3d model of motor controller design

I made a 3d version to help me visualize the layout better. It is to scale with all parts modeled. I am able to follow this while constructing my prototypes. I am 95% done building a couple prototypes for the motor controller and plan to test soon. Little LEDs will light up on each power mosfet when it actuates so I can troubleshoot. Plus it will look cool. I'm planning to use a logic level mosfet to drive the main power mosfets. I've seen people do this with transistors to power the main power mosfets so I think the same principle applies to a logic level mosfet to switch on power to the main mosfets.

arduino mega barebones cad design

arduino mega barebones flat flex progress

Above is my CAD model of a Arduino barebones custom microcontroller in 3D and also of my progress so far on prototyping it. Note that I soldered flat flex cable with matching pitch directly to the pins of the Arduino mega microcontroller chip. This will enable me to get the smallest possible microcontroller form factor possible IMO.

Miniaturization is everything for me to fit everything I need to fit in the cramped spaces in my complex robot design. It is actually pretty easy to solder flat flex ribbon cable directly to the microcontroller IC chip once you get the hang of it (but you must wear a visor magnifier to zoom in on it visually as this is tiny tiny detailed work). To do it, you first lay down the ribbon cable and masking tape it down securely, then lay the chip on top and masking tape it down securely onto protoboard so everything is pinned and your hands are free. Then apply low temp solder paste to each pin one at a time with the tip of a exacto knife blade. Just enough paste per pin for that solder joint, not any excess. Then solder one pin at a time by putting a clean soldering iron tip into the little blob of low temp solder paste and dragging the tip away from the microcontroller carefully. You can't hold it on there long, have to just press it in and then slowly drag away and it happens almost instantly. Too much holding it in place creates too much heat which then melts the ribbon cable and the molten cable flows into the solder joint and can ruin the joint by introducing molten plastic into the molten metal. So you have to get in and get out fairly quickly. You also cannot do drag soldering tradition method on all pins as that creates too much heat and melts the ribbon cable. That works on fiberglass boards that don't melt, but a ribbon cable will melt if too much heat gets involved and ruins everything. You also can't use hot air which would melt the ribbon cable before the solder melts - ruining it. So you have to just do one solder job of one pin at a time. I'll do a video on the process and you can see that with the right temp soldering iron (I think I used 500F) and right speed of execution and a bit of practice, you can make the solder joints one at a time without melting the cable at all. The cable you use has to be the same pitch as the thread pitch of the pins so the conduit traces perfectly line up with the pins of the microcontroller.

The ribbon cable comes pre-stripped on the ends so you don't have to strip off the insulation on that end. You just lay it flat and tape it down and put the IC onto it and it lines up perfectly if the cable has the same pitch as the IC threads. But if you mess up and want to cut the ribbon cable and strip the ends and try again (which I had to do before I perfected my techniques and got the hang of this) then you can do so. Just cut it with scissors and then use a nail file to sand the insulation off until some metal starts showing through in some spots, Once you see a bit of metal start to show through, you know it is so thin that you can just scrape off the rest of the insulation with an exacto knife so then you just scratch off the rest with the exacto knife. This too takes some practice and the right touch. When I go to connect the other ends of the ribbon cable to various components and sensors and whatnot, I'll have to make custom lengths for each individual cable strand so for this I will have to separate the strands by cutting them lengthwise with scissors to split them away from the others, isolating each one and then will have to strip off the insulation of each one so it can be soldered to things. The same method as described above will be used for this. Note that for cutting them lengthwise, that is a very precision cut you need. I use titanium straight embroidery scissors for this and of course, as with all the other SMD stuff, I use 8x or 10x or 20x magnification with my visor. This magnification is a absolute must to have any shot at success with any of this imo. Miniaturization is hard to get used to at first, but once you get used to magnification and the eye hand coordination challenges this presents at first, your skill with your hands and precision goes through the roof as the magnification makes you so precise with everything. It's really fun and amazing to see what your hands can achieve with enough magnification and practice!