Steve's Build Log


I really like it. At least having done the Power Swap module of CE I at least understand the principle of the suggested design. The down side with a vendor specific tool is that I might be missing out on more suitable parts from other suppliers.


I was inspired by the recent videos from @ChrisGammell to have a go at custom/complex board shapes. I had experimented with this before but never brought the shape to OSH Park. Also taking the lead from the Tindie badge, I came up with a simple design that uses some RGB Rainbow LEDs. My first encounter with these devices was at a Makerfaire where someone was immersing these in a mould filled with hot-glue to make small blinking animals - very cute.

My shape is simple (corny) enough. My thought is as a soldering experiment to encourage a junior maker. I created this in Inkscape simply using a series of circles for the head, ears, body, legs and paws. I saved/duplicated the shape at various stages so that I could either reuse or go back if things did not work right. This proved helpful as once I started to import things in to KiCad, I realised I needed different shapes for different aspects of the board, namely the following shapes:

I pretty much followed Chris’ example and it all worked without issue. I also included the steps for inverting the images in GIMP before importing to KiCad. The theory behind this is that when exporting from applications like Inkscape, the white background on the screen will be converted to the Alpha (transparent) channel in the exported image. This causes big problems with the bitmap2component import. There can be no alpha channel. The work around is to invert the image in applications like GIMP or place a white enclosing box behind the image.

Since playing around with this, I have now realised the setting in Inkscape to ensure a white background and no Alpha channel. It can be found in the “Document Properties”, “Background color”, setting everything to white with 100% opacity. Using this saves the extra work step of inverting the image in GIMP.


Excellent work! Thanks for sharing the Inkscape settings. The gold enig on the Oshpark boards really looks fantastic with the bear heart.


Thanks Jon, I am very happy with it as a case study in custom board design. It even does not look too bad when in operation.


Yeah, this is a super cute design! I feel like I have to get deeper into inkscape. I’m a bit dependent upon Sketch (by Bohemian Coding) for a simple/intuitive way to manipulate SVGs, but that is mac only. I highly recommend people start with SVGs for PCBs, I think there’s a lot of value in planning out the art that way (this is also what Saar from Boldport does for his boards, albeit in a more in-depth manner)


I certainly agree and the operative word is planning. I did not do it for the bear but I could have mixed and matched the fill zones like you did for your project. This way, I could have avoided a couple of tracks.
Now, as of writing, I was curious to check in KiCad and it is possible to export the layout as SVG. This means that a complex fill zone shape could be created in Inkscape or Sketch after parts placement.


Leading on from what I learned from the Blinky-Bear project, I wanted to try something a little more practical. I thought about a AA Cell replacement board for a small trimmer where a normal alkaline battery has trouble powering it for any length of time - From the Lab Power supply the device draws around 700mA.

I figured a 5V to 1.5V LDO should do. The circuit is simple enough - based on a ADP3339AKCZ-1.5-R7. Not exactly the cheapest option but it is available and should be able to handle the power requirements. The idea is to use a USB Micro B connector. For this, I will have to modify the case to enable the USB cable to be plugged in.

For the layout, this time I started in Inkscape, rather than KiCad Pcbnew. I made a few attempts before I finalised on a design that will comprise of two boards that will slot into each other to make up the bulk of the AA-Cell shape. I figured I could save a couple of dollars in the by laying out the boards end to end rather than side-by-side. I just had to make special consideration for the “panelisation” of the two boards. For this I consulted the OSH Park design guide document “Panels and Designs”. I actually submitted the boards without an order and requested OSH Park Support to take a look. They were more than helpful and pointed out that I needed to remove the edge cut going through the mouse-bites.

The fix for this was to ensure that the edge cut does not go through where the mouse-bit is expected to be positioned.


I have only just submitted the boards to OSH Park, so I am curious if this will all fit together as I am anticipating. There is certainly a bit more work when doing the edge-cut this way but in the end, I am finding I am spending more time on mechanical aspects of a project than the actual electronics.

This brings me to another point I missed describing on a previous post. Namely another Inkscape setting. In Edit, Preferences, the main preference page gives two options - Visual-Bounding-Box or Geometric-Bounding-Box. The difference in the two options is illustrated below - essentially, visual puts the bounding box on the outside of the line. Whereas geometric places the bounding box in the centre of the line. I personally find the Geometric bounding box easier to conceptualise with respect to the edge cuts.


Is this because it matches the toolpath of a milling bit?


That is certainly the case for a laser cutter - for the milling bit, I am not 100% sure. the graphic on the OSH Park Board Outline document implies that this will line is the outside edge of the tool cut. I am making this assumption and when I get the boards I will then know for sure - it’s a prototype :slight_smile:


I am still waiting for the Tag-Connect Edge Connector to come available in Europe - Here is the comparison of my current footprint to the sample. This is also my first attempt at castellated edges with KiCad. Sort of not bad but I will wait to try with the real connector before submitting again.