Mitochondrion 3.3 Centre Board Redesign

And so, the version numbers tick ever upwards…

It occurs to me that every part I’ve made for the Mitochondrion has, at that time, been the hardest piece of kit I’ve ever made. Case in point – the new centre board. It’s a double-sided circuit board, 14 cm long, 2 cm wide, so the same area as half a Post-It note. It contains a computer about as powerful as a Spectrum, a separate 256k memory, a two-channel audio pre-amp with cross-over and rectifier, a regulated power supply and a battery monitor. And twenty off-board connections. Oh, and there’s a daughter-board taking up 40% of one side. That’s four chips and 35 other parts. Half a Post-It note. Yeah, it’s pretty packed.

I’m definitely getting better at the process. I started the design on tuesday, including picking up an entirely new circuit drawing program (DipTrace, I love you), and the design just needs an hour or so of more tweaking to be done. Then I’ll be spending at least a day checking over the design and modeling/breadboarding the bits that I can, coz I don’t want to have to make yet another. And then buying parts, which will involve me phoning up suppliers and saying:

“A MAX710 in so16 please?”
“How many thousands do you want?”
“Just the one, thanks.”
“Only one thousand?”
“Sorry, no, only one.”
*click*

And then, some time later, actually making it and seeing if my design works or not… But it’s not like the other parts of the Mitochondrion don’t need further work…

The next project is going to involve no electronics at all, just hand saws and hammers. Well, and maybe the Gimp. The next electronics project is going to involve no boundary pushing at all, just bits and pieces that I’ve used before and can put together and expect it to work. Well, and maybe lithium batteries, so I’ll need to investigate better battery controllers. But apart from that, nothing new at all.

*drowns brain with booze to stop all the new ideas*

23 thoughts on “Mitochondrion 3.3 Centre Board Redesign

  1. Sometimes honesty is not called for. Perhaps you have plans to go into series production of Mitochondria in the future? I think the words might be: “I’m thinking of designing in the MAX710 to a consumer electronics item for a client. Can you quote me for 1k, 10k and 100k? And can I get a couple of samples?”

    Meanwhile, my challenge with DDD is to see if I can switch a fairly beefy electric motor without EMI making the computer crash.

    These boys, who seem to be the people for high end switching boards, are pretty firm about inductive loads stuffing up USB. I do however, have an old Gateway laptop that my ex-kitten trashed, which has a serial port, I think.

    Incidentally, if you want me use my limited hardware skillz0rs to review the circuit, I’d be happy to.

    1. Optoisolators?

      My prob is that I’m switching a 10W load in and out in under a millisecond. Not surprisingly, this does bad things to the supply voltage. Hence the regulator for the power to the microcontroller. Frankly, I’d suggest doing this anyway.

      1. Yep, if I have to.

        I think they’ve got some pretty clever (small size, big capacitance) capacitors nowadays? What’s the internal resistance of your chosen battery like?

        1. Dunno, but it’s a pack of 4 AAAs, pretty diddly for that kind of load. Average power is going to have to be lots less than peak power, sadly.

          As for caps, surface-mount tantalums are tiny, provided you’re not fussed where the tantalum comes from.

          1. I know we have Murata 10uF x5r in 1210. I think we have Taiyo Uden 100uF in 1210. And you can always stack ’em if you need more oomph for your footprint. I’ve built mushrooms, where I made a 3×3 stack and put that on top of a single down on the board, when we needed several mF in a small space.

          2. Mushroom? Interesting idea, I’d be worried about the shock resistance. I’m guessing this is not for stuff that gets banged about?

          3. Yeah, not really. If you made a double-wide footprint and stacked two up, that should be pretty immune, but the mushroom thing isn’t a great solution for anything other than bench eval/debug.

      1. Ditto.
        It’s interesting, the politics of sampling. I can request samples from Microchip and get three of anything, every 90 days, but if I tell them I work for National Semiconductor they’ll send me a *lot* more.
        In contrast, if I try and sample Maxim or Analog from work I won’t get anything. They won’t call me back, they won’t even acknowledge I exist, but if I do it from home, with my home email, I get my samples.

  2. I’m way behind in packaging; when I did things, it was on solder-less breadboards, and the weirdest things I had to deal with were 64 pin DIPS.

    But isn’t This that of which you speak, available in quantity 1 for $7.61? Or is so16 different than 16-SOIC?

    1. True, but then again, $25 minimum order and they stung me for $30 shipping costs last time. Convert that into NZ$ and that ends up painful.

      Mouser have no minimum order but don’t stock that part, nor do the two NZ retailers, or their Oz counterparts…

      The actual solution will just involve poking around on the web till I find somewhere that stocks, ships to NZ and doesn’t have a min order. Findchips is a nice idea, but seems to only cover US suppliers.

  3. I got to your journal from the Wellington community.

    I’m pretty new to NZ, so I’m wondering if you are using a local place to get boards printed up? And also, what are you working on? Since I’ve been here, I ordered a bunch of stuff from futurlec.com, which took a few weeks to ship but it was cheap. They don’t seem to have any MAX710’s though. I really wish ordering from digikey.ca for cheap..

    1. Yup, I’m using a local place. It’s my kitchen, coz I’m just printing to transfer film, ironing it across and etching.

      I’ve yet to find a local PCB maker that aims at the hobbyist market, coz I’ve yet to need one. Several of the Australian magazines have talked positiviely about using PCBCart in China.

      For bits, both RS and Farnell have branches here. There’s also Surplustronics and South Island Components, who have less stock, but surprising amounts of things that are popular in this neck of the woods, like Picaxes.

      And as for what I’m making, sorry, but you’ll just have to wait and see…

      1. I’ve heard good things about PCBCart as well. Stupidly, I spent months designing boards using expresspcb (http://www.expresspcb.com/), which is a proprietary thing… so I could only get boards made by them. Next time I do a board, I’ll be doing it with something else (A lot of people are using Eagle.. so maybe that?)

        I don’t have access to hardly anything here, unlike back in Canada when I had a nice basement stocked with parts and tools. I do have access to a few things, like a drill press, on Sunday’s when I volunteer at the bike shop at 128 abel smith.. so that’s come in handy for http://mikebeauchamp.com/building/light-bar/ . I also ordered a few things from a place in australia called little bird electronics, since I couldn’t find anyone in NZ that carries arduinos.

        Sounds like a cool project man… I’d definitely be interested in seeing what you’re making and what you’ve previously made.

        Mike

        1. Previously? I hadn’t done electronics since school. About the only thing I’d point to if I was trying to brag is the carbon fibre unicycle. I’ve been a far too theoretically person.

          I’ve been using Eagle and it’s pretty good. Weird interface to get your head around, but it works okay once you’ve worked out if you should left-click or right-click. The free version only does boards 100×100 mm, which was a problem for me, but it’d be handy for many.

          That said, I’m finding DipTrace easier to learn, but that might be coz this is the second schematic drawing program that I’ve learnt, not coz DipTrace is actually easier.

          1. When I tried eagle, I thought it wasn’t intuitive at all.. and I remember right/left clicking was doing things I wasn’t expecting. Diptrace looks like it’s worth trying for sure..

            the cabon fibre unicycle sounds pretty cool!

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