring and center pin (ie: ground and positive voltage), it’s connected to ground and the “power supply is plugged in” switch. There is no danger to your power supply or stock Volksduino: it’s just that the wallwart’s positive supply isn’t really connected to anything.

The problem is that the wrong pinout was used for the power jack, so we need to cut one trace (“wire” on the PCB) and run a quick jumper from the jack. Here are images of the two step:

1. Cut the trace, (and where to do it, and what a cut trace looks like):

2. Run a jumper wire between these two points:

Fuller details:

Tools needed to fix this:

• Multimeter for continuity testing
• X-acto or similar sharp, maneuverable knife
• soldering iron
• solder wick (radio shack has it)
• short length of wire, preferably 22 or 20gage stranded

Problem description: the power jack pinout is wrong. We need to cut the socket-D1 trace and add a jumper from VIN+ to the barrel jack terminal closest to the 7805.

A quick, overly thorough textual walk-through:

1. Test for continuity between the left/outside VIN pin and the bottom pin of the power socket (on the top of the board, it has “7~15VDC” printed through it). On a stock board, this will be a short.
2. On the top of the board, there’s a trace running between the socket and D1′s anode (right under the letter “1″ in “1N4004″). Between the socket and the diode (ie: right next to the socket), cut this trace with the x-acto knife. This is a very thin layer of soft copper under a thin layer of soldermask, so you don’t need to press hard. It’s sometimes helpful to make two angled cuts, cutting a “v” in there.
3. Once this is cut, test continuity again. If it’s still connected, try making your cuts a little deeper. Keep going until these aren’t connected.
4. Flip the board over, and use solder wick to remove a lot of solder from the socket pin closest to the 7805 (it’s on the left when the board is flipped over). We want to get to the little hole in the terminal, so it shouldn’t require pulling off too much solder.
5. If the little hole doesn’t want to clear out, heat up the solder, and gently tap the edge of the board on the table. It’ll probably come loose.
6. Make a short jumper of wire, just long enough to go into the outside hole of VIN and run through this hole.
7. Solder that wire in.
8. Plugging in the wall wart should now light the power LED.

Make sure to keep the wire short, and that the insulation covers things well, which makes this a reliable repair.

If you run into any questions or problems, email support@appliedplatonics.com and we’ll get everything sorted out. Apologies again for the bug!