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  • Author Author: genebren
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PiCasso Design Challenge - Kinetic Art Mobile - Post 5 - Finally a PCB design.

genebren

Prior posts in the PiCasso Design Challenge:

PiCasso Design Challenge - Kinetic Art Mobile - Post 1

PiCasso Design Challenge - Kinetic Art Mobile - Post 2

PiCasso Design Challenge - Kinetic Art Mobile - Post 3 - Will it go round in circles????

PiCasso Design Challenge - Kinetic Art Mobile - Post 4 - Crash of the Death Star

 

Things have been crazy here lately.  I have been very busy trying to finish out the interior of my new workshop, while attempting to keep my PiCasso project moving.  I have stuck in a re-design cycle, where I have been moving components from board to board, trying to get everything to fit, in a reasonable way.  After multiple re-starts on the design, I think I have a workable design.

 

There are several different requirements on the design that have made it fairly difficult to find the right approach.  Here are a few of them:

  • uniform LED spacing to allow proper illumination of the orb and to allow some 'animations' based on different LED color patterns and sequences.
  • relatively high power (LED and Fan power)
  • fan speed control (based on programmable constant current)
  • BLE transciever
  • Magnetic compass and accelerometer

 

I went through several trade off, trying to keep all of the high speed stuff on a single board, versus the space required for connectors should I distribute the components across multiple boards.  Here is what I ended up with:

imageimage

The Main PCB is riddled with 12 - 0.1" holes to allow additional air flow, through the board, into the fans below (there will also be some airflow around the board edges).  I will be trimming the PCB into a circle, as my PCB vendor (lower cost) only allows for rectangular boards.  The LED boards are sort of a universal design that will be connected to the main PCB, providing pairs of  LEDs along the circumference of orb and a single LED providing downward lighting (right angle mounted, hacked LED PCB).  This will provide me with 18 - fully programmable RGB LED to illuminate the sides and bottom of the orbs.

 

Here are the schematics of the main controller and LED board:

imageimage

image

 

I will need to send these boards of soon and order up parts for the board, but for now, I heading out to the workshop to install drywall and lighting.

 

Thanks for reading along.  I hope that I can get this project moving along a bit faster, so I can meet the deadlines.

 

Thanks,

Gene

Parents

  • Hi Gene,

     

    This is looking fantastic : ) It's nice that you're not afraid to change angles to get your components located where you want them : ) Regarding circle, the low-cost PCB manufacturers seem fine with routing out shapes, e.g. with the mouse-bites, so that could be an option too (i.e. lines on layer 46 in EAGLE). They do sometimes query via an e-mail to double-check they've got it right, so if you're on a timeline that's something to watch out for.

    For the LGA package etc., my pre-heater and hot air tool are underpowered, so recently I've thought about trying low-temp solder paste with it. I don't know if it will work though! I'll try it in a few weeks time, I'll be sending a couple of PCBs to be made in a week or so. The one I went for is called Qualitek Delta 670.

     

    Anyway, it's a really nice design and layout, it's clear a lot of effort went into it! It takes me days to route out stuff tidily.

  • in reply to shabaz

    Thanks shabaz,

     

    I rarely change angles away from 90 degree increments, but in this case, in order to get the LED pointed correctly, I had to do at least the connector at an angle.  Once that was done, it did not make sense to have the connected ICs at a different angle, so they moved too.  It sure is strange routing traces away from the off angle components, back to my normal 45/90 degree traces.

     

    The LGA packages are going to be an adventure.  I has tried some leadless parts in the past, with varying degrees of success, so it is hard to predict how this will go.  I have put some serious thought into getting/building a small reflow oven just for these types of parts.

     

    Thanks again,

    Gene

  • in reply to genebren

    I laid out a 32-pin LGA a couple of evenings ago (some clock part for my old DDS project) and for any 0.5mm pitch although I guess it isn't best practice (I don't know : ( but personally I switch off the tStop and tCream layers, and do them manually (i.e. so that the overall design rules don't apply). That way, I can get a bit of solder mask in-between the pads (although it can arrive broken! the low-cost manufacture seems to not be able to do the mask in-between reliably especially at 0.4mm pitch, but 0.5mm is just-about feasible I hope).

    Like you, I have variable results, I'm confident of the pasting and positioning, but I suffer from low-power heat sources : (

    With the low-temp solder I'm going to try to get nearly all heat from the pre-heater, so that the hot air gun is barely (or not) needed.

    image

  • in reply to shabaz

    Thanks shabaz.  That is a good tip on manually applying the cream/stop to the footprint.  I did a quick update on my PCB to shrink the rectangles to provide a minimal stop between the pins.

     

    Thanks again,

    Gene

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