The Bikeshed Board

[mike]

Hey all,

One of my other projects ( BLE MIDI kit dev blog) needs the ability to be powered from USB at 3.3v, as well as charge and discharge a battery, and ideally, not reset when you plug in/unplug the usb.

As I’ve learned recently, this is called power path management. The question about how to do this has come up a few times on the VHS slack. I’ve gone ahead and designed a board that will hopefully satisfy this need and once I figure out any bugs, I’ll incorporate it into my other project.

Throughout the last few days, I’ve been asking a lot of questions on the slack circuit board design channel, and I got some great feedback! One of the silly things that has happened though is I’ve gotten requests (or rather, suggestions) for a change of the USB port, twice. In proper :allthethings: fashion, I’ve instead just added ALL of them to the board.

I present to you, the most ridiculous power path board ever made.

It has MicroUSB, MiniUSB, and USB-C connectors (you really should only solder one, but I won’t stop you if you want to solder more than one). It supports Lithium-Ion charging, and outputs sweet sweet 3.3v… in theory.

I sent it off for fab tonight. If this all goes well, I’ll make this board available as a kit.

[mike]

Oh, and because OSHPark PCBs are extra snazzy, here’s their preview image.

[mike]

Based on some bikeshedding, it seems like this board really ought to be shaped like a bike shed.

Other than the color, I’d love some creative feedback on my proposed board shape.

Thanks!

[mike]

I had to keep going. Getting those paths in was more work than it should have been. !

This is a very rough layout, most things are in there (only 1 USB connector, trying to figure out how to be super-clever about placement of them all…

I’m digging the status indicators as spokes…

[Jarrett]

What’s the size of the USB-C connector like? Can you fit another USB port in the same footprint in a mutually compatible way?

[mike]

With a little offsetting I think I can, but the electrical connections get in the way for too much of an overlap.

[mike]

@Jarrett, turns out the micro fits in the C

Think the case from the USB-C would short the traces for the micro?

[Jarrett]

For sure. Bottom of board?

Also those red crosshatches are probably cutouts, for non-conductive mounting pegs, looks like they might take out the traces in the position

[mike]

I believe those are actually the clearance for the hole, since it doesn’t actually pierce the board.

[mike]

I gotta hand it to OSHPark.com, I ordered it on the weekend and it is already panelized and sent to fabrication!

[Janet]

I love Oshpark. Such a great company. I’ve only done 2 boards with them but all have been really good quality. Also purple boards are teh best.

[mike]

Coming along… I have mounting holes all over, PTC fuse, status indicator pinouts, a bit more spacing for the resistors so they are easier to place (still going to be a pain). MicroUSB is in there on the reversed side.

The last major thing to do that is on my list is to add a couple ESD diodes for the CC lines, and of course test the first prototype to make sure most of the first assumptions are correct.

Also, I realized that I don’t need an SAO connector since my original output already complies to the power spec!

[mike]

Okay;

I’ve got 2 sets of boards coming in. I’m not an SMD soldering master (I’ve SMD soldered fewer chips than I have fingers).

I’ve got all the parts and boards on their way. While I’ll be soldering up a few myself, if anyone is interested in helping me validate this board, I’ll provide you a free board and set of components if you want to be beta tester!

Please sign up here if you are interested. I’m arbitrarily setting the limit it at 5 slots. Board and components should be here in ~3 weeks.

[Gavitron]

I’m interested in helping.

[Arrgh]

I’m in!

[Janet]

Woot! I am in!

[mike]

Awesome, thanks everyone. I’ll keep you updated with the shipping process.

How should I go about making a stencil? OSHPark didn’t seem to have that as an option. I assume I can output a layer and just etch that on something on the laser?

[Jarrett]

I probably wouldn’t worry about a stencil on a small one-off like this, just steady hands and a syringe.

For the future, OSHStencils is a thing that people like, alongside OSHPark.

Or, you can also pick up mylar sheets (projector transparencies) and laser etch those.

[Janet]

I’m totally hand-soldering this!

[mike]

@Jarrett

OSHStencils is a thing that people like, alongside OSHPark

OMG! how do they hide this so much, or is it a different group (page looks different)?

Just a warning, many of those are 0402… that’s still hand-placed range, right?