Sunday, May 25, 2014

1st cut - moving to SMT; getting ready for a short assembly run.

Last week I was busy revising the controller design and moving it to SMT parts.  This is in preparation to having a small run of boards made up, and then machine assemble a large part of it.  Major changes to the design include:

  • Utilized universal Field driver ckt to support 12v-48v, P or N type alternators.  No more need for stuffing options.
  • Also updated the FET drivers for things like starter, glow plug, etc to remove the need for stuffing options.
    Power supply now stuffing free as well 
  • Moved most of the components to SMT, and selected parts from the standard pool of parts at Smart-proto

Overall, most everything has been touched and/or refreshed. The PCB is smaller now, 15x15cm to match a ‘price break’ size for may PCB fab housed.  I looked into going to 15x10cm, but just ran out of edge space for all the connectors… Moving to SMT will allow China to not only manufacture the PCBs, but also do machine assemble of as much as possible. Will decide about hand-soldering through-hole components based on the outcome of the regulators, but it is not too promising IMHO.

Here are three CAD 3D renderings of the PCBs as they are now.

Biggest change: controller board.  Now mostly SMT, except the high power parts.

SO much blank space.  PCB is 15 x 15cm.  I looked into squeezing it more, to perhaps 15 x 10cm, but just ran out of edge space for all the connectors.  SMT stuff is amazing; I even tried to select somewhat 'larger' parts in case repairs, or handwork is needed.  Even so - - - -

Only change for the remote is in the Power Supply side, to match the controller

Notice how the PCB has been sized to match the LCD, no more overhang!

For now I left the remote panel as through hole.  There is only one part that likely will be SMT, as the DIP-8 versions are getting hard to find.  This would mean you would need to solder up the remote yourselves, all the parts as opposed to just a few.  My thinking is:  There really are not many more components that can be put into SMT, the CPU, about a dozen resisters and diodes;  it might not be worth the extra setup costs just for those.

I want to take a break over this weekend from this, and then do a review of the design as well as the PCB layout next week before releasing the revised schematic to the blog.  One thing I need to double check is the heat disbursement;  the SMTs are much smaller in that regard and I need to make sure I am not over-burdening anything.

There is now people interested in 8x of these controller boards, we are looking to do a small PCB run + machine assemble of the SMT parts.   If you are at all interested in joining, drop me an Email.  I figure things will get moving perhaps mid June.

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