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Wanted info on fabrication of a case/enclosure for an commercial electronics project

Discussion in 'Electronic Design' started by Reza Naima, Jul 3, 2003.

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  1. Reza Naima

    Reza Naima Guest

    Well, after about a year of R&D, a friend and myself have built a
    small device we want to sell to the various niche markets. Now that
    we have the hardware done, we need to deal with fabrication of a case
    for the device such that it looks good and will make the product more
    marketeable. This is where I need help. First off some specifics
    about the unit :

    - Powered by 1 or 2 AAA batteries so it needs to have a battery
    - Needs to be as light as possible
    - Will be exposed to the elements; needs to be water resistant
    - Needs to have an LCD display exposed (if the case is
    transparent, this is a no-brainer)
    - Will have a mini-b USB connector
    - it needs to attach to external sensors. For example, it needs to
    get speed and cadence information from a bicycle. So either we make
    our own sensors and connector, or we have the device compatible with
    existing bike computer harneses. This would require metal contact
    points to be exposed outside of the case.
    - it needs to have 4/5 buttons on the device.

    I really havn't a clue where to begin. We have working prototypes
    that are fairly large, and we can reduce the size and change the shape
    as necessary before PCB production/assembly. However, I'm not sure
    what our options are regarding materials, methods, costs, etc.
    Ideally, I want to optimize on the following factors (in order)...

    1) Cost (we're doing this out of pocket)
    2) Aestetics
    3) Durrability

    Any help would be greatly appreciated.
  2. Paul Rudolph

    Paul Rudolph Guest

    You don't have the money to pay someone to do the work. I'd focus on getting
    the money to have the product development done right.
  3. matt meerian

    matt meerian Guest

    Hi Reza,
    There was very low budget project I worked on earlier this year that
    incorporated two AAA batteries and a USB connector. The enclosure was
    semi transparent blue and the right size to have two PCB mounted AAA
    battery holders inside. (I think it was a Serpac C-4 or C-6 series) The
    only downside to using the enclosure was a single screw had to be
    removed to change the batteries. One thing that helped was placing the
    PCB near where the two halves of the enclosure separated. A hand
    nibbler tool and hole punch was used to make the cutouts for the PCB
    mounted connectors and push buttons. This might be something you could
    do with a "small version" prototype.
    Shameless self promotion: There was a small article I did on a cadence
    counter for bicycles a few years back. It didn't have an LCD display,
    but the data could be uploaded to the desktop computer. See the online
    edition of Circuit Cellar at:
    Good luck with your project.
  4. Rob Campbell

    Rob Campbell Guest


    Please tell me that you've done market research - i.e., identified and
    gained the interest of if not letters of intent from likely customers -
    before doing all this work. If not, you should now, before investing any
    more time and money. misc.entrepreneurs.moderated and are good resources.

    Also, the impression I get from your post is that packaging is an
    afterthought. It shouldn't be, especially for a consumer device and/or one
    that will see rugged use, such as on a bicycle. Even if it's going to sit on
    a shelf and look good, your laundry list of packaging details isn't trivial.
    The R may be done, but the D isn't.

    Sorry for being presumptuous. You may have already done the research and
    thought all these things through.

    Rob Campbell
  5. Ken Taylor

    Ken Taylor Guest

    Ditto Rob's comments. Assuming the best case, look for an off-the-shelf
    package that will do your job, as fabricating from scratch will be long,
    involved and costly. Minimum tailoring should be the goal. There's bound to
    be case or plastics suppliers in your area who can supply you a standard
    weatherproof product without too much drama.

  6. Reza Naima

    Reza Naima Guest

    We've talked to a lot of people and there seems to be sufficient
    interest. We're looking at selling this via word-of-mouth and
    magazine advertisement initially, and if it takes off there, then to
    ramp up production and pursue retail outlets. The largetst
    complication with regards to existing cases is that it somehow needs
    to mount on a bicycle handle. Ideally, it would need to integrate
    with existing harnesses to reduce cost.

    One thought I had was to carve out a rough design in some soft
    material, make a mold of it myself, and use some resins to make a
    small number of cases. This seems like it's the most labour and time
    intensive, but the cheapest option and I dont see why it couldn't

    So far, we've worked primarily on the electronics. But the form
    factor can be any shape now. So I suppose we are now doing that
    aspect of the research.

    Also, as this product will be sold for $300-$400, I just see people as
    being more interested in the product if it looks more "polished" and
    "professional". This is why I am opposed to the modification of
    existing cases idea, as it will not look as "professional". But it is
    worth investigating, so I'll start checking out some suppliers.

    Finally, I called up a tooling shop to see what the cost of the mold
    would be. based on what I described to him, his best guess is around
    $3k for the mold, and possibly $2k if he can use a unit dye (though
    that would limit where I can use the mold).

    Also, does anyone know if it's supposed to be spelled mold or mould.
    I've seen it both ways.

    thanks again,
  7. Marc H.Popek

    Marc H.Popek Guest

    Slightly Off topic... I recently return from a Trade Show IN Philadelphia.
    On South Street Party district, I happenstanced into a no cover bar with a
    Rap group. Now most radio Rap is vile and I don't normally listen to it.
    What I heard that night was wonderful. On tune went something like this, "
    Opinions... everyone's got em.... Opinions... aint facts..."

    and then went onto the story line.....

    There lots of ideas on exactly how a business should run, and given the aide
    range of solution and outcomes,, " Opinions... everyone's got em....
    Opinions... aint facts..."

    Happy selling, sell sell sell that's the focus.

    There are many companies that have plastic work boxes. Good one in east
    coast USA escapes me at present.. sola? They had an upscale version
    of the radio shack boxes. some with battery compartments and others, you may
    have to buy a shell ,and have it "worked" and then use it as your
    housing.... till if ever you tool a plastic mold and customize things.
  8. I may have missed it, but has anyone else in the thread mentioned FCC
    requirements for radio/TV interference? ( Assuming that you're
    targetting sales in the United States.) I thought any digital product
    (barring something with a clock frequency lower than some very low
    number that I don't recall) had to be tested for RF interference before
    it could be sold in any volume.

    Perhaps you've already looked into this but if not, a little research
    now might save some trouble later on.

  9. Khim Bittle

    Khim Bittle Guest

    There is a exception if the unit is battery powered , an unintentional
    radiator ( like this unit ) and is only to be used in moving vehicles
    .... BUT if you take the unit off your vehicle and plug it into your
    computer for download whamo you now have to be tested.

    ( note FCC testing and fixing problems gets expensive fast and it is
    much wiser to carefully package up front )

    You must have the unit tested BEFORE it is marketed ! yup hard to
    believe , the FCC handed out fines at the CES show of $10-20K for
    marketing of untested units.

  10. Does anyone have an idea of how much it costs to test a product for


    Carlos Antunes
  11. Marc H.Popek

    Marc H.Popek Guest

    the testing is relatively inexpensive for fcc filing of simple license free
    (part 15) items, figure 1-3k for the event and the report and filing.

    However, this assumes that your products already MEETs the FCC requirement.
    The testing is only a test and cannot CRWEATE compliance. Compliance comes
    from managing the frequency plan, harmonics, etc.. first to insure
    compliance... then you go to the test range and Verify the you compliance
    and the third party supplies the drat and report. Nice and cozy process.

  12. Reza Naima

    Reza Naima Guest

    Great advice! It's been on the back of my mind to have some testing
    done, but I assumed that it wouldn't be an issue 'till we went fully
    retail with the product. The product already has sheilding on the
    potential problem points (the GPS unit & antenna amplifier). However
    The unit will be plugged into a PC to download data. Does anyone know
    what type of testing is required, how to do it, and how much it costs?
    If it is radiating, can we supply a metal box to put the device in
    when plugging it into a PC? And what about metalic paints? Can I get
    the inside of the case sprayed with such paints to add shielding?
    What's the easiest way to test the unit myself before submitting it to
    the FCC for their testing?

    Also, on the case front, there are some pictures of a laser cut
    acrylic case that looks great on this website :

    I now need to make calls to find out pricing information.

    Thanks everyone for the input so far!

  13. Khim Bittle

    Khim Bittle Guest

    $800 - $1600
    Yes , I have worked with case suppliers who charged $150 setup and a
    couple of $ per piece to spray. Conductive paints have several issues
    including cracking if the plastic case can flex , and flaking of the
    paint over time leaving little conductive particles floating around
    inside the electronics.
    At a minimum you need a good spectrum analyzer and the appropriate
    antenna(s) / lna / cabling ( costing $15-30 thousand $ ) and the
    appropriate knowledge and test space. Antenna must be able to be
    moved and rotated. The correct answer here .... it's time to find a
    local test lab , give em a big hug , tell then you will bring them
    some business and make them your buddy and you will probably be able
    to do some quick checks at a decent price.


    ( obtw ... if you are designing a nifty little gps logging box for
    your bicycle I hope you have reviewed the little garmin bicycle unit
    and others in the pipeline , I only say this because I suspect they
    will sell on the market for less than you can buy your parts for ,
    well good luck )
  14. Ralph Mason

    Ralph Mason Guest

    Well if the product sells for that much, perhaps in the beginning you could
    just buy an off the shelf bicycle computer, remove it's innards and use that
    case. You should be able to find a suitable donor for $20.

  15. Declaration of Conformity
    Same procedure, but there are, as far as I know, now exemptions. But the
    standards and limits against which the device is tested, are roughly the
    same for FCC part 15 class B and the corresponding IEC standards used for CE
    marking. These are IEC 61000-6-3 (compatibility) and EN/IEC 61000-6-1
    (emission). The IEC standards are a bit 'tighter than those for FCC, so if
    you measure for IEC, you're automatically ok for FCC.

  16. RP Henry

    RP Henry Guest

    Why not? I have seen GPS work in my house (wood frame, cement tile roof)
    and in the top floor of a standard So Cal office building (steel frame,
    wood/tar roof).
  17. : Now, our device has a GPS unit in it which might also clasify it as a
    : Receiver, but the GPS will never be used inside home (it can't
    : anyhow..), so I'm guessing (hoping) that I dont need full catagory b
    : testing.

    You could be shocked at what passes category B testing. I sure was,
    most recently with a clone 386 on ISA board with ISM radio, GPS, and
    DC switcher, all in a plastic case with zero shielding and near contempt
    paid towards lead dressing and other normal levels of good hygiene.
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