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Thread: Another HUD project

  1. #1
    SBOD Pilot Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish's Avatar
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    AP Classic SBOD v. AV1c

    Another HUD project

    When I bought my AP Classic it came equipped with an old Shearwater smithers HUD which, unfortunately, was malfunctioning on channel 2 (would never calibrate).

    I've put up with it, it's still moderately useful as a backup in case the classic handsets crapped out (which never happens, of course, ). But I've felt a little less happy about it since switching to an AV1c controller as now the Shearwater is my only backup in case of AV1 failure.

    Time for something new. I hate the black box and button up behind my head, and I hate that the thing won't switch itself off - I have come back a week after stowing my rig only to discover I've somehow knocked it on as I was putting it to bed and not noticed.

    Alexey's AV-UWT HUD was nice in concept (battery in the HUD) but I'm not a fan of wet contacts and IMO his HUD was way too complicated. I asked if he'd be interested in doing a simplified version but he didn't sound keen at all. Fair enough, worth a try!

    So, the brief:
    1. Keep it as simply simple as possible. No feature creep.
    2. Smithers code (flashes counting up away from 1.0, red for under, green for over).
    3. Increased light output for < 0.45 or > 1.55
    4. Display of power on boot - I don't want battery failures mid dive.
    5. Physical design to include battery in HUD, and nothing but cable back to the head.
    6. Calibration against 100% O2.
    7. I want to know if a channel failed calibration (outside 40..60mV at calibration) at calibration and at powerup, but I don't want a nag flash otherwise.
    8. I want to be able to switch on, switch off, auto switch on when immersed and auto switched off when not immersed after 5 minutes or so.
    9. I want it to be of commercial quality (I design electronic and software stuff for a living, so this means just treating it as a job).

    That list got longer than I liked a lot quicker than I liked, but hopefully it won't grow any longer.

  2. #2
    SBOD Pilot Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish's Avatar
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    AP Classic SBOD v. AV1c

    Re: Another HUD project

    So now that I know what I want, time to try and work out how I'll get it.

    The big design issues seem to be:
    1. Choice of switch (water and touch sensitive, not wet contact)
    2. Getting a battery in there
    3. Not making this thing on my DSV the size of another DSV.

    As it turned out, we were playing with the Silicon Labs Gecko series of processors on another job and I had a look at them instead of an AVR for this. And another look, and another - they kept on looking better. In particular:
    - 12 bit with oversampling to 16 bit equivalent ADCs, NO OPAMP NEEDED!
    - Onboard oscillators for IO and core, NO CRYSTALS NEEDED!
    - Onboard capacitative sensing peripheral, like on your smartphone screen - possible switch?
    - Lots of choices for sleep modes etc to keep power consumption down.

    I dragged out the eval kit and, after a few days of belting my head against the brick wall, had something up and running.


    And it looked like the capsense would work through a plastic case, with a finger touch or immersion equally as well.

  3. #3
    SBOD Pilot Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish's Avatar
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    Re: Another HUD project

    Now for the circle of design hell. Get the schematic laid into the pcb design software, then back and forth with the mechanical CAD for the case and the PCB layout until I found how to fit it all together.

    In the end, I wanted something with as low a visual profile as possible. Just because of the angle of our vision and how exaggerated the things-get-smaller-as-they-get-further-away effect is when it's close to your eyes, it meant a shape within a rough wedge envelope would work. Then making it fit with sufficient case thickness around all the parts, and allowing for a battery cover and the cable and the mounting clip were next.

    Instead of the usual process of making a case, putting a PCB into the case and potting or sealing it, I wanted to simplify things. Keep it cheap, keep it throwaway, and cold cast the case around the PCB so the case becomes the potting on the PCB and cable entry.

    Here's kinda where I ended up with that:


    A few trial runs with the 3D printer in this to see how it would work with battery and cable, eventually I got to a happy place.


    It's certainly a lot larger than the old Shearwater but, from the angle I'll be looking at it during a dive, it's not impossibly large.
    Last edited by Captain Starfish; 7th June 2016 at 00:59.

  4. #4
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    Re: Another HUD project

    Part of this case design came down to the cap for the battery and I spent some time debating options:
    1. AAA battery with cap.
    2. AAA battery soldered in and potted in, no cap, fully sealed, 2-3 years life, throw the unit away (if I could make it cheap enough)
    3. LiIon battery with either an inductive charging loop or a charge connector at the end of the cable near the cells.

    In the end the rechargeable got written off, I don't want to have yet another thing I have to charge between dives and, if it goes wrong, with a AAA I can get one of those anywhere. The full potting option was attractively simple but I had a problem throwing something away just because the battery was flat.

    So I ended up with option 1.

    Cap could be screwed in but, let's face it, that's only to stop it getting knocked out. Once it's under pressure the ocean does the work for us in holding it in place. Working this small, adding a thread would have significantly increased the case size. So I opted instead for a design which uses the o-ring to lock it in place.



    First crack on the lathe (and white cap with the printer). I ended up changing down to a single o-ring for the moment, can add one back later if it fails pressure pot or dive testing.



    Starting to feel like this is happening now!

  5. #5
    SBOD Pilot Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish's Avatar
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    Re: Another HUD project

    Electronics time! Whilst I was mucking about with the case design, I had the PCB off to SEEED (after checking many out, these guys did the four layer board I wanted fastest/cheapest/with the design rules I needed). And wrestled with Element14/Farnell/Newark, whatever they're called in your region, over ITAR restrictions and all that crap to get parts.

    This has been fun. When I'm doing this for work, we get the boards in and put them together with all the parts, then ship it off to a local company to stuff the boards for us. Costs are getting a little out of hand already, so I elected to populate at home. Hah. Drag out the magnifying lamp, the loupe and the hand steadies. This is one of the resistors...



    Shown in the next pic is just the power supply: two capacitors, an inductor (the flat black package down from the soldering iron tip) and a beauty of a chip from Texas Instruments which will give me a solid 3.3V off an alkaline battery all the way down to about 0.7V. Soldering iron tip shown for scale.



    Soldering the Gecko was fun, my first hand solder attempt on a QFN package - no leads, all solder paste and heat gun. But it all worked out so I was pleased.

    Board at the end of my index finger, hard to judge scale but this stuff is small.


  6. #6
    SBOD Pilot Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish's Avatar
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    Re: Another HUD project

    Last step before I make some moulds for the final case is to return to the 3D printer and make some fake cases. I'm glad I took this step because it highlighted some fiddly but serious issues to do with clearance on the battery and terminals, the cable and even the PCB and outside of the case.

    Plus it was a nice point to test the capsense switch, and just hold something that worked in my hand!

    Showing the battery power graph at boot, is full (>1.3V)


    This is one calibration that ain't going to pass, no cable no cells.

  7. #7
    SBOD Pilot Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish's Avatar
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    Re: Another HUD project

    A few tweaks were in order, and had to go round the case loop again. The off-the-shelf battery terminal wasn't going to work so I made one for myself. Involved stripping a battery spring out of a cheap AA battery pack, annealing the spring, reshaping it, hardening it and tempering it. First time I've tried that with spring wire and I was pleasantly surprised by how well it all worked.

    Here it is without the case.

  8. #8
    SBOD Pilot Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish's Avatar
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    Re: Another HUD project

    Now to the final case. A bit of a challenge around that battery spring - I need to somehow block it off so it doesn't get charged with plastic during the shot, but I need to be able to remove the plug I use.

    In the end decided to separately cast a piece that sits behind the spring, then use the insert that leaves the hole for the battery to push up and cover the spring against the cast piece which in turn gets pushed into the side of the main mould. Will see how it goes.

    New resin for me and a long time since I've done any casting, 3d printed moulds which didn't get much finishing work because it's an internal piece. Came out a lot better than I expected. (Piece is the round part between the mould blocks).




    This post catches me up to where I'm at now, still in the middle of designing the mould for the main case. It's proving to be a little challenging with a fairly funky split plane that presently has a couple of overlaps. Hopefully I'll get it done and another update this week.

  9. #9
    SBOD Pilot Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish is a glorious beacon of light Captain Starfish's Avatar
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    Re: Another HUD project

    A lot of quiet views: I should have added, comments, queries, criticisms, suggestions all welcome. I'd rather change things before it gets potted in a throwaway block if I can :)

  10. #10
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    Re: Another HUD project

    Great project.


    Whats the calculated run time/ sleep time of the battery?

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