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Enclosure Concept

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by JonSea, Jul 11, 2017.

  1. JonSea

    JonSea Well-Known Member

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    While I'm recovering from my second knee replacement, I had an interesting concept on creating enclosures without too much effort.

    My designs tend to have a microcontroller board where all the work gets done and connections to the outside world are made and some kind of user interface board with a display and switches, usually connected by an I2C 6-wire interface. I saw an offer for extremely cheap circuit boards and started working on a new general purpose platform to try a few things out. What could possibly go wrong while chewing on pain pills?

    The driving force behind this design is these "Hexalithus Fixed Block Acrylic Link Blocks" from Elecrow. These blocks are a 10mm cube, drilled and tapped for 3mm screws on every face. If a pair of circuit boards is designed with these blocks at each corner, the top, bottom and sides of the enclosure could be made from laser-cut 3mm acrylic. The cost of the needed 8 blocks alone is about US$9, but that's not outragous for a custom-design enclosure with a little style.

    For this project, I'm picturing something like a digital clock. A four digit 7-segment readout, some other indicator LEDs and a few switches on the front panel with the rear panel having various connectors on the back to interface to various sensors or remote boards. It could display time, temperature or other sensor readings. This illustration shows the pair of boards. The control board is nearly complete while the front is just a rough idea so far. I followed Dangerous Prototype's Sick of Beige for the board dimensions.

    Boards.jpg
    I don't envision any fancy interconnect system between boards - just 6-pin and/or 3-pin jumpers as needed. For the 6-pin connectors, I follow Microchip's layout from the PICkit2 programmer/UART tool and the similar Serial Programmer. The function of the port pins varies, but all of my 6-pin headers are:
    1. Port Pin
    2. +5V
    3. GND
    4. Port Pin
    5. Port Pin
    6. Port Pin
    I have to commend Microchip for this screwball arrangement - it seems to handle a reversed connection without harm.

    My 3-pin connectors are:
    1. port pin
    2. +5V
    3. GND
    I believe this agrees with the standard servo arrangement but is at odds with the pre-built DS18B20 probes featuring a 3-pin header.

    With the blocks at each board corner, laser-cut sides, top and board quickly assemble into an enclosure. This picture shows a little style with an overhang around the display to prevent glare, feet on the side panels (since screw heads will be exposed) and extended panels at the back to protect connections. The cubes on the user interface board provide for a transparent lens in front of LED digits or bargrapghs.

    basic enclosure.jpg

    It's pretty easy to expand from here. For example, if upward facing switches are desired (think snooze button on a clock), a third circuit board could be supported horizontally under the top set of blocks. This would also be a good place to use one of those burn-your-eye non-diffused LEDs. A status indicator shining on the ceiling would be easy to see from any place in the room. Using a horizontal board requires repositioning the blocks on the front board but 3mm standoffs will support a lens in their place.

    If an enclosed connection area is desired, a rear panel can be added using tabs and slots in the acrylic pieces to lock it into position.

    Using this method, the length of the enclosure (distance between front and rear boards) can be anything you like. Additional boards may be supported using standoffs on the blocks if desired and the length can be increased to accomodate a battery pack. Compared to standard acrylic tab and slot construction, this enclosure will hold together - the top or side panel may be removed for access without everything falling apart.

    enhanced enclosure.jpg
     
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  2. JonSea

    JonSea Well-Known Member

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    My control board is based on a PIC18F26k22 micro. It includes a CH340G USB chip (handy to be able to talk to stuff with my Android phone!) and a Dallas DS3231 high accuracy clock chip. I've also included a P-channel MOSFET reverse polarity protection circuit to eliminate those "oh #$%@" moments.
     
  3. JonSea

    JonSea Well-Known Member

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    I think this is what I'm going to do for the user interface board. Nothing too awesome here... I'm going to use a MAX7219 to run two 4-digit 7-segment displays. I'm using separate 15mm tall digits (because I have many), with 2 rectangular LEDs for colons in the center of each display. A slight bit of innovation is to steal the decimal point of the right-hand digit to to run each colon.

    To this I'm adding four 12mm tactile switches and four general purpose LEDs, driven from an MCP23008 peripheral driver. It uses a I2C interface while the MAX7219 uses a SPI-type interface, but these will happily coexist on the same set of port pins. The MAX7219 will ignore everything until the LOAD pin is asserted, while the MCP23008 ignores everything not addressed to it, so they are happy sharing the serial interface.

    I'm also adding provision for an ambient light sensor (one of the Radio Shack "Ambient Light Sensor" photo transistors) and for an IR remote control sensor.

    User Interface.jpg
     
  4. dave

    Dave New Member

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  5. Externet

    Externet Member

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    Yesterday I was looking at this clear case alone for $1, cannot find it today, but for sure they have it hiding somewhere. Give it a peek/ re-search

    ----> https://www.aliexpress.com/item/Cle...lgo_pvid=87ef370c-5144-4739-a2ca-1cf41538bae8

    Perhaps can be somehow used in your project.
     
  6. JonSea

    JonSea Well-Known Member

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    I have done many things similar to that with laser cut acrylic. Tab and slots, t-slots for nuts and even plastic clip joints. That can and does work well, but it has a certain look to it.

    I think this method is going to look more substantial; more custom than DIY. We ahall see in a few weeks - my circuit boards are almost ready to be ordered.
     
  7. Mosaic

    Mosaic Well-Known Member

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    Why are those blocks copper? Why not a Plastic or acrylic casting? Seems much more economical.
     
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  8. JonSea

    JonSea Well-Known Member

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    Here are all three boards as I've laid them put. The control board at tbe back is what I originally showed. The user interface board (bottom of the illustration) has two 4-digit displays, 4 switches and 4 LEDs. I had to move things around to get everything to fit.

    I changed the optional top-facing interface board. I was going to use simple port pin interfaces for the switches and LEDs, but I realized adding a second MCP23008 gives me the functionallity at a tiny increase in cost while not using any addotional port pins.

    The boards are in fab now.

    System Boards.jpg
     
  9. JonSea

    JonSea Well-Known Member

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    The last part of this project is laying out the acrylic panels. There is a huge amount of flexibility here. For example, if the top-facing circuit board isn't used, the length of the enclosure could be extended to hold a battery pack.

    This illustration is for laser cutting the various pieces. It's important to remember how the panels will overlap when assembled to get the sizes right.

    The LEDs are behind the transparent front lens. They extend through the top cover. The slot on one of the side panels is for the micro-USB connector.
    Enclosure pieces.jpg
     
  10. tomizett

    tomizett Active Member

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    I'll admit that it's of no particular interest to me personally, but thanks JonSea for putting together such a well written and illustrated write-up on your work. I know that writing long-form posts like this takes time, so credit whereit's due for putting in the effort.
    I'm sure it'll be very helpful to other members!
     
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  11. JonSea

    JonSea Well-Known Member

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    Thanks. These kind of posts don't seem to attract many comments.

    I did make one change to the plastics. I extended the feet a bit and added matching recesses in the top panel. That allows these enclosures to stack if you have several.
     
  12. atferrari

    atferrari Well-Known Member

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    Being so specific they have no appeal to the general public but are precious to those looking "precisely that". And you will make people happy along time.

    Great work.
     
    Last edited: Jul 21, 2017
  13. MrDEB

    MrDEB Active Member

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    Very interesting concept. Question, what program are you using to have plastic laser cut?
    How is the knee coming along? I myself looking to the future knee replacement as well.
     
  14. JonSea

    JonSea Well-Known Member

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    Too precious? I almost feel insulted somehow :) I just want nice looking projects.

    I'm not sure what you are asking. I have my laser cutting done by a local company. Laser cutting is getting pretty common. Trophy shops and hacker spaces are possibilities if there is not a dedicated provider near you.

    If you're asking what program I used to draw the parts to be cut, I use Visio but any CAD program should work. I have even used Eagle in the past.

    Most providers can handle a variety of file types. SVG has been very reliable with one exception. If text labels are going to be engraved, becauss of the way Visio handles fonts, I submit a PDF file of what I need. Text retains the correct spacing.
     
  15. atferrari

    atferrari Well-Known Member

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    For people ignoring everything, a thread like this is a valuable finding.
     
  16. JonSea

    JonSea Well-Known Member

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    Regarding my knee replacememt:

    The first knee was textbook perfect. Pretty much back to normal acter 8 weeks. Walked over 4 milez ome day visiting Vancouver BC at 8 weeks.

    Did the other knee 11 weeks later, 6 weeks ago. It has not gone as well as the first. I have a hematoma in my thigh. It's quite painful and my leg is still swollen. It will extend my rehab by a month or two.

    My recommendation: if you have osteoarthritis of knee and you don't get lasting relief from consevative treatment includimg physical therapy, steroid injections and or synthetic knee fluid injections, schedule the surgery. Surgery is scary. Rehab is tedious but you soon reach the point where there is noticeable improvement on a daily basis.

    If conservative treatment doesn't work, schedule the surgery. The longer you put it off, the worse physical shape you will be at the time of the surgery and rehab will be more difficult.

    Returning to topic...
    .
     
  17. DirtyLude

    DirtyLude Well-Known Member

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    Since I bought a cheap Chinese 3d printer, making up custom enclosures to any size or shape with custom features has been one of its major benefits. I no longer build the project to an enclosure I already have, I build the enclosure to the project.

    [​IMG]
     
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  18. JonSea

    JonSea Well-Known Member

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    As all the pieces start to accumulate, I realized one thing I was lacking was short 3mm screws. Screws will be coming in from 3 or even 4 different directions in to the blocks and they can't cross in the middle! I allowed the screws to penetrate into the blocks about 2mm; 3mm would probably be ok. So, 5mm long screws will handle the 3mm acrylic and 4mm long screws will secure the 1.6mm circuit boards to the blocks. McMaster-Carr has suitable screws in a variety of head styles and materials; I'm feeling cheap today so I opted for the plain steel with Phillips head. I do like black screws but I think the shiny steel will look good with some of the acrylic I'm using.


    screws.jpg
     

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