Thank you Michael, this is a promising update and an great yuletide gift. (Not as great as a finished Pyra would have been, of course, but very nice nonetheless!)
Here's a summary of what's left to do:
- Finish the tests of the mainboards and order them (PCB production takes 4 weeks)
- Check if the CPU boards can be further improved and if not, order prototypes for them (PCB production takes 6 weeks).
- Check that the cases are fine and if they are, order them (production shouldn't take longer than 2 weeks)
- Use the current prototypes for CE / FCC testing (planned for January 2018)
- WHILE the bare PCBs are being produced: Check for a whirring noise fix that does not involve using conflict material
- WHILE the bare PCBs are being produced: Design the packaging and material
- Do a test run with the newly produced PCBs and the transparent cases to produce prototypes for the prototype preorders.
- Recheck that everything works fine - then setup the mass production (I'm planning at least 2 - 3 weeks to recheck all of that).
- While that final check happens (or directly after the production of the transparent cases), move the molds to the new company to produce the cases for the mass production.
If I remember correctly, the last time you had PCBs produced they took 2 weeks longer (or so) than expected. I was wondering if the estimates above anticipate a similar delay?
In any case, it looks like Item 2 is the bottle-neck here. After the redesign work for the CPU board is finalised, it will be 1.5 months to produce the prototypes, 1 month for board population, prototype build, and shipping prototypes to testers; x months for testing, and 1.5 months for mass production of the boards (assuming no more prototypes are required.)
The last round of testing of the CPU board took at least 7 months. Supposing that this round of testing could be achieved in a day (zero months), rather than 7 months, it'll be a minimum of 4 months
from the time the redesign is finalised until final boards are ready for assembly into Pyras. [And a minimum of 11 months if the testing phase drags out to 7 months again.]
Given this bottle-neck, would it not be better if Item 2 were worked on
before Item 1. That is, would it not be better if Nikolaus finished the CPU board redesign work so that new CPU board prototypes can be ordered
before he works on populating/testing the main board etc. (or anything else). Or am I missing something here?
Worst case scenario would be we'd have to use a few tantalum capacitors. It would still be A LOT less than used in any smartphone, but I'd still like to find a conflict free solution.
What's your opinion on this?
With regards to the noisy capacitors, I have one question and one comment:
Question: How certain are you that the noise is coming from one of the capacitors for the USB port power? And if so, is it the 100 uF cap or the 22 uF one?
Comment: It seems there are two potential approaches to the problem. Either
1) (If it is even possible, ) change the frequency of the ripple in the circuit (maybe by adding a bit of inductance?) so that it is different from the frequency at which the capacitor vibrates;
or
2) (much easier) use a capacitor with different mechanical properties so that it resonates at a frequency different from that which it experiences in the circuit -- either one of the same physical size but of a different design (i.e. from a different manufacturer), or of a different physical size. Any such mechanical change should prevent the vibration, unless the circuit exhibits a wide range of different ripple frequencies (dependent on load?).
It seems premature to jump to tantalum capacitors when changing to a different ceramic capacitor (or gang of capacitors) will probably work at least as well.
Or if you unplug all USB devices.
