Tuesday, 10 December 2013

Best Case for the Job

Prototype Follow Up

I love the range of cases from Hammond Manufacturing. The only draw back with these cases is that in one off quantities, they are expensive.

What I love about the Hammond cases is that Hammond supply excellent 3D cad models of all their products, a you can use these to help created great looking project mock ups before you spend a cent.

Hammond 1593NBK Step Model in Altium

With Modeled Prototype Alarm Interface Circuit

And the Real Deal

I liked this case, and it's not too expensive.  My only drawback was the board shape - the indents to clear the mounting posts has an effect on the routing, and this made the routing of my board a tad messy.  Time for a new case.

If You Build It

From my series on my alarm interface, you can see that I learnt a few things on the way, some times through planned experiments, some times through trial and error.  To finish this project, and to correct some shortcomings of the prototype's PCB layout, I decided to bite the bullet and take a second cut.

Hammond 1455J1201BK

Because I had access to a few of the Hammond 1455J1201BK cases lying around, I laid out my alarm interface for a second time, fixing my past errors and adding minor improvements.  Then I took a look at the cost of the case.  $25 each.  YIKES!

Although the cases look great, no way was I going to use a $25 case. So I started to look around for alternatives.

Long story short, Seeed Studio supplies these cases, for a sweet $7.50.  The PCB dimension of 68 x 110 mm is pretty close to the Hammond 75 *123 so I decided to go with the Seeed case.  In fact, my buddy Marc added two cases to his last Seeed order for me, thanks Marc!

Seeed Case, Picture Shamelessly Ripped from Seeed's Site 

The only drawback, was there wasn't any CAD information to hand, and there wasn't a step model to be imported.  Dammit, I was going to have to fix this myself....  And if I was going to fix it, I was going to share!

PCB Sizing

First step was to size the PCB.  Seeed quote the case as being 113 x 70 x 25 mm, and this is the EXTERNAL dimensions. The internal profile is slightly less (the end plates have thickness) at 68 x 110 mm.  

But beware, you cannot use all that board space.  The PCB slides into guide rails in the case, and these must be clear of any components.  Your working area on the PCB is limited to 63 x 100 mm.

As I work in Altium, I've made both Alitum and DWG files available of my PCB template (Altium exports to DWG, and I just use the defaults, with the exception that I have chosen 'Metric' rather than 'Imperial' units).

Export Options

PCB Profile

Feel free to use / share as you wish!

End Profile

The great thing with all extruded aluminium cases is the it's easy to design end plates for them, once you know your profile.  I measured up and laid out profile boards to share, again in Altium and DWG formats.

PCB End Profile

3D View.  Look!  Mounting Holes!


Okay, you got me. Beyond simple shapes, Altium sucks at producing 3D models.  However, one of the friendly CAD guys at work is learning how to build 3D models and was happy to take my profile and turn it into an extrusion, and also spun out some end plates.  Woohoo.

Here are the case and end plate step models, and the Altium PCB file with the above PCB template and the case / ends embedded.

Newly Created Seeed Case in Altium, With End Plates

All Together

With the new step models of the case available, it was then a (long) lunch to lay out my alarm interface (for the third time) into a snazzy looking unit!

V1 Alarm Interface


I've greatly benefited form the open community out there, and it feels good to be able to give back.  So for your next project, grab a $7.50 case from Seeed and 3D model to your hearts content.

1 comment:

  1. The article is much informative which i was searching for .Nice intro good explanation thanks for sharing.