[font=Georgia:]"clamshell" yaobls case "-v3" update
The "-v3" design "clamshell" yaobls prototype case parts ordered 18Oct11 from Shapeways arrived back 03Nov11. For a list of the differences from the previous "-v2" design "clamshell" yaobls case, see my 14Oct11 posting. I thought that the "-v3" design "clamshell" yaobls parts would be the final iteration before the design was released, but unfortunately... [quote author="dsm"] The current OBLS board layout makes it difficult to design a suitable case because of...
The lack of corner mounting holes (with suitable top/bottom keepout areas for bosses).
The relatively small keepout area around both existing "wing" mounting holes (limits the size of screws).
The position of both existing "wing" mounting holes on the same side of the case.
The LED-to-LED spacing limits the choice of LED lightpipes and attachment schemes.
[/quote] Given the current OBLS board layout, the first and third issues noted above mean that the following change was probably a bad idea for the "-v3" design "clamshell" yaobls case. Sigh... [quote author="dsm"]
The 0.9 mm lip width on both the case-bottom and the case-top allows 0.2 mm (~ 0.008”) of play overall. Based on results from the clamshell-BC-case design, slightly increase the case-bottom lip width to 1.0 mm which will only allow 0.1 mm (~ 0.004”) of play overall.
[/quote] Note that this change would probably the right thing to do if each corner of the case was secured with a case screw (like the clamshell-yabp-case and the clamshell-BC-case designs).
< photos later >
[hr:][/hr:] clamshell-yaobls-case-bottom-dsm-v3 Proposed changes for the "-v4" design include the following:
Restore the 0.9 mm lip width on the case-bottom to allow 0.2 mm (~ 0.008”) of play overall between the case-bottom and the case-top.
Refine the USB-connector-lip-detail and the logic-connector-lip-detail slightly.
Refine the bottom-mounting-hole-boss detail slightly (aesthetics issue - not really necessary).
clamshell-yaobls-case-top-dsm-v3 Proposed changes for the "-v4" design include the following:
Refine the top-mounting-hole-boss detail slightly (aesthetics issue - not really necessary).
I updated the "clamshell" yabp (Yet Another Bus Pirate) case design (see 21Oct11 posting), uploaded the design to Shapeways, and ordered some prototype parts. This case is designed to support Bus Pirate v4.0a boards.
The "clamshell" yabpbottom case can be used by itself to support the Developer use case. The "clamshell" yabptop case can be used with the "clamshell" yabp bottom case to support the User use case.
[attachment=5] [attachment=4] [attachment=3] [attachment=2] [attachment=0] [attachment=1] The four LED light-pipes are assumed to be LPC020CTP parts (data) (Mouser) (catalog). The four case screws are assumed to be 2.0 mm by 6.0 mm T-6 torx head plastite screws from Small Parts (link), but purchased on Amazon (link).
The "clamshell" yaobls case I designed for the Open Bench Logic Sniffer is available on Shapeways (bottom) (top). The yaobls case was intended as a learning experience toward making an injection-molded case for another project. I'm happy about the way the yaobls case is turning out, but the cost from Shapeways is pretty much outrageous [1]. Purchasing the LED Light-pipes and the case screws is a separate cost. Relevant posting thread (link).
There is a preliminary "clamshell" yabp case for the v4.0a Bus Pirate available on Shapeways. What I hope will be the released version of the yabp case should be available on Shapeways in about a week or so. Ditto the learning experience rationale. Ditto the outrageous cost. Ditto the separate costs. Relevant posting thread (link).
Thanks for your time.
dsm
[1] My markup on Shapeways is a nominal $1 - mostly so that Shapeways will keep track and report back to me which of my designs people are buying.[/font:]
The "-v2" design "clamshell" yabp prototype case parts ordered 01Oct11 from Shapeways arrived back 20Oct11. For a list of the differences from the previous "-v1" design "clamshell" yabp case, see my 02Oct11 posting. I expect that the "-v3" design "clamshell" yabp parts will be the final iteration before the design is released.
Unfortunately the v4.0a Bus Pirate board ian was going to send has yet to arrive, so the images use a bare v3.5a-SOIC DIY Edition Bus Pirate board (link). Note that only the board outline and the mounting holes match between these two revisions - all of the connector, LED, and switch positions are different.
[attachment=0] [attachment=1] [attachment=2] [attachment=4] [attachment=3] clamshell-yabp-case-bottom-dsm-v2 Proposed changes for the "-v3" design include the following:
The case-bottom was fabricated in a white polished SLS nylon material which leaves a fairly smooth surface but allows some details to be slightly abraded away. Use unpolished SLS nylon or alumide in the future.
The 0.9 mm lip width on both the case-bottom and the case-top allows 0.2 mm (~ 0.008”) of play overall. Based on results from the clamshell-BC-case design, slightly increase the case-bottom lip width to 1.0 mm which will only allow 0.1 mm (~ 0.004”) of play overall.
Refine the USB-connector-lip-detail slightly.
Refine the bottom-mounting-hole-boss and screw-head-well details slightly.
clamshell-yaobls-case-top-dsm-v2 Proposed changes for the "-v3" design include the following:
The case-top was fabricated in a white polished SLS nylon material which leaves a fairly smooth surface but allows some details to be slightly abraded away. Use unpolished SLS nylon or alumide in the future.
Keep the case-top lip width as 0.9 mm (see above).
Refine the top-mounting-hole-boss and top-mounting-hole details slightly.
Keep the 0.2 mm reveal between the case-bottom and the case-top.
Because the SLS nylon material in slightly flexible, the push-button plunger scheme works well. Based on results from the clamshell-BC-case design, slightly increase the push-button plunger length to approach within 0.5 mm of the push-button (assumed to be an ALPS SKQGADE010 tactile push-button) (data) (Mouser) (catalog).
Based on results from the clamshell-BC-case design, refine the normal-cantilever and reset-cantilever details slightly.
The holes for the LED light-pipes are in the correct position. Based on results from the clamshell-BC-case design, increase the size of the LED light-pipe holes in order to use LPC020CTP (data) (Mouser) (catalog) light-pipes since this series offers more length options. Secure the LED light-pipes with a drop of glue or a retaining grommet.
Currently the space-above-PCB is set to 6.2 mm to allow slightly longer case screws. Based on results from the clamshell-BC-case design, decrease the space-above-PCB to 5.0 mm.
This case design currently uses 2.0 mm by 6.0 mm T-6 torx head plastite case screws. Torx head screws are used since a Torx head is typically smaller than a pan head for the same screw size. While a 6.0 mm screw is a bit too short to hold well, using four screws partially makes up for this deficiency. I suggest that the distance from the edge of the board to the mounting holes should be increased when the Bus Pirate board is updated.
If there are any additional case features anyone wants, please make your suggestions known soon.
[font=Georgia:]"clamshell" yaobls case "-v3" images
I updated the "clamshell" yaobls case design (see previous posting), uploaded the design to Shapeways, and ordered some prototype parts. I expect that this iteration will be the final pass before the design is released.
The case-bottom (link) can be used by itself to support the Developer use case.
The case-top (link) can be used with the case-bottom to support the User use case.
[attachment=3] [attachment=2] [attachment=1] [attachment=0] Thanks for your time.
[font=Georgia:]"clamshell" yaobls case "-v2" update
The "-v2" design "clamshell" yaobls prototype case parts ordered 30Sep11 from Shapeways arrived back 13Oct11. For a list of the differences from the previous "-v1" design "clamshell" yaobls case, see my 28Sep11 posting. I expect that the "-v3" design "clamshell" yaobls parts will be the final iteration before the design is released.
[attachment=4] [attachment=3] [attachment=2] [attachment=1] [attachment=0] [hr:][/hr:] clamshell-yaobls-case-bottom-dsm-v2 Proposed changes for the "-v3" design include the following:
The case-bottom was fabricated in a white polished SLS nylon material which leaves a fairly smooth surface but allows some details to be slightly abraded away. Use unpolished SLS nylon or alumide in the future.
The 0.9 mm lip width on both the case-bottom and the case-top allows 0.2 mm (~ 0.008”) of play overall. Based on results from the clamshell-BC-case design, slightly increase the case-bottom lip width to 1.0 mm which will only allow 0.1 mm (~ 0.004”) of play overall.
Refine the USB-connector-lip-detail and the logic-connector-lip-detail slightly.
Refine the bottom-mounting-hole-boss and screw-head-well details slightly.
clamshell-yaobls-case-top-dsm-v2 Proposed changes for the "-v3" design include the following:
The case-top was fabricated in a white polished SLS nylon material which leaves a fairly smooth surface but allows some details to be slightly abraded away. Use unpolished SLS nylon or alumide in the future.
Keep the case-top lip width as 0.9 mm (see above).
Refine the top-mounting-hole-boss and top-mounting-hole details slightly.
Keep the 0.2 mm reveal between the case-bottom and the case-top.
Because the SLS nylon material in slightly flexible, the push-button plunger scheme worked well. Based on results from the clamshell-BC-case design, slightly increase the push-button plunger length to approach within 0.5 mm of the push-button (assumed to be an ALPS SKQGADE010 tactile push-button) (data) (Mouser) (catalog).
Based on results from the clamshell-BC-case design, refine the reset-cantilever and update-cantilever details slightly.
The holes for the LED light-pipes are the correct size and in the correct position. Use a #38 drill (0.1015") to clean out the holes before inserting the LED light-pipes (LMC020CTP) (data) (Mouser) (catalog). Secure the LED light-pipes with a drop of glue or a retaining grommet (RTN100). The small LED-to-LED spacing of the current OBLS board layout limits the choice of LED light-pipes. This is a problem with this light-pipe series in that it is available in a relatively small number of lengths. The 0.200" (5.08 mm) length is probably too short and the 0.400" (10.16 mm) length is definitely too long. For example, top-wall-thickness (1.5 mm) + space-above-PCB (6.0 mm) - LED-light-pipe-length (5.08) leaves 2.42 mm for the LED-height (0.7 mm) and the LED-clearance. The best long term solution is to increase the LED-to-LED spacing when the OBLS board layout is updated or refactored to allow a light-pipe series with more length choices (LPC020CTP) (data) (Mouser) (catalog).
The space-above-PCB is currently set to 6.0 mm to allow the 8.5 mm high wing connector to protrude from the top of the case by 1.0 mm and to allow the male header pins to be partially protected. Based on results from the clamshell-BC-case design, decrease the space-above-PCB to 5.0 mm.
The choices for the two case screws (currently 2.0 mm by 6.0 mm T-6 torx head plastite screws) are mostly determined by the position and size of the mounting bosses near the Wing connector and WingPwr connectors. For example, width-of-the-boss - (2 * thickness-of-screw-well-plastic-walls) limits the screw-head-diameter. Torx head screws are used since a Torx head is typically smaller than a pan head for the same screw size. Unfortunately, a 6.0 mm screw is a bit too short to hold well. The best long term solution is to provide corner mounting hole locations like the newer Bus Pirate layouts (with enough space for mounting hole bosses) when the OBLS board layout is updated or refactored.
Eliminate the "warning" symbol since it makes an already busy top more busy.
If there are any additional case features anyone wants, please make your suggestions known soon.
I assume Seeed production boards may not need to be limited to the board sizes suggested for their Fusion PCB Service. Also, determining the height of the case is more complicated than it might appear. Various top/bottom case attachment schemes are possible. The design space can get fairly complicated very quickly.
The reason I mention these issues is that some of my recent designs are intended to be the size of a standard 2" by 3.5" US business card - so naturally I think a case to fit 2" by 3.5" boards is a good idea.
I am actually pretty pleased about how the "clamshell" yaobls case is turning out. After the clamshell-yaobls-case-bottom-dsm-v2 and clamshell-yaobls-case-top-dsm-v2 prototype parts arrive back from Shapeways, I suspect there will be one final clean-up pass before the design is released. Working with Shapeways can sometimes be frustratingly slow. If there are any additional case features you want, please make your suggestions known soon.
The current OBLS board layout makes it difficult to design a suitable case because of...
The lack of corner mounting holes (with suitable top/bottom keepout areas for bosses).
The relatively small keepout area around both existing "wing" mounting holes (limits the size of screws).
The position of both existing "wing" mounting holes on the same side of the case.
The LED-to-LED spacing limits the choice of LED lightpipes and attachment schemes.
The current "clamshell" yaobls case is probably getting close to what is feasible with the current OBLS board layout. At what point does it become desirable to update the board layout and/or refactor the OBLS design?
[hr:][/hr:] The layout of the updated Bus Pirate board allows a "clamshell" yabp case that offers similar features (see yabp case thread) to the "clamshell" yaobls case. Unfortunately I am still somewhat unclear about whether I am designing the "clamshell" yabp case with the correct board geometry and component locations.
[hr:][/hr:] Do the Dangerous Prototypes forum pages allow tables in BBCode?
[hr:][/hr:] What about the idea of [quote author="dsm"]Perhaps working with Seeed to get several standard injection-molded cases fabricated would be worthwhile. How about three or four cases designed to fit roughly golden-ratio-sized boards up to the maximum dimensions allowed by the free version of Eagle PCB layout? Seeed could suggest what board sizes would maximize their yield from whatever panel size they use. [/quote] Thanks for your time.
[quote author="arhi"]I for e.g. now found locally some nice aluminium boxes for few euros a piece (for e.g. 75x140x120mm alu box is 5eur and if I want them to cut holes, squares etc in one side that cost 1 additional euro :D )[/quote] Sounds like a business opportunity for you to help your source set up a web store for aluminum boxes. When I used to need small boxes that looked nice, I would buy MicroPak enclosures from Lansing Instrument (link).
[hr:][/hr:]standard plastic case sizes
[quote author="arhi"]Also I mentioned once - it would be cool to get some standard boxes these popular 5x5, 5x20 and 10x10cm boards fit into .. something really cheap SEEED could find[/quote] I made a similar suggestion in the yabp case forum thread... [quote author="dsm"]Perhaps working with Seeed to get several standard injection-molded cases fabricated would be worthwhile. How about three or four cases designed to fit roughly golden-ratio-sized boards up to the maximum dimensions allowed by the free version of Eagle PCB layout? Seeed could suggest what board sizes would maximize their yield from whatever panel size they use. [/quote] But as you point out, ian is probably too busy getting an updated version what he considers to be his flagship product out the door to be interested in this topic right now. Oh well...
What a very cool yaobls tray and yaobls case group picture!
While I am fond of the original yaobls-tray-dsm-v5 design, I like to think that the clamshell-yaobls-case-bottom-dsm design will be better. Unfortunately, as we've discussed before, working with Shapeways can be frustratingly slow and expensive.
Reading between the lines in the yabp case forum thread, ian sounds like he is working with Seeed Studio to get an suitable injection-molded Bus Pirate case fabricated. I went back and looked at the Bus Pirate design and thought of several ways it could be improved. As a result, I hope ian doesn't make the Bus Pirate board and case too small. Two-layer PCBs are roughly $0.50 per square inch in volume, so specifying a larger board shouldn't change the overall cost too much, but a larger board would allow more features in the future. The difference in cost for different sized injection molded cases would also be small (most of the cost is in the mold design and not the plastic).
By the way, do you know whether the Dangerous Prototypes forum pages allow tables in BBCode?
Width Working back though the datasheet, the stated width of the connector is 8.80 mm. The datasheet is inconsistent about the height of the alignment ridges, but use the larger dimension or 9.05 mm. For symmetry, increase the width of the connector to 9.30 mm or 0.366". Subtracting 0.2" for the receptacle envelope leaves 0.166" or an 0.083" offset (which is slightly larger than the 0.080" offset I mentioned) on each side of the receptacle envelope. Alternately, we could use an asymmetric opening with an 0.083" offset on the left side of the receptacle envelope and an 0.073" offset on the right side of the receptacle envelope.
Length Working back through the datasheet, the stated length of the 12-pin shrouded male header is 22.98 mm or 0.905". Subtracting 0.6" for the receptacle envelope leaves 0.305" or an 0.152" offset (which is slightly larger than the 0.150" offset I mentioned) on each end of the receptacle envelope.
Still... While the icconnectors web site does carry a suitable 12-pin shrouded male header, I don't see any prices or a simple way to order small numbers of parts online (unlike Digi-Key or Mouser or Newark). I assume icconnectors (which is based in Taiwan) mainly deals with industrial volume users. While 12-pin shrouded male headers clearly exist, they are still fairly rare compared to common 10-pin, 14-pin, 16-pin, and 20-pin shrouded male headers. Perhaps ian will be able to talk Seeed Studio into carrying the correct connector, but it still seems like an odd connector choice for an open source project.
The holes are in the bottom of the case to reduce costs. One of the really powerful concepts about additive machining is that adding more features and details is less important than the amount of material used. The situation is reversed with subtractive machining where each additional feature and detail means more processing steps (and thus cost).
arhi and I have hashed this "bottom hole" issue out before in the context of the yaobls case. I am less concerned about random metal filings getting into the case than I am about random ESD hits during handling and transport. Once you compare the size of the bottom holes (which are slightly smaller than those in the yaobls case) with size of your fingers, you'll see what I mean. If you really are concerned about random metal filings getting into the case, as arhi points out, you can always add a colorful, high-definition, laminated IO pin reference chart that covers the holes in the bottom of the case.
If someone really needs a completely closed case, deleting the holes and posting another case variant to Shapeways would take me less than ten minutes.
Thanks for your time.
dsm
[attachment=1] [hr:][/hr:] pietja,
I ordered some 12-pin shrouded male headers from the source on eBay that you reference. That source was not able to provide me with a datasheet with mechanical dimensions. 12-pin shrouded male headers are fairly difficult to find compared to common 10-pin, 14-pin, 16-pin, and 20-pin shrouded male headers. Rarity usually translates into higher cost and supply chain vulnerability. Designing a product around lucky eBay finds is generally not a good idea.
Further, there are some interesting functions that could be implemented using currently unused pins on the 64-pin PIC 24FJ256GB106 micro-controller. More functionality for the incremental cost of a few extra pins? Why not?
I looked at a variety of common 10-pin, 14-pin, 16-pin, and 20-pin shrouded male headers from volume commercial sources and then extrapolated to what the dimensions for a hypothetical 12-pin shrouded male header from the same sources should be. Generally the resulting model is to add 0.150" onto each end of the shrouded connector and 0.080" onto each side of the shrouded connector. To this I add the additional connector opening end margin and connector opening side margin mentioned earlier in this thread.
This "clamshell" yabp case design is just a prototype. Making case variants available for whatever size IO connector you suggest is not difficult. This is probably a better solution than adding break-away tabs. My real problem is that nobody has yet specified a part number for the IO connector from a volume source - making this whole "clamshell" yabp case design exercise fairly moot.
I updated the "clamshell" yabp (Yet Another Bus Pirate) case design (see previous posting), uploaded the design to Shapeways, and ordered some prototype parts.
The "clamshell" yabpbottom case can be used by itself to support the Developer use case. See 31Oct11 posting for updated "-v3" design. Features include the following:
Designed to support Bus Pirate v4.0a boards (although it should work with some other Bus Pirate boards).
Bus Pirate board secured between top case and bottom case.
Top case and bottom case secured by four torx head plastite self-tapping screws through bottom case.
Lip detail matches "chamshell" yabp top case.
Improved dimensional model (derived from "clamshell" yaobls case design) for tighter tolerances.
Thinner walls for lower cost.
Openings in bottom for lower cost.
Integral feet.
The "clamshell" yabptop case can be used with the "clamshell" yabp bottom case to support the User use case. See 31Oct11 posting for updated "-v3" design. Features include the following:
Designed to support Bus Pirate v4.0a boards (although it should work with some other Bus Pirate boards).
Lip detail matches "chamshell" yabp bottom case.
Improved dimensional model (derived from "clamshell" yaobls case design) for tighter tolerances. 0.4 mm connector-to-case margin (top, sides, bottom) (USB connector). 0.1 mm board-to-case margin (adds 0.2 mm overall). 0.2 mm top connector opening side margin (adds 0.4 mm overall). 0.4 mm top connector opening end margin (adds 0.2 mm overall). 0.2 mm reveal between the top and bottom cases.
Push-button lever plunger scheme (proposed by arhi) used for Normal and Reset push-buttons.
Commercial acrylic light pipes used for PWR, USB, MODE, and VREG LEDs.
Opening through the top case for the ExtPwr connector. Assumed to be a 2-pin vertical male header that mates to a 0.1" jumper.
Openings through the top case for the ICSP connector. Assumed to be a 5-pin vertical male header that mates to a 0.1" receptacle.
Opening through the top case for the IO connector. Assumed to be a 12-pin (2x6) vertical shrouded male header that mates to a polarized 0.1" 2x6 receptacle. Since 12-pin (2x6) shrouded male headers are comparatively unusual compared to ordinary 10-pin (2x5), 14-pin (2x7), 16-pin (2x8), or 20-pin (2x10) shrouded headers, one option would be to make the opening through the case large enough to allow a 16-pin (2x8) shrouded male header with four pins depopulated to be used. Defer for now.
Thinner walls for lower cost.
[attachment=5] [attachment=4] [attachment=3] [attachment=2] [attachment=1] [attachment=0] Thanks for your time.
[font=Georgia:]more "clamshell" yaobls case comments
arhi,
Thank you for your kind observations.
Pros
The clamshell-yaobls-case-bottom-dsm-v2 is less expensive than the yaobls-tray-dsm-v5 (roughly 75%).
The clamshell-yaobls-case-top-dsm-v2 is less expensive than the yaobls-case-dsm-v5 (roughly 75%).
This design should be capable of being injection-molded (after adding some "draft angle").
Use 2.0 mm x 10.0 mm plastite screws from the bottom to secure the board between the top and bottom cases.
The revised dimensional model scheme seems to work really well. 0.4 mm connector-to-case margin (top, sides, bottom) (USB and logic connectors). 0.1 mm board-to-case margin (adds 0.2 mm overall). 0.2 mm top connector opening side margin (adds 0.4 mm overall) (JP1 to JP6, JP9). 0.4 mm top connector opening end margin (adds 0.2 mm overall) (JP1 to JP6, JP9). 0.2 mm reveal between the top and bottom cases.
Cons
If you want to use the bottom "clamshell" yaobls case alone to support the Developer use case, you probably have to increase the bottom case mounting hole slightly in order to allow an 80% thread engagement fit for a 3.0 mm diameter plastite screw from the top.
The revised dimensional model scheme is overly fussy.
Prototyping the neodymium magnet scheme is difficult with this design (without some post-processing steps).
I decided to not use snap fingers and indentations to secure the top and bottom case since this scheme, although cheaper than using screws, seems a bit dodgy if you are opening and closing the case a lot. I don't think there is enough room for threaded inserts.
