From: machine...@googlegroups.com [mailto:machine...@googlegroups.com] On Behalf Of Bas de Bruijn Sent: March-13-20 6:47 AM To: Jason Kridner Cc: machine...@googlegroups.com; beagleboard@googlegroups.com Subject: Re: [Machinekit] Seeed to design and build Machinekit focused Cape for BeagleBone Black/AI I would use a cape who can drive DC and BLDC motors with encoder feedback. and has room for 24V I/O thru screw terminals. And how many people would be interested in a cape like that? The moment you put one type of driver on the cape you restrict the market. For example the Replicape comes with stepper drivers sized for 3D printers. Try using that on a mill with size 34 steppers or an AC Servo like I have for the 4th axis. The days are past where there is a need or even a desire to close the motor control loop within the trajectory planner CNC control computer. No offense meant to people who manufacture that sort of hardware but 15 years ago the processors to do that were few and far between. Now there are kits like the STMBL which would still be available in its original form had not the motor driver chip been discontinued. A new version is in the works. This drive can do AC servos and DC brushed or brushless. Step/Dir or Smart Serial. And it's small and modular and can be replaced. Yes it's expensive compared to a far east stepper motor driver. A motor such as these types (just an example, maybe different capes for different power ratings) which would make creating tools for industrial situations much, much easier. No need to buy a €250 driver per motor. https://en.nanotec.com/products/2265-internal-rotor-motors/ Such a cape would need to have enough oomph to drive 24V relays, and connect 24V limit or proximity switches. Maybe max out on motor+encoder and have a complimentary cape use the rest for the io’s. The market for such as you describe exists with MESA and external drives using a standard PC. Having hardware that drives these motors would help enormously in just creating a working machine (I’m not looking for 3D printing or CNC myself, but for custom machines) It would help me to focus on creating a machine, and not have me connect a bare BB to an industrial driver. What you want will not be built. The amount of work needed to create something like that for sales in the under 100 units just won't happen. For example in 2016 I created my Electronic Lead Screw project. I included on that board two awesome driver chips that allowed control of a stepper motor up to 3A and 55V. Therefore with a 48V supply one could run 300 oz-in stepper motors. Just the two LMD18245 devices now cost more than an entire micro-stepping driver from the far east. And if someone wants to control both Z and X on their lathe they would still need a second driver. The software inside the ELS has the full micro-stepping code including acceleration and deceleration that now is wasted but I have to maintain it on newer versions for those using the chips. And if someone damages that high current driver I generally have to replace the entire board. The ELS also requires a heat sink if the on board drivers are used resulting in a larger package and since it includes 35 key buttons, an MPG and a display it's not something buried deep in a box behind the machine. So based on my experience I would never again build the motor drivers onto the cape. John Dammeyer Bas
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