Archive for Organisation

An Extra Special Parcel from China

This is a slightly different post than usual. Typically, I try to only post progress that has already been done, otherwise it ends up as so much vaporware.

For an upcoming project, I wanted to order some parts, write some code, and then use the code to order more parts, but it’s taking a backseat at the moment. So I’ll write about the intended roadmap, instead.

 

For some backstory:

AliExpress is great. There is a ton of cheap stuff, but it is a littttle bit limited in stock. Popular items only.

Taobao is the answer to that. Chinese language only, but it has everything. Google Translate is your friend. They also don’t ship internationally, but there are reshippers that get around.

Reshippers/fulfillment services are starting to pop up everywhere. I have gone through DirtyPCBs’ service, and the price breakdown is like this:

$item cost + $magic shipping cost + $3 per vendor
+ $15 shipping fee + 15% declared value customs fee

 

That eats into the savings pretty quickly if you’re buying $2 semiconductors from 5 different vendors. That $2 vendor fee is the largest cost that is avoidable.

 

The obvious optimisation here is to find all items as you’re trying to purchase, from as few vendors as possible. Many will have a large amount of semiconductors, for example, but no easy way to sift through the matrix of what they’re selling and how it matches up to your shopping cart. That is the basis of what I’d like to do. I’ve written a rudimentary scraper that can grab search results and merchant data, but no overall design of how the interface should look, or how data should be displayed.

 

A good proof-of-concept to try and spur me on to start implementing this came up recently, when I got a generous offer of PCB coupon from Seeed Fusion. I’ve used them before (and bought items from the marketplace, too!), and they’re an awesome company, so it was very appreciated.

I opted to get a few copies of Benjamin Vedder’s vESC project.

It’s a nice candidate for this because each board requires six expensive MOSFETs(IRFS7530) that cost about $7 each. Taobao lists them at closer to $0.80, although the quality is somewhat suspect.

These boards look fantastic, however:

 

I opted for yellow, expecting a loud, obnoxious colour, but this turned out to be a very pleasing orangish hue. I may use more of this soldermask colour in the future. Because it’s a 4-layer board, you can see internal layers in the fibreglass that change the look significantly, so I can add three totally different FR4 shades in the “Seeed Fusion yellow” entry in the colour palette I’ve been maintaining.

 

So this is currently in a mostly-shelved state. When I have a more pressing need for it, I will continue with the Taobao companion application (codename: TaoBeau), and attempt to build out the Seeed board with a $20 BoM cost instead of the Digikey cost of around $90.

Laser Cut Spice Racks

I’m still transferring my SolidWorks knowledge into Fusion 360, and definitely getting the hang of it.

 

Previously, I was having troubles mating parts properly, which totally makes sense. The way Fusion 360 and SolidWorks handle these concepts are the largest difference in workflow so far.

 

Where SolidWorks requires each “part” to be one object, and all parts must be added to an “assembly” for positioning and mating, Fusion 360 allows all of these to happen in one file. When a part is created, however it is called a “body” and must be turned into a “component” before repositioning or aligning it with other component. I’m not sure the benefit of this, but hey, that’s how it works. After a body has been turned into components, the “joint” command is analogous to SolidWork’s “mates”. They’re a little bit more finicky, but they work.

 

shelf v25

 

Here’s the latest experiment. Once again, this is almost entirely parametric. I had an idea to store all of my surface mount components in vials, and this is a pretty ideal way to stack them up. I realised about halfway through that, while designing a vial storage rack, it’s basically a spice rack.

One of the problems with this, is that over time I’ll be adding to it. Next time I need to laser cut some more, am I going to be able to find the same size of container? Am I going to be able to use the same size of material? What if I want a different sized rack to fit into a particular spot? Parametric!

There are a lot of variables in this one. Fortunately, most don’t have to be touched, usually.

In adapting these for different container size, the important variables are shelf_numVials and all of the vial_ parameters.

 

For the larger ones I got from the dollar store, they are:

vial_height = 48.75 – 11.5mm

vial_diameter = 27.5mm

vial_lidheight = 11.5mm

vial_lidDiameter = 31.25mm

These are unlikely to be available anywhere else.

 

 

The smaller ones from China are:

vial_height = 49 – 9mm

vial_diameter = 10.75mm

vial_lidheight = 9mm

vial_lidDiameter = 12.5mm

These are orange-lidded, 1.5mL plastic test tubes from AliExpress.

 

 

I’m now at revision 3 – The first one I cut sagged a little more than I would have liked, so I designed in a back piece at a right angle to straighten everything up.

Spice Rack R1

 

That worked, and stacking R2 on top of the first version pushes the ends out – effectively pulling it straight.

 

All of my files are available on GitHub here, or through Autodesk’s weird cloud platform.

Here’s an older version showing them stack:

http://a360.co/1X4LDGb

 

Here’s the latest version with all the bells and whistles:

http://a360.co/21Q52Bq

This is the one you want, if you’re planning on doing something similar.