Standoff size and side height

Standard PCB templates and project cases

Re: Standoff size and side height

Postby dsm » Fri Mar 30, 2012 7:30 pm

Scheme G v4 update - part II

I uploaded the Scheme G v4 top and bottom magnet holder parts to Shapeways.
There are several variants available to support various acrylic thicknesses.
In order to reduce the effect of the Shapeways flat handling fee, there are groupings of
4x pairs (one case) and 16x pairs (four cases) available.
  • 1.5 mm ~ 4x pairs (link)
  • 1.5 mm ~ 16x pairs (link)
  • 2.55 mm ~ 4x pairs (link)
  • 2.55 mm ~ 16x pairs (link)
  • 3.0 mm ~ 4x pairs (link)
  • 3.0 mm ~ 16x pairs (link)
SoB-case-SchemeG-4x-pairs-barb-50x18x15-assembly-for-SLS-dsm-v4-orthographic.jpg
SoB-case-SchemeG-barb-50x18x15-dsm-v4
1.5 mm acrylic ~ 4x pairs ~ orthographic

SoB-case-SchemeG-16x-pairs-barb-50x18x15-assembly-for-SLS-dsm-v4-orthographic.jpg
SoB-case-SchemeG-barb-50x18x15-dsm-v4
1.5 mm acrylic ~ 16x pairs ~ orthographic

SoB-case-SchemeG-4x-pairs-barb-50x18x255-assembly-for-SLS-dsm-v4-orthographic.jpg
SoB-case-SchemeG-barb-50x18x255-dsm-v4
2.55 mm acrylic ~ 4x pairs ~ orthographic

SoB-case-SchemeG-16x-pairs-barb-50x18x255-assembly-for-SLS-dsm-v4-orthographic.jpg
SoB-case-SchemeG-barb-50x18x255-dsm-v4
2.55 mm acrylic ~ 16x pairs ~ orthographic

SoB-case-SchemeG-4x-pairs-barb-50x18x30-assembly-for-SLS-dsm-v4-orthographic.jpg
SoB-case-SchemeG-barb-50x18x30-dsm-v4
3.0 mm acrylic ~ 4x pairs ~ orthographic

SoB-case-SchemeG-16x-pairs-barb-50x18x30-assembly-for-SLS-dsm-v4-orthographic.jpg
SoB-case-SchemeG-barb-50x18x30-dsm-v4
3.0 mm acrylic ~ 16x pairs ~ orthographic

Thanks for your time.

dsm
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Re: Standoff size and side height

Postby ian » Sun Apr 01, 2012 4:28 am

Thanks for adding them to shapeways dsm. I ordered the 2.55mm 16 pairs variant from Shapeways, with shipment expected by the 11th. I used strong, flexible, and red material, I believe the same you have been using.

We will also make matching acrylic panels at Seeed and have them held in store so we can pick them up directly next Saturday. I will also discuss the laser tolerances on our Seeed tour.

Attached are some pictures of the Bus Pirate versions and accessories in the updated form factor. The v3.5e is in the v2 Scheme G case.
Attachments
IMG_20120401_111901-W600.jpg
IMG_20120401_111854-W600.jpg
IMG_20120401_111907-W600.jpg
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Re: Standoff size and side height

Postby dsm » Sun Apr 01, 2012 4:45 pm

comments

ian,

The Scheme G v4 parts on Shapeways could probably built in groupings of 64x pairs before you run into the upload file size limits of the Shapeways web site. I would be happy to implement and upload these larger groupings if you think Seeed Studio might find this to be useful. Changing to a lower resolution STL "mesh" size might allow the number of pairs to be increased somewhat, but for various reasons I suspect this is a poor tradeoff. In the interests of full disclosure, I've been adding a $1.00 markup to each my designs on Shapeways - mostly as a means of tracking which of my designs have been selling. Amortized over 64x pairs, this markup would be roughly $0.015 per pair (or roughly $0.06 per case).

The advantages of 3D printing Scheme G parts include
  • Easy to print parts that accommodate thicker and thinner acrylic windows.
  • Easy to print parts that allow different above-the-board and below-the-board spacings.
  • Easy to print parts in other materials.
  • Easy to print parts in standard Shapeways colors (which are currently being expanded).
  • Easy to print parts in white nylon (and dye them to whatever color you want).
  • Easy to order parts over the internet and pay for them with PayPal.
In the long run, I assume that Seeed Studio may want to arrange for their own injection molded Scheme G parts.
You might want to make sure that Seeed Studio understands the differences between
  • the nominal dimensions of injected molded Scheme G parts.
  • the actual dimensions of 3D printed Scheme G parts via companies like Shapeways.
You might want to make sure that Seeed Studio makes a reasonable choice for orienting the neodymium magnets.
I've been installing the neodymium magnets so that
  • the "north" pole [1] is sticking out of the bottom Scheme G magnet holders.
  • the "south" pole [2] is sticking out of the top Scheme G magnet holders.
Thanks for your time.

dsm

[1] "north" pole refers to the end of the magnet that is attracted to the earth's north magnetic pole.
[2] "south" pole refers to the end of the magnet that is attracted to the earth's south magnetic pole.
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Re: Standoff size and side height

Postby dsm » Sun Apr 01, 2012 5:19 pm

more comments

ian,

Regarding the 1.5 mm vs 2.55 mm vs 3.0 mm acrylic thickness issue...
    I personally like 1.5 mm thick acrylic because (a) it is widely available, (b) low-cost, (c) allows thinner cases, (d) strong enough for most applications, (e) low weight compared to the strength of the neodymium magnets, and (f) slightly flexible. On the other hand, (a) the range of acrylic colors is more limited, (b) Seeed Studio carries another acrylic thickness, and (c) some people associate thicker materials with ruggedness.
Regarding cases-without-walls vs cases-with-walls...
    This topic gets into the proposed use case for a device that uses Scheme G packaging.
    I believe Scheme G works well for cases-without-walls. On the other hand, the size of the 12-pin shrouded header on the Bus Pirate v4 design means that Scheme G may not work well for this design.
    For cases-with-walls, I believe that the open case design or the modular open case design described elsewhere in this forum thread provide a better solution. In addition, Bus Pirate v4 would work well with these designs.
Regarding the size of the top and bottom acrylic windows...
    I added 2.0 mm to the length and width of the top and bottom acrylic windows that I designed for Scheme G.
    I also increased the radius of the corners from 4.0 mm to 5.0 mm.
    These changes improved the look of the case near the bottom magnet holder foot.
    arakis may have made a different series of choices for his acrylic window design.
dsm wrote:Due to the 1.0 mm magnet holder walls around the 3.0 mm diameter neodymium magnets...
    The normal 3.2 mm mounting holes in the top and bottom acrylic windows are enlarged to 5.2 mm.
    The normal 4.0 mm edge-to-mounting-hole distance is increased to 5.0 mm.
    The normal 4.0 mm corner radius is increased to 5.0 mm.
    The top and bottom acrylic windows are 2.0 mm longer and wider.

I notice in your photographs that you used a right-angle header for the ICSP connector.
Do you like this scheme or would you rather use a straight header and cut out an opening in the top acrylic window?

Thanks for your time.

dsm
Last edited by dsm on Tue Apr 03, 2012 2:39 am, edited 3 times in total.
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Re: Standoff size and side height

Postby dsm » Sun Apr 01, 2012 5:40 pm

thanks

tayken,
ian,

I appreciate the time you took to comment on the example parts that I sent you.
Your comments were quite helpful.
I agree with most of what you wrote and even where I don't agree, I have to admit you make some good points.

I think you and ian were sent "-v2" Scheme G parts.
The neodymium magnets were probably a bit loose and the one-way barb was probably not secure.
I've refined the Scheme G magnet holder designs somewhat and the "-v4" Scheme G parts should
hopefully not have these problems.

Thanks for your time.

dsm
Last edited by dsm on Sun Apr 01, 2012 7:06 pm, edited 2 times in total.
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Re: Standoff size and side height

Postby dsm » Sun Apr 01, 2012 6:48 pm

comments




dsm wrote:Any idea when the new Dangerous Prototypes board templates might be released?

ian wrote:Possibly as early as Maker Faire China in 2 weeks, but more likely for Maker Fair California mid-may.

Interesting. I didn't even realize that there was a Maker Faire in China - although now that you've mentioned it, a Maker Faire in China makes loads of sense. On the other hand, the Make Faire in San Mateo is local for me...



dsm wrote:Did you ever get any feedback from Seeed Studio about how accurately they can route the edge on boards?

ian wrote: ...the tolerance of board dimension is ±0.2mm, and the minimum space from route to the edge is 10mil.
< quoting Dwin >

Sjaak wrote:Sorry man ;) station me over seeed and all you problem (regarding the cases and pcb sizes) are over :D

I don't think that Seeed Studio realizes that they may have a board size problem with their PCB vendors.
±0.2mm board size tolerance would be fine, but Seeed Studio's vendors appear to be consistently out of this tolerance range.
Sjaak makes an interesting point above in that the PCB vendors will only deliver correctly sized boards
if the PCB vendors understand that it matters to the customer and someone is watching (or inspecting the results).

Sjaak wrote:I'm just wondering if 'real' productions runs would be much better within certain tolerances then the 'prototype' runs?

When you meet with Seeed Studio, perhaps you could get them to commit to making the boards as specified.
Since these new Dangerous Prototypes designs will be consistently specified and processed production boards,
it would be worth Seeed Studio's PCB vendor's time and effort to tool up for tighter tolerances.

Thanks for your time.

dsm
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Re: Standoff size and side height

Postby ian » Tue Apr 03, 2012 1:29 am

I notice in your photographs that you used a right-angle header for the ICSP connector.
Do you like this scheme or would you rather use a straight header and cut out an opening in the top acrylic window?


I usually use right angle for development because the PCB sits better (programmer cable does not lift case into the air). One of the things I like about scheme G type cases (without) sides is that I can access ICSP without modifying the case. I am not super partial to either though, and I think most users will never need access to the ICSP.

production versions of each of the designs mentioned above?


I will get them for you as soon as I have access, it's already on my list.

the Make Faire in San Mateo is local for me...


I'll be there :) Tickets are purchased and our booth was accepted to the Maker Faire.
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