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Intro to Rough Motor Sizing

Posted on November 17, 2020 by admin

How to vaguely guess the approximate ballpark size of moter required for your application. These are all ballpark numbers, but generally a good starting point for your average motor. Two important parameters: torque and speed. Lets start with speed. This is the easy one: For small inrunners (4″ OD or less), max speed is somewhere around 12k-16k RPM. For Hobbyking inrunners it depends on the quality of construction. For some motors, the magnets will fly off the rotor at high speeds, so probably no not exceed 15k rpm. If the rotor has a carbon or kevlar overwrap (or is an

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Austinshop Pt. 3: The Dig

Posted on November 12, 2020 by admin

Welcome back to the never-ending saga… here we go again. With the epoxy disaster complete, the next thing on the extremely long list was to prep the machines in Saugus for moving. And by prep, I mean excavate. Excavate? Yes, Excavate. The machines were literally buried under about 6 feet of stuff, including hundreds of carburetors, at least 50 truck starter motors, at least 200lbs of NiMH and lead acid batteries, at least 20 small Briggs and Stratton small engines, super old welding gear, about six massive generators, and more heavy stuff. The two photos below were taken after about

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Austinshop Pt. 2: Garage Prep, Epoxy Edition

Posted on October 31, 2020 by admin

Part 2 of the Austinshop never-ending saga. Previous part here. With money down on the machines, I had to find somewhere to put them. Luckily, I just moved into a place with a garage! But, the garage was kind of a disaster. The previous tenant had left a bunch of stuff in the garage, and additionally pretty heavily damaged the garage door on his side. Luckily, cleaning up his stuff wasn’t too bad, and his security deposit went towards buying a new door. The garage, trash removal in progress. Its also worth putting in a picture of the place I

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September 2020: Austinshop Pt 1

Posted on October 29, 2020 by admin

September was a complete ‘unmitigated disaster,’ as Bayley would say. The highlights of September disaster included briefly losing all of my soldering irons and moving into an apartment which hadn’t been cleaned in 10 years. At least its over now, and now we plow into October. Lots has happened. First up, lets backtrack a bit to the events of late August, when I heard about an estate sale from a friend of mine, Nick B. Estate sales are interesting- it is sad that you’re buying the livelihood of the dead, but at the same time, we all will end up

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Lookup Table Interpolator

Posted on August 15, 2020 by admin

Hey y’all, welcome back to my boring blog. This week’s post: LOOKUP TABLES, LOOKUP TABLES, AND MORE LOOKUP TABLES. The IPM current setpoint lookup tables are notoriously annoying to generate because the situation really demands a three-axis table. Speed and throttle position are the obvious axis, but the lookup table is also a function of bus voltage because a higher bus voltage requires less field weakening for a given speed and throttle position. Field weakening more than required is OK, but reduces efficiency for a given power output. Not a huge deal though. On the electric bike, I charge the

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Making a Cutting Board with Aaron

Posted on July 28, 2020 by admin

A few months ago Aaron and I made a nice maple cutting board. It turned out well, and therefore deserves a blog post. I haven’t really done much woodworking, this was definitely my first real woodworking project since high school. All woodworking starts from an average-looking wood blob. However, this block started out special: it was curly maple, which will give the final cutting board a very interesting 3-d looking pattern. Additionally, this wood was special, coming from a tree grown on the farm owned by John Quincy Adams, which is cool. The boards were cut to length and then

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Boating Adventure 2020

Posted on July 8, 2020 by admin

Once or twice a year, something special happens. Something you don’t normally see. Something so incredible, its worth writing a blog post about: The members of MITERS go outside. Hear Ye, Hear Ye: its time for the legendary, certifiably insane, MITERS BOATING ADVENTURE. That time of year when we use our big brains to make magical machines which defy physics by not sinking and occasionally exhibiting forward motion. Usually, every boating adventure revolves around a “main event” of Dane’s creation, such as the Doom-Winch or the boat named Three Wave Rectifier. However, this year a different scheme was proposed: the

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Bad BoatShed with Aaron

Posted on June 5, 2020 by admin

Today Aaron and I made a shed/greenhouse! Last year, Aaron bought a little cheapo greenhouse to store his boat stuff in, which promptly collapsed under the weight of the New England snow. The original greenhouse consisted of a metal frame (which broke) and a plastic covering, which we decided to reuse. We started with a simple CAD model. The dimensions were largely set by the plastic covering. The width was slightly under 10′, and the height was 7′. How high to make the walls was a source of debate. The original plan was to go with a low 40″ wall,

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SSD1306: OLED Screen for Motor Control!!

Posted on May 30, 2020 by admin

A while ago I bought a bunch of cheap 128×64 OLED screens off eBay to attach to random things. They were cool but I never really progressed to using them in actual projects. But in this time of Corona quarantine, I decided to give the screens a go again. It is pretty easy to find arduino libraries for these screens. I wasted no time porting one of the simpler libraries for use on an STM32F401, mostly just changing it to use the mbed I2C calls. This proved to be actually somewhat annoying, but eventually with some aggressive scoping and reading

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STM32G4: CORDIC vs sinf() for Motor Control

Posted on April 14, 2020 by admin

Today I decided to decided to turn on the CORDIC in my STM32G431 and compare its speed at calculating sines and cosines to the sinf() function in the math.h library. I also decided to evaluate the performance of how we can use the CORDIC to more quickly calculate the DQ transforms when doing motor control. First up: evaluating sinf. We declare a float s and assign it to the value of sinf(theta). We measure the time it takes by scoping PA_7. Here is the code: The results of this were interesting. sinf takes a surprisingly variable amount of time to

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