On Tue, Apr 6, 2010 at 12:56 AM, Sebastien Lelong < [email protected]> wrote:
> Hi Vasile, > > > In 1.c, you say "prepare your mind as the product will be manufactured in > 1000 pieces. In this way you'll avoid a lot of mistakes". Can you be more > explicit about classical/usual mistakes ? Maybe few examples, real-life ones > ? > It's a simple matter of how our mind works. If you (or even me) manufacture one piece of jalluino, and all resistor pads from CAD library have only 1.55mm diameter an 1mm drill size with 0.2mm route width connected to that pad, the resistors can be soldered but the mechanical and electrical joint is compromised (if you don't believe this, take off one wrong resistor an solder again another one). However, since is just one piece of board you'll never correct that mistake because "it works for me" If you think as you'll have to manufacture 1000 pieces, and image you'll have that problem 1000 times x number of terminals soldered, your mind will not let you do such mistake. > > In 1.d, can you give pictures of good and bad PCB designs, regarding ground > & power nets, etc... ? (for the bad ones, you can use mine :)) > This is another article to do. For understanding this issue you need to stay about 1 year on this group and follow discussion: http://www.pcbmatrix.com/Forum/, but this is not enough, you need also to design at least 10 different boards. > > In 1.e, can you tell me (us) more about testing points ? I have indeed > observed these points in big PCBs (DVD players, etc...), and was wondering > how they were used. I guess there's a testing specification document. > Testing points are essential when you have a large number of boards and you have to repeat several times the same measurement sequence. For mass production it's manufactured another board using elastic pogo-pins and the board under test is lying on the testing board, testing points are connected through pogo pins with logic analyzer inputs, scope, signal generator output or whatever. Even when manufacture only 5 boards, testing points are used manually for connecting the tools to the board and are avoiding short circuits you can do on the microcontroller or other components pins (because special micro-grip tools are quite expensive) > In steps you describe, you manufacture PCB before writing firmware. > Shouldn't a (prototype) firmware version be written before ? How do you test > your design ? If not entirely, at least some part of it ? You've now guessed > my question: how do you prototype your project ? > I was prototyping my projects as you do (drilled breadboard by soldering wires) between 10 to 25 years old (I've built my first radio using one Russian transistor at 7) . Once I have understood that only analog stuff needs prototyping (and after getting some experience even analog does not) the software prototyping I do is directly on manufactured boards. But, I'm using flexible schematic designs using zero resistors and DNU (do not use) resistors, stuffing them or not is creating a different hardware configuration on the same board. To people I'm talking with, I suggest to not use solderless breadboards. Why? because correct soldering is an art which can't be learned without practicing. Using predrilled PCB where components can only be soldered and connected only with soldered wires, or wire-wrapping (and somehow positioning them on the board surface is like designing a real board, because once soldered is difficult to take them off, so you'll think twice before soldering...) is the best step for jumping to CAD designed boards. > Or, maybe, what can be prototyped, and what shoudn't be prototyped because > of some hardware issues not compatible with a prototyping platform (PWM with > breadboards, for instance ?) > Partially I've answered you above. Digital stuff does not require prototyping. Analog stuff needs prototyping sometime. RF stuff needs prototyping most of the time, and this is the most difficult thing...because prototyping in RF is about manufacturing RF blocks, testing them separately and connect between them via SMA/BNC/N connectors and special cables. The best rule is reading all available documentation for evaluation modules of an active device used in a project. That is telling you almost all you should need before designing a PCB. > > This actually makes me think about software development methodologies. What > you describe makes me think about the waterfall model: you build your > project as independent steps, when you finished one, you go to the next and > never come back to previous. > If you come back to previous step, it means you have made somewhere a mistake. However even if have years of experience still need from time to time to go back at the previous step. This is named next schematic/PCB/firmware revision. But this has huge costs if you think in the way I suggest (you have 1000 pieces of jaluino on your table and you've messed up your design... what to do?, feel your hair raising up reading the previous sentence? If yes, then you have understood the point. > As a hobbyst and beginner, it's important to have a global overview, the > "big picture", as soon as you can. Test/experiment a schematic, an idea, > from hardware to software, and regurlarly iterate through this process 'til > you reach a point where you're quite confident moving to PCB manufacture is > reasonably possible. It's highly furstrating to produce smoke with a freshly > made PCB you've spent hours on... > No, smelling smoke on a PCB where you've spent hours (better days) is a bless, because will force you to think deeply where you've mistaken. In that way, you can be sure you'll never ever do that mistake again. Is quite difficult for younger people to understand (even for those living in the same area with me), but I always give this example: back in the 80, electronics was a fantastic job in countries under capitalist embargo. Why? Because you was waiting 6 months to get a colour TV and one HV transistor replacement from that TV cost you about 20% from your monthly income. Once the TV damaged, only a few super trained people have the guts of changing that transistor, knowing that even one mistake is fatal for their pocket. Now doing electronics is like knocking nails with a hammer. Does your transistor burn? Yes, take it of and put another one. Does is burn again? Yes, do it again... without asking what the hell is the problem? :) Vasile > > > > > 2010/4/5 vasile surducan <[email protected]> > >> Hi all, >> >> I've wrote a short article with my ideas about designing an embedded >> project. Language may not be the best since English is not my native one, >> however take a look and tell me your comments. >> >> BTW, maybe Seb&Matt will find inside another jallib logo? >> :) >> Vasile >> >> -- >> You received this message because you are subscribed to the Google Groups >> "jallib" group. >> To post to this group, send email to [email protected]. >> To unsubscribe from this group, send email to >> [email protected]<jallib%[email protected]> >> . >> For more options, visit this group at >> http://groups.google.com/group/jallib?hl=en. >> > > > > -- > Sébastien Lelong > http://www.sirloon.net > http://sirbot.org > > -- > You received this message because you are subscribed to the Google Groups > "jallib" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]<jallib%[email protected]> > . > For more options, visit this group at > http://groups.google.com/group/jallib?hl=en. > -- You received this message because you are subscribed to the Google Groups "jallib" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/jallib?hl=en.
