A few weeks ago I began the process of re-designing our Syanptron Mega prototype. This is a motion control module based on the Synaptron Micro product we currently sell. The idea was to come up with something a little more powerful, but utilizing the same operating system. We were also trying to keep the cost down, which in this case means frugal use of components and small size.
There’s kind an interesting backstory to this design. We make another product called the Motion Mind 3, which is obviously in its 3rd iteration. The Motion Mind 2 was a design I really liked, and not something I was keen on replacing. However, we had supply issues with two key Infineon parts on the Motion Mind 2. At the same time we had a customer who wanted to use the Motion Mind 2 in an application but required that it be ROHS compliant (basically lead free). The Infineon parts were not compliant.
At the time we decided to meet our customers requirements by converting our design to an ROHS compliant part. We did this by removing the Infineon parts and using discrete components to form an H-bridge. The design has been successful and sales have been good. But In the intervening years Infineon has converted the two parts we used on the Motion Mind 2 to lead free parts. So now the H-bridge (BTM7810K) and the linear regulator (TLE4720-2) are available for lead free designs, and I really wanted to give them another shot.
This is the second attempt at a Synaptron Mega prototype, and may not be the last. In the first attempt I made a concerted effort to reuse most of the Synaptron Micro bill-of-materials (parts list or BOM). At the end of the day I had something that that I could test, but I really felt like many parts were too small, and the board itself was too large. Here are the main changes that were made.
1. Reduce the mounting hole footprint so that it matched a 40mm square cooling fan instead of the original 50mm square fan footprint.
2. Increase the screw terminal connector on the right of the board to accommodate higher currents and larger wires.
3. Increase current and physical size of the linear to allow a little more power dissipation.
4. Increase the discrete component size from 0402 packages to 0603 packages to reduce manufacturing, simplify prototyping and repairs, and to give the small parts a little more mass.
I also had an overall goal of reducing the footprint of the board by 20%. I achieved something in the area of a 5% size reduction. But I like the way this board looks and feels. It’s got that intangible symmetry that I think displays design efficiency.
From a prototype-to-production stand-point this design is about 25% complete. Hopefully building and testing will go pretty fast. I know the first prototype went through about 80% of the electrical testing successfully, and this one will either do the same or fail right off. After that comes minor tweaking of the PCB, re-testing of the design, and the big fur-ball of documentation. If it moves into production then there is a requirement for a production tester to ensure all inputs/outputs function correctly, and some documentation for the test process.
But so far, so good.