Lecture

Table of Contents

Notes taken during the weekly Lecture held by Neil Gershenfeld.

Week 1: Principles and Practices; Project Management

What Fab Academy is about

  • neil talks a bit about
  • personal fabrication is killer for large-scale digital fabrication. just as personal computers killed minicomputers.
  • seamore: kids in computing
  • now: people are empowered to fabricate stuff theirselves. being self-dependent.
  • future: creating devices, machines to build other machines. being even more self-dependent.
  • even further: assembling and disassembling (see lego)
  • ai revolution: you produce something faster than you. ribosomes make ribosomes.
  • self-reproducing systems
  • john von neumann researched about self-reproducing automata.
  • still in research. but we dont have to wait for that
  • technology we are using will become obsolete, bot the real project we are doing is: if anybody can make almost anything, how will we live, lern adn play?
  • i do not quite understand every thought of neil.
  • more deeply: neil gershenfields episode with lex friedman
  • plus: neil gershenfield: designing reality

Introduction of Other FabLabs

  • Aalto FabLabs: Krisjanis Rijnieks
  • Waag Futurelab: henk
  • creative spark: die sind lustig
  • energy lab ist in togo
  • agrilab: has a farm attached
  • leon: krasse instructors
  • shenzen fab lab: its a whole city. the whole scity is a fablab
  • fablab oulu: student of ferdi

Documentation

  • question in chat: bad documentation?
  • timestamp: 17:22 Ilmenau (for chat messages)
  • reasons
    • for evaluation
    • as a portfolio
    • act of documenting it helps you learn and
    • documentation acts as a resource for futurue generations
  • rsync: low-level file copying
  • talking about git
  • we want you to do personalized websites

Project Management Principles

  • 80/20 principle
  • demand vs supply-side time management
  • triage: there are gonna be things you want to do, but that you just cannot “save”.
    • rather martial analogy: like in war, when there are injured people that will die no matter what comes. you rather go with the people that will survive.
  • serial vs parallel development -> work in parallel
  • spiral development
  • bottom-up vs top-down debugging
  • document and clean as you work
  • dont use instructors to skip reading
  • do oyour own workflow for the week and dont skip any on this important non-technical skills
  • keygen: do not use rsa
    • hank: Ed25519 is preferred for a variety of reasons. You should use it, and no, keygen hasn’t been updated to set it as default (likely to avoid breaking backwards compatibility for people scripting it). RSA is entirely acceptable and has no known security flaws. 2048 bits might be starting to become a bit weak and while the default key size was bumped to 3072 a few years ago, some older distros still default to 2048; you might want to manually specify -b 3072 or 4096 if you want to use RSA.
  • you do not need to document git if you already know it

Week 2: CAD

  • Introducing people
    • luciana (coordination)
    • norella coronell
    • julian (it)
  • image manipulation
  • CAD
    • can be used for 2d and for 3d design
    • constraints…
  • 3D design
    • boundary representation
      • can lead to problems somehow
    • function representation
      • means more computation
    • volume representation (pixels of 3d)
      • needed forreally messy coomplex things.
  • programs. freecad solidworks, etc are all tools he would recommend.
    • Blender
      • there is a cad sketching tool for blender
      • there a cad sketcher for blender. however, it is rough around the edges
      • blender is great at sculpting
      • has a thing named “geometry nodes”, whatever this is
      • like modelling with clay
      • you can do rendering stuff
    • Fusion
      • best integrated in all the steps of design, simulation, path planning, rendering
    • SolidWorks
      • can handle complex designs
      • good tools for life cycle management. tools for material managemnet, sending bills etc.
    • Onshape
      • only in cloud. from ground-up it is collaborative
    • FreeCAD
      • use containers. one can hold multiple parts. you can do operations on the container then
      • …
    • the one tool for frep modelling
      • turned into libfive
  • simulation
    • blender has a nice physics simulation. do not build an airplane with it, but iyou can do chains and stuff
  • video/audio
    • stay away from gifs other than a few frames
    • kdenlive
  • AI stuff
    • see link
  • LLMs with CAD
    • does understand how to use CAD, but has no understanding of geometry nor of physics.

Questions

what 3d rep is used in common cad tools?

what is this imperative, declarative, generative, optimization, … etc in the notes?

For moving from one app to another, what considerations are there for file formats? - Benedikt: normally I use .step for 3d models because they are actually 3d models, not only meshs like .stl for 2d files .dxf works for me really well but .svg are also powerful. I prefer .dxf because the integration in Inventor and Fusion is a lot better than .svg.

Would you recommend me to still look at some commercial software? If yes, why? I am thinking about maybe looking at only onshape, blender and freecad. - recommend trying them and understanding what the differences are among them - this actually is the assignment

Ferdi’s Addendum

  • regarding the website: most of the other used mkdocs. works quite nicely
  • i do not have a specific idea for my final project yet. what do i do?
  • talks about evaluation
    • there is gonna be a mid-term review. that makes it easier for us.
  • todos for next week:
    • be able to do parametric design
    • you want a cad software that
      • is “feature”-based
        • everything you do (round an edge, extrude) is saved separately from the object. you can change that. blender is not entirely feature-based
      • you want csg: constructive solid geometry: you will never see the “inside” of a sphere. it is not possible to “look inside”
      • should have a history or a tree of operations
      • you want the software to be parametric, that is you can change parameters later on
      • associative: you want to be able to add constraints
    • problem with freecad is: topological naming issue. however, you also have that in professional software.
  • big players:
    • cadja, siemens nx, creo
    • those have smaller brothers:
      • cadja -> solidworks
      • creo -> solidedge
      • fusion360 -> inventor
  • for linux users it is a bit a struggle
    • freecad is an option
    • onshape is an option
    • xdesign is an option
    • solvespace is an option (although freecad might be better)
  • what would you recommend to model for this week?
    • would be nice to try out assembly features

Week 3: Computer-Controlled Cutting

  • compression

    • do not commit .mov. they are not web standard. commit something else
    • h265 is compressing better than h264 but not widely supported in web
    • using zip just to compress files is fine.
    • if files get very big: do not upload them in git. it is fine to host it externally and put a link for where you are hosting that

  • vinyl cutter

    • applications
      • vinyl:
        • pcbs
        • cutting copper
        • tshirt customization
        • stickers
        • …
    • issues:
      • set force, speed, depth the blade goes in. all of that depends on material, humidity, etc.
      • set a vinyl cutter requires skill
      • you can hold things in place by
      • weeding: remove the stuff you dont want. that takes the real skill

  • laser cutter

    • applications
      • halftoning
      • pressfit construction
    • kerf the stuff that gets cut’ away
    • you need to think of that during constructing
    • materials
      • cardboard
        • bad cardboard when you bend iit, it kinks
        • good cardboard makes a smooth bow
        • good cardboard: heavy duty shipping cardboard
      • pasta
      • fabric
      • wood
      • acrylic
        • cuts easily, high resolution, cracks easily. not touch
        • good for displays
      • acetal/delrin
        • doesnt cut as clean, but is tougher. if you drop it it doesnt crack, it just deforms
        • good for use joints, moves…
      • there are some differences in delrin and acrylic
      • dont cut pvc when you dont know where it comes from!

  • pressfit construction kit

    • joints
      • simple one
      • champher
        • always do this. it is easier to align parts and compresses the cardboard parts
      • this ^ is a hierarchy of stronger and stronger joints
      • if you want to have kids play with this you just need a chamfer
      • finger
        • dont really hold well
        • but good for kids playing they do not need joints so strong
      • snap is better for stability
      • if you have something that is supposed to bend, make the point where it meets the body stronger. to reduce stress
    • you can also curve 3d shapes from something 2d
      • if you make a beam and you bend it

  • this weeks rehearsal:

    • what is programming
    • how to get stuff into chips
    • how to debug?

Ferdi’s Addendum

  • document whoever is speaking and a picture of whet they producd in the week.
    • maybe a name, a link, a description
  • lets meet every thursday at 9
  • preliminary to tomorrow:
    • everybody does safety stuff
  • tomorrow:
    • 1h lecture on laser cutting plus additional information
    • afterwards, intro to lasercutter
  • from now on we meet every thursday from 9:00 to ???
  • nesting: act of arranging pieces on a sheet so that everything is layouted perfectly (material efficiently)
    • deepnest is a software that does that for you
    • however, ferdi says that you can do it yourself also pretty good.
  • kyub: software vom hpi
  • minimum assignment:
    • karton dass man zusammenstecken kann
    • gruppenassignment
    • sticker schneiden

Lasercutting (Ferdi)

  • nice tools
    • cuttle
    • flatfab
    • thenounproject for symbols
  • if you are looking for vector graphics, using fonts is always nice. lazer consists of tube filled with co2. on one side there is a mirror with a whole inside. on the other side, it is open.
  • what you can do with a lazer that you cannot do with a milling machine:
    • engraving
  • 3 types
    • 3o2 laser (unikat)
    • there are dc and ac lasers
      • dc lasers have a glass tube
      • ac have metal tubes
      • regarding the tube: if you replace it check that there is no leak
      • lasers degrade slowly. with the time its power decreases, you need to reduce the speed with the time for the same results
      • dc laser can burn a little whole or not when you engrave. the really cheap chinese lasers cannot do halftone.
    • diode laser
      • small, efficient
      • dont have so much power.
      • come in different frequencies. lot cheaper. last lot longer
      • frequency range is different
      • with most of them you cannot cut transparent acrylic
    • fiber laser
      • like diode lasers. you send your light in a fiber.
  • different options for halftone:
    • stipple
    • …
    • work in different patterns, but result in similar …
    • circles arranged in diagonals, in grid, randomly placed.
    • our laser can only make dots of one specific size. we can only vary the density of the dots. not the thickness
  • beds:
    • honeycomb: problem: when your cardboard is not perfectly flat. gets bend
    • stripes of steel or L profiles (you can clean them and if they break, you can cut new ones)
  • air assist: air is blown through somewhere near the head. to blow out the flame.
  • cleaning
    • use lint free wipes (optics store)
    • there is cleaning liquid which is expensive. however, it smells just as contact lense cleaning liquid.
    • dont rub. lay the wipe on the lense, let it soak in and pull it off again.
  • restrict on cutting PVC
    • there is an instant headache. it emits gas which transforms to HCl in your body.
    • there are tests for pvc
  • if you just laser something, inside fills with smoke. wait 5 seconds while the smoke is ventilated.
  • do not stare at the laser
    • this hurts your ieys
  • make sure, the laser is closed. if you can look through the gaps and see the laser, thats not good.
  • normally u do not use glasses. however, our laser does not close properly, so we need to do that.
  • dont move it before you are sure it is cut.
  • another topic is gonna be how to get files from computer to laser
  • if something sounds bad, stop everything immediately.

Student Reviews

Week 4: Embedded Programming

  • Intro
    • everybody now has a global evaluator. the global eval is not only an evaluation but its also a person to talk to when there are problems and they help you to fulfill fa standards
    • there is a schedule for it 
       1February 12: global eval started
 2March 9: US Daylight Savings Time
 3by March 1: student+local+global intro meetings
 4April 9-23:
 5    - break, midterm
 6    - preceding weekly assignments due
 7    - student+local+global review meetings
 8    - review assignments and final plan
 9    - sort into likely/possible/unlikely to finish this cycle
10June 4: weekly assignments due
11June 9-13: final presentations
12June 16-20: student+local+global review meetings
13June 23: global eval decisions deadline
14July 4-11: FAB25

Lecture

  • organizational
    • this time we do it a bit - this time we do it a bit different
  • in the lab we are gonnaa demonstrate with the processors
  • then we will program using a simulator
  • only then we are fabricating
    • in the lab we are gonnaa demonstrate with the processors
    • then we will program using a simulator
    • only then we are fabricating
  • first thing to do is choosing the architecture: von neumann vs harward
  • risc vs cisc?
    • RISC focuses on simplicity and efficiency, with a small and uniform instruction set that is easy to pipeline and fast to execute.
    • CISC uses a larger, more complex instruction set, enabling fewer instructions to perform complex tasks, but with a trade-off in terms of execution time and pipelining complexity.
  • harward vs von neumann?
    • Von Neumann is simpler, has shared memory space for data & instructions; Harvard is more complex, data & instructions use separate memory space, making it more difficult to implement but faster (can access data & instructions simultaneously).
    • Choice depends on your applicaiton needs. Choose based on which mcu family you prefer, e.g. avr, arm, esp32, etc. Instruction sets are similar across families and you can ge mcus with different amounts of memory, pins & peripherals/features.
    • Most programming done in high level, so the architecture is transparent to the programmer.
  • multiple types of memory
    • SRAM (fast)
    • DRAM (big)
    • EEPROM (non-volatile)
    • FLASH (programs & strings)
    • fuse (configuration)
  • there is a lot to learn, we dont start from scratch. neil gives us examples
  • we dont need to start from scratches.
  • as we progress we need to know all of this
  • word size
    • what is a word? fixed-size unit of data that a processor can operate on in a single operation.
    • example: 8 bit processor can handle same data, just takes more time
    • you can use that using just more powerful prowessor (more fast)
  • pi calculation benchmark
  • how it all works
  • different families
    • AVR
      • What makes it special? …
      • they are nice to embed
    • ARM
      • compared to AVR, arm family are 32 bit
      • somewhat faster clock 48Mhz
      • more kinds of peripherals
      • even smallest one knows how to speak to usb
      • harder to program
      • code is bigger. you need larger programs to program them
      • however, they go up to the processors in superwcomputers/ in phones
      • you use them when you need to go to more povwerful programming interfaces and peripherals.
      • D11C, D11D, D21E, D51 are a single arm family, but the different Ds just say how many pins your chip has
      • STM32 ui dnt know
      • rpi …
      • rp2350 …
      • for most powerful embedded processing: need raspis
      • there are all differen tprocseses
  • octopart: search engine for parts
  • packages:
    • dip (dont use that anymore)
    • surface mount is the way
    • tqfp, lqfp for very small spacings
    • MLF, WLCSP, … for very very small
  • so we chose a package and a family. now: code:
    • we dont start from scratch. we take templates
    • you can use c/c++
      • fast, efficient
    • rust
      • more safe
      • you can use it in embedded, but rust tools are much less supported. there is much more you have to setup.
    • python
      • you can use python also for embedded. you can express much more with python with less python code
      • it is slow. it takes space
      • it is nice to handle however, especially when it comes to math
      • see software benchmarks!
  • in-system development
    • you need bootloader
    • whiy? …
    • jtag programmer for putting it on some microchip. probably some standard
    • …
  • development environments
  • operating system
    • bare-metal vs cooperative vs preemptive multitasking
    • operating systems can be used to run programs in parallel on the same microcontroller
    • however, it might be better to have no OS and have different processors for each process
  • shells
    • μC, but inside a nice enclosing with a usb and the pins led out for easy access
  • usb
    • if a μC “speaks usb” that means that the hardware for handling USB is there, but you need to include usb standard in your code with library
  • AI with μC
  • debugging and simulation
    • wokwi
    • For Newbies you can use tinkercircuit which does allow you to use multimeters and the led do blow up :0 this good for just getting started you will need to move to wokwi
    • AVR8js is very nice for mixed signals

Ferdi’s Addendum

  • option to have class in bigger classroom?
    • yes why not
  • tomorrow at 9:
    • we all would be terribly bored with an arduino intro class
    • arduino intro
    • we should have a look at the few available microprocessors
    • make a plan on what we have to do for the group assignment
    • social modia appointment
  • available boards
    • xiao
  • we will use the rp2040 a lot
  • yes, we really should read all the manual

questions for ferdi

  • which boards do we have?
  • differents microprocessor & microcontroller?

Student Reviews

  • Yuya Tokuyama
    • Yume Ga Arukara: best ramen in america
    • E-Ink was invented in neils lab
  • charlotte latin
  • how big is a video allowed to be?
  • Benedikt!!!!!!
    • wants to work with neopixel leds
    • the rp2040 you somehow have multiple processing units you can program. you can program the rp2040 to make custom peripheral with the PIO. to use with eg ws2812 leds.
    • issues with wokwi? sometimes compiling servers were shut down
    • note for arduino flavoured code: avr8js
    • led underneath thinned wood
      • the wood glows through it beautifully
    • duct tape has a half life
  • fpga vs mc?
    • 2 ways to use fpga:
      • need performance that goes beyond the processor

Week 5: 3D Scanning and Printing

Lecture

  • limitations
    • open materials are affordable
    • “better materaials” are expensive
  • materials
    • see material tables of eg prusa (links on page)
    • pla
      • plant-based
    • petg
      • oil-based, recyclable
    • wood filament
    • metal
    • hygroscopic absorb moisture. you need to dry it. otherwise it will decrease print quality
  • parameters
  • design rules
    • supports in the print
    • 3d printed fabric by not giving the print enough material
    • overhangs
      • 30 deg angle you can brint without supports
      • shorter overhangs can be printed without support
    • bridging works without supports due to tension
    • there is a limit on how thin a wall can be
    • structural properties are anisotropic due to layering.
    • surface finish is function of angle
    • infill
    • avoid sharp corners. we want to have a fase to have anough filament at this place.
  • finish
    • there is a coating to smoothe a 3d printing bath
    • electroplating
  • different techniques for printing
    • stereo lithography etc.
  • different companies/initialtives etc.
    • reprap
      • print printers yourself
    • prusa
    • Bambu
      • difficult to change things
    • formlabs
    • open source machines
      • inmachines
      • hangprinter. print large things in large space
      • e3d
      • precious plastic
      • filastruder
  • funny things
    • 3d print on fabric
    • 3d prints of images
  • food
    • food-safety. you have to
  • formats
    • stl. list of triangles. can be ascii. almost always its binary
      • write algorithms that write stl
    • amf, 3mf
      • not A standard, a shoebox of many standards. still evolving
      • handles splines, frep etc. container that can plugin all different descriptions
      • package of formats. thats the bad about it
    • voxels
      • cannot be handled by printers
    • g-code
    • some other weird sdadards
  • advanced stuff
    • arc overhangs, etc
  • software
    • meshlab for editing and cleaning up scans
    • slicers
      • …
    • printrun for running prints
    • octoprint running print farms
  • scanning
    • tomography (gold standard, very expensive)
    • …
    • pour liquid over item. scan ow the oject disappears
    • digitizing arm. selectively take the points that are important.
    • photogrammetry
    • low cost scanner: creality
    • scanning people
      • baking flower or talcum powder helps scan hair
  • ideas
    • print only infill
    • print weird ai-generated 3d objects

Ferdi’s Addendum

  • 9 uhr donnerstag
    • ferdi wird über 3d druck erzählen
  • wir machen donnerstag das group assignment

Intro 3D Printing by Ferdi

  • stereolithographie:
    • 2 laser beams into a liqueid. liquid gets hard only where two beams meet each other
  • ferdi talks about 3d printing back in the days
    • some projects
  • corexy is a method to move something in 3d space. alternative is hbot. how to draw rubber bands. problem with hbot: verzieht die gantry .
  • mtm.cba.mit.edu
  • ilan moyer: erfand shaper
  • nadja: erfand irgendwie druckköpfe ablegen
  • beide erfanden: popfab. drucker den man in koffer packen kann
  • was es noch gibt ist foldarap
  • beide sind nicht verkehrt. könnte man kleiner und kompakter machen
  • another printer that ferdi built: yarr
  • scanning with milk. you can make pictures, upload to fabmodules and render a model from it
  • photogrammetry is also a thing
  • structured light scanning
  • nerf is also a thing
  • printing
    • fdm (fused deposition molding): stratusses was one of the market leaders together with 3d systems. there fdm name comes from
    • fff (fused filament fabrication): open source version of it
    • sls (selective laser sintering)
      • you have powder and you laser the powder until it melts
    • sla (selective laser …) same thing but using a projector
    • stereolithography
    • printing clay with metal and then remove clay in oven
    • neri oxman
  • codethread: library that generates gcode from tiago
    • print only strings
  • lets schweiß together!
  • topopt
    • opology optimization
    • building lightweight structures
    • you can transform models to use less material which always looks cool

Review

  • Sierra Nieves
    • art therapy project
  • Albert
    • statistical geneticist
    • persi diaconis: mathematics of shuffling cards
  • [Florimond chu]
    • fablab singaopore
    • design trained
  • [sharvari]
    • furniture design student
    • chainmail in blender
  • [anna from iceland]
    • likes light sabers
    • fab saber is a project neil recommends
  • [julian boßler]
    • chainmail, joints, coins, in-place
    • chainmail kreisel
  • akash edamana
    • fidget toys!
  • […]
    • nice voronoi balls

Week 6: Electronics Design

Lecture

  • see assignments:

    • adrian
    • picture
    • annealing pcb

  • wires

    • specified by AWG. specifies how much current it can handle. search for “wire awg”. there are corresponding tables
    • when wires need to be removable. there are connectors for that.

  • buttons

    • normally open, closed when pressed

  • switches

  • resistances

    • R = U/I

  • capacitors

    • C = Q/V

  • crystals

    • devices we use to tell time

  • diodes

    • protect your circuit from not getting killed by wrong polarity of battery e.g.
    • mnemonic: current goes from “A” to “C”. Anode to cathode. alphabetic order

  • zener diode

    • precise voltage reference.

  • mosfets

    • bipolar transistors
      • we dont use those
    • mosfets
      • we use those
      • you can use this to even switch powerful currents
    • P-Mosfet
      • source of current
    • N-Mosfet
      • sink of current
    • a mosfet cannot do both.
    • a mosfet has a gate, a source, a drain.
    • variable resistor where the gate controls resistance
    • we can use that for being either all the way on or all the way off
    • reason: rds: resistance between drain and source. you want this to be small
    • P = I^2 * R
    • we want mosfets with a low gate veoaltage so they are easy to turn on and off
    • we want mosfets with a low rds to not consume too much power.
    • chatgpt on rds: 
       1The **Rds** parameter in a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) refers to the **drain-to-source resistance** when the MOSFET is in its **on** state (also called the **"on-resistance"** or **Rds(on)**). It is the resistance between the drain and source terminals when the MOSFET is fully conducting.
 2
 3### Key Points about Rds(on):
 4
 51. **Low Resistance when On**: When the MOSFET is turned on (i.e., when a voltage is applied to the gate that allows current to flow from the drain to the source), Rds(on) is a measure of how easily current can flow through the device. Ideally, this resistance is very low, allowing high current flow with minimal voltage drop.
 6
 72. **Impact on Power Loss**: Rds(on) contributes to **power dissipation** in the MOSFET, and this dissipation is proportional to the square of the current flowing through the device:  
 8   \[ P = I^2 \times R_{ds(on)} \]  
 9   This means that if Rds(on) is too high, it can lead to significant heat generation and inefficiency in power electronics.
10
113. **Gate Control**: The value of Rds(on) is influenced by the gate-to-source voltage (Vgs). A higher Vgs (within the specified operating range) typically reduces Rds(on), making the MOSFET more efficient for current conduction.
12
134. **Temperature Dependency**: Rds(on) can increase as the MOSFET heats up. So, high power dissipation can cause thermal issues if not managed properly.
14
15In summary, **Rds(on)** is an important parameter because it directly impacts the performance of a MOSFET in terms of efficiency, heat generation, and current handling capabilities. Low Rds(on) is generally desired for high-performance applications.

  • regulators

    • ??? TODO

  • op-amps

    • amplify things

  • microcontrollers

    • for this week we need to be aware of is the pinout.
    • each part has a table where the pinout is written.
    • protocols
      • i2c: talk between processors
      • uart: talk to computers
      • spi: another protocol
      • qtouch: protocol for sensing

  • design circuits

    • art of electronics
    • electronic design automation

  • design rules

    • for how skinny a wire can be, how close they can be together etc.

  • tinkercad, … etc do nice things but do not do everything we need. not recommaended

  • KiCad is recommended

  • part libraries

  • using kicad

    • wiring up
    • pcb editor: layouting
    • setting a boundary for the board
    • viewing the pcb in 3d
    • footprint and 3d model are included in the library
    • you can export the 3d model to use in cad software
    • not quite as integrated as other tools, but very powerful
    • other features:
      • push routing
      • autorouting
      • autoplacing? kicad can also autoplace. hesitation is when you are doing a giant board, you really need auto-placement. on smaller boards (what we do) it is a hard problem to do well. then, it would be a messy design. still, neil has no tools to recommend that would be better. it is continuing getting better.

  • eagle is another software

  • libraries

  • when you design circuits, you use verilog and/or vhdl. not recommended for beginners.

    • for many purposes it is quicker to descrbe relationships etc.
    • you do this for circuits whose layout is rather algorithmic where clicking and dragging would be too much work

  • svg-pcb: another pcb tool

  • simulation

    • spice (ltspice, ngspice, …)

  • debugging

    • check voltages
    • check oszi/logic analyzer

  • use logic analyzer to decode protocol

  • personal assignment:

    • go through all in/output devices you want to use and be able to communicate with them. and start working with that.
    • main goal: get going with an eda tool. started.
    • it is harder than other tools. however, the tools are worth it.

Ferdi’s Addendum

  • you are free to use any eda you want. ferdi recommends kicad
  • if you are comfortable with any other one, check if you can find the libraries. having the fab library available is helpful
  • start thinking in thou (or mil): 5 thou = 0.005 inch = 0.127mm
    • just need a rough feeling for it
  • now everything is 2d
  • when routing power
    • consider routing following tree structure so that traces do not get too hot (reduce current going through each trace).
  • when routing signals
    • do not use tree structure! signals are of low power and you want to maintain it.

Review

Week 6: CNC stuff

  • shapers are useful for create fine cuts and you can take them whereever needed
  • materials
    • trifold cardbord. you can even use this to make furniture. recycle- and renewable
    • plywood
    • mdf. worse structural properties. there is resin in there, fiber etc. its heavier, not as robust. however, it is nice to fabricate
    • mdo. best of both plywood and mdf
    • osb.
      • thickness is very unpredictable
    • garolite.
      • easy to machine
      • very stiff material
    • …
  • vendors
    • what they consider scrap could be the resources for your project
    • wherever on the world you are, you should find out who your vendors are
  • tools
    • …
    • ceramic layer on the tip of the tool increases the lifetime
    • coatings will depend on the material you’re working with. Coatings containing aluminium can cause problems when cutting aluminium for exemple.
    • up cut vs down cut
    • other end mills:
      • ballnose endmills
        • note about ball end-mills, a very good portion of cheaper ball end-mills don’t really have a predictable radius at the tip so dimentional accuracy isn’t guaranteed. for mold making if the ball tip is very small it doesn’t matter as much.
      • extra long endmiils. thinner. need to go slowly
  • speeds and feeds
  • cut depth
  • lubricating
    • removing heat from cutting
    • …
    • you dont use lubricants with wood. typically with plastic. only needded for heavy metal machining. light metals also do not need lubricants as well
  • fixturing
    • vises
    • bar clamps
    • screws
    • …
    • vacuum bed
      • this is preferred in a jobshop. fast to produce things with them. however, they need maintanance
  • sacrifical plate
    • you mill the whole plate. idea is to have a plane layer relative to the machine
  • making plywood foldable
  • joints
    • japanese joints
      • different ways to hide a joint. different variants of how to transfer forces
    • in laser cutting neil showed some joints already.
    • one of the nicest joints for this week is the wedge joint.
      • advantage: you do not need to know the thickness of your stock exactly
    • maxwell criterion: if there are more degrees of freedom than constaints, the thing moves. you have to add constraints.
  • how to machine
    • consider runout of the tool. its about how big the stuff is that is cut away
    • outside in cutting
    • climb cutting. use for finish
    • rough/finish cutting
    • instead of the tool
  • dimensions
    • 2.1D machine
      • multiple paths, each one going deeper
    • 2.5D machine
      • move in layers
    • 3D
      • move all in same time
    • 4D
    • 3 + 2D
    • 5D
  • make extra space in corner. called “dogboning”
  • onion-skinning
  • CAM software
    • CAM software, or Computer-Aided Manufacturing software, is a tool that uses computer technology to control machine tools in the manufacturing process. It translates designs from CAD (Computer-Aided Design) into instructions, typically in the form of G-code, that guide machines like CNC routers and milling machines to create parts accurately and efficiently.
    • mods
    • freecad
  • safety
    • more important that before
    • parts can come flying out
    • chips
    • set fires
    • parts can get hot
    • always wear safety glasses
    • no loose colothers
    • wear gloves
    • always be looking, listening and smelling
    • your hand is not a tool! you never reach in
    • dont do it when you are mad, tired, sleep-deprived. if you had a terrible day, dont make it worse.

Ferdi’s Addendum

  • unsere platten sind 18mm dick
  • 150cm auf 250cm
  • große böse maschine
  • we need:
    • exact times when to start safety training
    • when to do group assignment
    • slots when each of us can do the milling
    • an official text message in mattermost time:
  • test piece should be finished by thursday evening
    • we make a comb with dogbones, slightly bigger
  • assignment model by friday evening to be sent to ferdi to chekc it.
    • put it in the nextcloud folder
  • program: alchemy: the faster you go, the wigglier it goes. reactive to sound.
  • your board is never gonna be of constant thickness.
  • for the comb you go in 0.05 steps. from something thicker and soething thinner
    • upper bound: we need to measure it.
  • consider the weigth of the pieces.
  • do not assume that your wood is flat!
  • get inspired by the furniture.
  • opendesk
  • open source beehives
  • what else do you need for

group assignment - runout: milling bit will runout. due to spindle being not round. mill being slightly bent. several reasons for the tool not running concentric. - alignment: we shoud measure if it is running the righ tdistance in x and y. we would need a ruler that is 2m50 long. ikea paper rulers - tape measure - fixturing: machine has a vacuum table (document) - speeds: your cutting speed which is a compound that is a compound of rpm of your spindle, we gonna use the preset from fusion. we are not in a hurry. in the end its a rule that neil mentioned. if the machiene sounds like it is suffering, go slower - feed rate: moving speed of the mill. not rotational speed - toolpaths: - minimum speed just to get it rolling - we will use 6mm milling bit - in special cases you can use 4 mm milling bit - feeds: r - we take an indicator. when you push it in, it will measure the micrometers that oyu are pushing it.

  • if you mill a slot, your design looks like this. your wood is gonna perfectly fit in there. in reality oyou will have a round in the edges. there is alrays a radius of some mm in there. use dogbones. there are several types of dogbones. the ones where you just drill a whole iat the corner. its the ugliest one.
  • there is the one where you just go a bit furtgher and then go up.
  • freecad: construction lines. dimension it to be 45deg from corner. just draw circle where center is one the line and one point is on the corner. its just gonna eat away very little. this is the best-looking one and easy to make. in fusion there is a plugin.
  • in fusion you do not design the dogbones, you run a dressup feature.
  • there is software that is just made for simulating gcodes.
  • we do not meet tomorrow. the sooner you have something you can

literature: - in fusion generate gcode - check - make your designs in fusion - does not really make a big difference -

  • easiest way to do something big is to use dominos and do table stuff. click everything together.

  • we want to make something that has japanese style finger joints.

  • dont wanna use fasterners

  • we want to use cnc machine.

  • inspiration: burning man temple cnc

    • opendsk
    • atfab
    • copy something like this. as long as you model it yourself

  • using veneers

    • schachbrettmuster

  • look at pictures by escher

questions

  • can we also cut things larger than the cnc machine at the cnc guys place?
  • what about the different Ds?
  • when to use which tool?

Review

  • elle hahn from charlotte
    • made a cylinder with fancy side face.
  • ölöf from iceland
    • does art stuff
  • gillian
    • studies computer science
    • did some hut

Week 8: Electronics Production

  • Etching produces serious chemical waste
  • we do not do this in labs
  • we are milling
    • there are different types of endmills used for this.
    • endmills
  • tools
    • …
  • finish
    • …
  • you have to fixture your board proberly (otherwise it could bow…). otherwise your endmill might break
  • underlay
    • …
  • zeroing
    • let the probe “fall down” and mount it then
    • use a sheet of paper. if it does not move anymore, machine is zeroed
    • automated: using a probe and measuring the conduction between surface & endmill
  • milling
  • clean the board
    • your fat from the fingers will over time lead to bad board quality
  • mill on both sides.
    • make pins and holes so that board fits in..
  • alternative to milling: vinyl cutter
  • fancy stuff
    • vinyl cut copper -> epoxy over it
    • put traces on cardboard pressfit.
  • lasering
  • pcb materials
    • fr4: epoxy + glass. hard to machine. also produces poisonous stuff.
    • fr1 is what we used. not used commercially. does not go as high in temperature.
  • board houses
    • jlcpcb
    • pcbway
    • some of the components that are tricky to attach you can order a pcb house to solder it.
    • more layers possible in board houses.
  • problems with bread board
    • you need a complete set of partrs for them
    • pushing wires in a breadboard, ithere is no documentation + it does not elp you with creating the pcb
    • poor electrical properties
    • cables can flip out
    • creating pcb from a schematic instead is very
  • soldering
  • use lead-free …
  • making boards in the lab
    • generate toolpaths (we will get into that)
  • debugging
    • check your soldering
    • check your components orientation
    • go back to the dataseet. make sure pins
    • make sure connectors are oriented right
    • use volt meter to check voltages
    • then go to test equipment and look at signals of board.

question

  • what tools do we use for milling and why?
  • general rule
    • engraving bits
    • tapered bits
  • tasks:
    • holes
      • drills
      • milling bits are not usod for drilling.
    • polygons
    • cutting out board
    • slots (long hole)
      • end mill
    • traces (everything to remove copper)
      • copper or tapered bit
  • most important
    • base of machine is aligned to xy plane
    • if it is tenth of mm higher then somewhere else, you will break aend mill.
  • what is it about lead free stuff??
    • soldering tin
    • lead is in there sometimes
    • however, this is poisonous
  • if you have new machine
    • you take opferplatte you drill it flat.
    • screws need to be tightened
    • fixturing?
      • double sided tape: there are many different ones
      • carpet tape
      • however, these are difficult. this weaving inside makes wrinkles. thats too much.
      • dont use it
      • if you drop it to the ground, there is dreck in it
      • that will throw off your board. board will be off, mill will be broken
      • which tape do we use then?
        • simpler tape without weaven structure.
      • how to put on tape?
        • you leave the boarders of the pcb material
      • vacuum would also help. this is the way to go
  • pcb material
    • fr1: just paper with some oil
    • pcb materail could be bent.
    • you bend it straight
  • for pcbs we need to put our zero point on top. then we are going in minus direction for milling.

Review

  • sophia
    • problems with FR4:
      • kills your tool very quickly (does not deform)
      • short-glass fibers are just like asbestous. if you machining fr4 you need to make sure to treat it as hazardous waste.
  • ophelia
    • wants audio-reactive light
    • will have microphone
    • neils suggests
    • design of filters
    • have a filter bank. instead of computing hole spectrum one can just check if there is energy in one of the filter banks.
    • you do f(x) = α1xt + α2xt-1 + α3xt-3 thats a time delay band pass
    • lots of links how to pick coefficients.

Week 9: Input Devices

Lecture

  • connect via i2c
  • switches
  • magnetic field
    • applications: proximity of magnet and sensor
    • hall sensor
      • senses proximity of magnet
      • sensitive enough to measure earth magnetic field
    • vector magnetometer
      • has 3 magnetic field sensors. give you strength & orientation
      • basically you can build stuff like joy sticks with it where something moves relative to something else.
  • angle
    • es gibt chips die magnetische rotary encoder sind (digikey). verhältnismäßig neu. das ids dieser chip mit mehreren hall sensoren.
    • rotary encoder. viel zeug auf kleinem raum.w
    • trick ist dass man stattdessen einfach nen magnetic rotary encoder nimmt. der ist billiger.
    • als kit: motoduino
  • capacitive sensing
    • step response, ferdi explains
      • pt1 verhalten
      • ich gebe sprungsignal auf pt1 system
      • we would now want to know how long it takes for the pt1 glied to auflad? 4tau
      • also wir wollen das tau rausfinden
      • davon können wir dann auf andere größen schließen
      • wie können wir jattzt aber was messen was so viel kürzer ist was wir an samplerate haben?
      • trick: step response ist immer die gleiche. wir geben das ganze mehrmals auf das system und nehmen dann simpulsantwort mehrmals mit delay auf
      • dabei ist taktfrequenz höher als die sample rate. dadurch können wir das samplen um einen viel kleineren anteil der sample-periodendauer verzögern.
      • man kann natürlich auch einfch den maximalwert messen aber durch das pt1 zeug bin ich einfach genauer.
    • you have a single electrode. this acts as a capacitor (self-capacitance). its capacitance can be changed by changing its surroundings (dielectric), the location of the reference electrode (e.g. moving a finger) etc.
    • you then measure the capacitance in a very fast way by looking at the step response of the electrode (charging it and then listening to it discharging, doing this periodically)
      • check code for deteails
      • implemented this can be by measuring different step responses assuming they dont change or using the pios of an rp2040
    • if your electrodes are more farther away from the controller, have an attiny to take the measurement and send it to the controller digitally
    • alternative to that: have two electrodes: one receiving, one transmitting and you can sense things by changing the dielectric between them.
    • the signal from one electrode can be amplified.
    • applications
      • non-mechanical butten
      • force sensor
      • slider, rotary knobs
      • tilt sensor by putting liquid in a tube
      • liquid level as the liquid comes in.
      • distance between electrode: sense acceleration, rotation
      • have two static electrodes measure multiple times. change in moisture in air.
      • with increased frequency: measure on atom-scale, gather chemical, physical information.
    • touch pads (build yourself)
    • force sensor (adrian)
    • pressure, tilt, acceleration
    • questions:
      • what is the amplification at one electrode good for?
    • I checked the code from neil with the simplest configuration for capacitive measurement using the step response of a capacitor. https://academy.cba.mit.edu/classes/input_devices/step/RP2040/hello.steptime1.RP2040.py
    • this is how he measures capacity. he:
      • charges the electrode
      • then he lets it discharge
      • he somehow then counts the cycles needed until the electrode fully discharged (pin is zero).
    • this number varies if the capacity changes
    • he does not use any information on the exact curve of the step response or on how much the capacitor actually is charged, but just the number of cycles until full discharge.
    • one vs 2 electrode capacitive sensing
      • one: you need to be sure that the thing you want to sense capacity with actually is connected to gnd properly. i.e its changing the electric field properly
      • two: you can control that more fine-grained
  • temperature
    • thermistors, ntc, ptc
      • using measurement bridges. amplify voltage between those two points in bridge. this is advantageous to simple voltage: signal is relative to 0 and one can amplify it so that it covers the hole analog range of the controller. differential measurement.
    • infrared (blackbody radiation)
    • https://www.mouser.com/blog/ntc-thermistors-rtds-differ
  • light
    • photoresistor, photodiode, phototransistor
    • synchronous detection. blink with an led. take difference of then high-frequency component in photo signal.
    • light color
    • measuring rgb, orientation, signal strength -> gesture control motion
    • doppler radar. measures motion, is blind when stuff is still. but its not distance
    • pyroelectric. pretty much obsolete. doppler radar is sota
  • distance
    • laser time of flight
    • sonar modules. obsolete. laser time of flight better. however, difficult for laser with some surfaces. use sonar in that case. e.g. when measuring distance in water tank
  • clocks
    • rpc module
  • locations
    • gps modules
  • acceleration
  • sound
    • i2s: variant of i2c for audio
    • adafruit: microphone
  • force
    • straing gauge (messstreifen)
    • load cell
  • using camera:
    • invert, motion etection etc.
    • webrtc: video on the web.
  • vibration (piezo)
    • use as microphone, verstärker und so.

other links: - https://hackaday.com/2024/10/10/building-a-sound-camera-for-under-400/ - https://www.youtube.com/watch?v=DdbmTl0rhGw - https://www.fluke.com/en-us/products/industrial-imaging?srsltid=AfmBOorsNLllaUrIiiXxDo28F1MT6GTWG8uaaNo8iKMa_JhceDaKqy85

Ferdis Addendum

  • wir werden viele boards bauen
  • ferdi hat alle gebaut. das macht spaß sagt er
  • dc motor treiber
  • heizelement
  • empfehlung:
    • dev board for xiao bauen. damit kann man boards bauen wo nur der sensor dran ist.
  • wir müssen noch irgendwie rausfinden wie man die attiny s programmiert
  • ggf große kondensatoren verwenden. 4.7farad
  • group assignments: jeder macht group assignment für sich selbst
  • für alles was wir jetzt machen fräsen wir nen board.
  • https://www.bunniestudios.com/
  • input devices by daniele ingrassia
  • https://fabacademy.org/2020/labs/leon/students/adrian-torres/adrianino.html
  • hack with ir sensors:
    • cshiebetüren von innen öffnen: man nimmt wd40 (irgendwas mit treibgas) und sprüht das durch die schiebetür unter den pir sensor. der reagiert nämlich auf infrarot. also wärme.

Student Review

  • Ghadeer
  • jhasmin
    • neil: stencil
      • 2mm polycarbonate. you cannot laser that but mill it.
  • architect
    • achim menges
  • cs person from charlotte
    • neil suggestsamanda ghassaei
      • doing gear stuff
      • steampunky stuff
      • point to center of the universe
    • gravity battery

Week 10: Output Devices

Lecture & Ferdis Addendum

  • electrical safety
  • power
  • measuring power
    • imposing current, measuring voltage
    • imposing voltage, measuring current
    • measuring magnetic field around conductor.
  • leds
    • pwm
    • charlieplexing
    • you do not have to add current-limiting resistors if you have multiple leds in a row (look at data sheet).
  • MOSFETs
    • have Sourc (S), Gate (G), Drain (D)
    • N:
      • S is GND
      • for high-power and high-speed applications
    • P:
      • S high end of power
      • slower when switching
      • more effincient wrt power dssipation
      • higher ON resistance (resistance between source and drain when turned on), handle less current than N mosfets. use N mosfets for higher power
      • for low-power applications such as for battery-powered devices, logic scircuits and voltage regulators.
      • a bit more expensive than n channel mosfets since n mosfets can be easily mass-produced and they can be of smaller size.
    • resistor GND - gate, 10k: turn mosfet off as long as not told otherwise by code
    • resistor pin - gate: when mosfet is turned on, job of the resistor is to slow down transition from off to on. mosfet has capacitance behavior somehow.
  • displays
    • lcds: not recommended
    • oled: many tiny organic leds. each one cnotrollable as pixel.
    • tft: used for bigger displays
    • e-ink
  • motor
    • explaining video
    • ac power and ac motors are always fun but weird to control and change directions so maybe avoid them as a beginner
    • brushed dc motors
      • contain pads that have contact to brushes to have polarity to impose movement within magnetic field
      • a dc motor can also have a driver that converts a pwm signal into a position of the motor itself.
      • driver
        • speed of a motor can be controlled with pwm
        • you are not driving a motor directly, but you are using a mosfet
        • one can also use relays.
        • to protect the mosfet from currents induced by switching on/off the motor, insert a diode. some mosfets have a mosfet integrated
        • to switch the motor polarity, use a specific circuit. this is what the h-bridge does.
          • up left and low right: current goes left to right
          • up right and low left: current goes right to left
          • low left and low right: motor is stopped.
          • there is a part in the inventory that is an hbridge with some additional features around.
          • thermal pad underneath the h bridge
          • two extra capacitors
            • one bigger and one smaller in parallel
            • respond in different speeds.
            • smaller one: when there is spike in power line, couple that. smoothe thet
            • bigger one: when hbridge is asking for current, before the current comes in from the motor.
            • if not using this, sometimes this works, but sometimes not because because motor con be jittery and unreliable and controller could reset.
    • brushless (bldc, brushless dc)
    • stepper motor
      • 4 cables. connecting 2 other specific cables: make one step
      • the circuit doing this is called driver
      • driver
        • 1 signal to say in which direction to go, 1 signal to say “go”
        • microstepping: go more smoothly between the steps.
        • quiet steppers
        • polulu
        • darlington array
    • servomotor: any motor that is in a closed loop with a measurement device that measures where you are. Every motor can be “servo”.
      • turn motor into servo by adding an encoder.
      • one can also get the feedback by having some distance measurement thingy (for linear movements of the motor). you would use cerran for those, since cerran does not change with temperature.
      • there is a curve that defines how fast a motor turns over time. similar to adsr in audio synthesis.
    • linear motor: unfold the motor to have a line of magnets.
    • switching ac loads: hockey pocks. optically coupled.
  • speakers
    • calculating a soundwave
    • using pio of RP2040 for creating the PWM needed to get the generated sound.
  • solenoid
    • electromagnetic actuator
  • artificial muscles
  • shape-shifting fibers.
  • recommendations

Student Review

  • koharu played audio
  • akash from kochi made his own motor controller

Week 11: Networking

Lecture

  • reasons to network
    • different localities
    • parallelism
    • madoularity
    • interference might be an issue
  • wired communication
    • standards/concepts
      • uart
      • usart
      • sercom
      • pio
      • bit-bang
    • asynchronous serial
      • asynchronous: “we only have one data line, we need to agree on a data rate, we need to agree how wide our pulses are”
      • multi-drop serial
        • unique ids
        • bus
        • hard-coding address to each node
        • host tells then different nodes who should talk next.
        • in neils code: hard-coded node-id as a define statement.
        • adrian did a nice version of this with the 412
      • hop-count
        • not assigning addresses
        • assemble in daisychain
        • ws2812 work with this. they use hop-count.
        • node gets identity from number of hops of packet in network
      • broad-hop
        • lets main node talk fastly to any node but packages are hopped backwards.
        • also, any node can talk to (almost) any other node
      • those are all sync because you have to agree on the duration of a bit
    • synchronous
      • difference to async: clock signal in parallel
      • spi
        • SDI / POCI (peripheral out, controller in) / MISO (main in secondary out)
        • SDO / PICO (peripheral in, controller out) / MOSI (main out secondary in)
        • CS / SS (secondary select, you need one of those for each secondary)
        • SCK (clock)
        • example with talking with an sd card
          • both in python & c
          • neil does not recommend learning the fat filesystem handling part.
      • i2c
        • SCL (clock)
        • SDA (SDA)
        • lines can go in either direction
        • each line has a pull-up resistor, the node that wants to talk, pulls it down to talk
        • you need to have a fixed address
        • many sensors have addresses hard-coded
        • hints
          • having too many pull ups can cause problems, if every board has them
            • Advice:-, only do the pull up at the master / mother board , if using multiple nodes
            • Do I not need resistors on every node?
            • no, only a pair is generally enough. when using comercial breakouts it can even start causing problems, even though it only goes out of spec when having 2-4 pais of pull ups on the same bus. accounting for 5-10k resistors
            • https://fabacademy.org/2020/labs/leon/students/adrian-torres/week14.html#hello_i2c
        • if anyone has problems with i2c I have some documentation on debugging it. https://fabacademy.org/2022/labs/fct/students/ricardo-marques/assignments/week11-2/
      • i3c
        • there is a standard evolving i3c
    • asynchronous unclocked
      • atp: asynchronous token protocol
      • designed to work without clockes
      • two lines in each direction
        • bit (low, high, information)
        • token (is it valid)
        • tb: 00: nothings there
        • 01: occopied, not saying value
      • way to exchange value:
        • sending side says “i have a token” & puts up data
        • receiving side says “i am occupied” -> “i have accepted your data”
        • sending side 00 “you have taken my data”
        • receiving side “i am empty”, i have accepted it back from you"
    • long cables
      • when long cable, lot of capacitance & inductance
      • it can take a long time to charge & if the signal travels down, you can get reflections
      • at high data rates, much more thought goes into how you drive them & how you terminate them.
      • it is not an issue with the sizes we are talking about
    • usb
      • tinyusb
      • arduino: present as midi
      • using the usb stack you can present a device as specific peripheral
    • ethernet, can, lin, modbus
  • radio
    • ism (industrial, s…, medical)
    • where to talk, in which bands
    • depending on which one to use they can be quite cluttered
    • as you go down in frequency, the data rate goes down, the distance you go goes up
    • less sensitive to things like walls, you can go inside, around buildings
    • as you go up in frequency, the range goes down, gets reflected by walls, data rate goes up
    • parts of a radio
      • oscillatior: makes radio signal
      • mixer: combines with message you want to send
      • pa: power amplifier (sending)
      • lna: low noise amplifier (receiving)
      • if: intermediate frequency that crosses the signal
      • i/q: how you modulate it
      • demodulation: seperate message from radio carrier
      • baseband: …
      • filters: …
    • antennas
      • antenna theory: analysis and design (antenna bible)
      • antennas are tuned. if you look at frequency and the amplitude, typically antennas have a center frequency (somehow they are like a filter).
      • different types of antennas: radial, more energy in one direction
      • impedance matching
        • high-frequency signal over long wire gets reflected (somewhere inside the circuit before the antenna)
        • to circumvent, you need to do something called impedance matching. we wont cover that
        • check the physics of information technology by neil gershenfield
    • single-chip radios
      • we are gonna toalk about single-chip radios. they contain everything neil talked about.
      • once upon a time, we used to use those from scratch and built everything else
      • now, one gets more complex chips having radio plus protocol
      • esp32-c3 is our favourite
    • esp23
      • connector for antenna, has radio on board
      • has wifi + bluetooth
      • implementing web server
        • over wifi
        • over bluetooth
      • implementing an interface for wire over bluetooth
    • esp01
      • even cheaper radio module for radio
    • nRF24L01 + the other one, different modules, different frequencies
      • sdr
    • some modules that communicate on non-crowded bands
    • bu01
      • rf positioning. track sources of rf
    • gnuradio
      • amplifier out and in, maybe one mixer
      • rest of radio is implemented in software
    • openwrt
    • 4g
    • lora vs lorawan
      • lora specifies nothing
      • lorawan specifies protocol stack
    • meshtastic
      • farm where you have multiple sensors & pumps & you want to connect all of them.
      • can connect stuff with lora but meshtastic also ok
  • networking
  • funny stuff

Questions

@Neil Let me ask a question that I think is related to networking and communications. Tarlogic has announced that 29 vendor-specific, undisclosed, hidden commands have been found in the ESP32, which is well known for its wireless communication capabilities, and can be hacked using HCI commands. We understand that there is a trade-off between convenience and security, but we would like to eventually develop products that communicate wirelessly, and security is a very important issue for our business. (How much of the responsibility lies with the manufacturer remains to be seen…🤔). ESP is very useful ,so, it is very sad that we cannot use it, but shouldn’t we use it? I would be very grateful if you could tell us what you think at this point.

Ferdi’s Addendum

  • serial is already enough
  • wifi is getting easier
  • we have unikat wifi
  • similar to freifunk
    • guifi.net
    • fonera
  • trick for doing freifunk
    • check highways. they are build together with fiberglass cables
    • check public services next to these highways and ask them to provide uplink
  • einfachste variante: serielle kommunikation
  • spi
    • chip select pin (one for each node)
  • i2c
    • dest address is sent in signal

Student Review

Week 12: Mechanical Design, Machine Design

Lecture: Mechanical Design

  • a machine is
    • mechanism: things that move
    • actuation: things that make it move
    • automation: control of whats making it move
    • application
  • vendors
    • mcmaster-carr: not necessarily for buying it, but well-documented
      • have any mechanical component. you get all different norms.
      • in europe there are different shops for everythign
    • stock drive products
    • amazon industrial
    • misumi
    • motedis.es (cheap, really cheap) (they have no service)
  • principles
    • stress, strain curve
      • stress: press, what i du
      • strain: pain, what i feel
      • when you push the material far enough, there is a hysteresis
      • eventually you get to a stress lmiit where material fails
      • stress point where material fails is “strength”
      • area under curve is “hardness/toughness”
    • backlash
      • how much a nut wobbles on a screw
      • also, if you change direction, you will get an error, so you travel back and forth, you will not end up at the same point
      • if you want to be really precise, you start travelling from the same side
      • trapezoidal screws: a bit better than normal screws with this. but not perfect
      • what you actually would use are ball bearings
      • also, you can screw two nuts against each other, that would decrease the backlash, but then they dont move, they need to be a bit apart from each other. so you put a spring in between. but you dont want to be able to compress the spring which would introduce backlash again, so you need a spring that is stiff in just the right way.
    • error
      • error is a stackup of the errors in the whole force loop
      • to design the machine to make the tolerance tight, we need to understand the errors in tho whole force loop. we want to minimize the force loop to minimize the error stackup.
    • kinematic coupling
      • if you take one slot and one ball, its free to move on that line. if you make three of those, each of those is constrained along a line, total structure can only go in one position.
    • maxwell criterion
      • a structure has constraints and degrees of freedom
      • as you build a machine, you need to keep track of what are the constraints
    • accuracy vs precision
      • accurate: centered around the wanted point
      • precise: low deviation
  • more materials
    • high-density polyethylene
    • metal
    • rubber, foams: damp energy
    • carbon fiber: hazardous to machine, not recommended
    • garolyte: friendly to machine, nice machinery
    • wood: will swell as temperature changes. not recommended
    • cement: very stiff, much mass, can be casted
    • ceramics: for the parts that need to be very hard. there are ceramic precursers you can mold, fire, -> boom, ceramics
  • adhesives
    • use to glue things together.
    • in general, we stay away from them, because it is hard to undo them.
    • we want to be able to disassemble the machine
  • fasteners
    • nut:
      • used for tightening
      • if machine tightens, it vibrates, loosens the nut
      • therfore, use lock washers
      • washers then used for not deforming the material
      • lock nuts are somehow self-tightening
    • heat-set inserts
      • for the use with 3d printers
    • rivets
  • framing
    • extrusions, t-slot parts. very nice. metal or plastic
    • self-aligning joints (like snap-fit, fancy)
  • drive
  • guides
    • shafts: hardened rods you can slide along
    • guide rails: go on a shaft
    • slides: lower cost, if you dont need precision, you just need to move something.
  • coupling the motor
    • when there is much force on the motor, it is a problem if there is any misalignment between motor and the part where the motor goes in
    • you take a slightly flexible, but mostly stiff thing and attach it between the motor and the part where the motor goes in.
  • bearings:
    • needed because if you move things, there would be friction
    • ball bearings (rotary force)
    • thrust bearing: if something heavy lies horizontally and rotates
    • linear bearing (moving along a straight line), on a rail
    • sleeve bearings: if forces are not large, they are cheap and easy to use
    • pillow block: slide surfaces together, not used for large forces
    • skateboard bearings
      • sealed ones, do not need to be re-lubricated
      • good design principle: a bit of axial load on the bearing, so the bearing does not rattle around
      • 608 ball bearing bc its the cheapest
    • v-rail to route sheet metal or filament.
  • cables
  • mechanisms
    • flexures: smooth motions, for limited travel
    • series elastics: rather than specifying position, one specifies force (using springs) which leads to more smooth trajectories
    • linkages: turning all kind of motions into other motions
    • wippletree
    • pentograph: big motion control small motion
    • deltabot: 3 linear motions
    • hexapod
    • corexy: minimize the mass to be moved
  • cool stuff
    • hangprinter
    • chuck hoberman. massive stadium-size mechanisms
    • strandbeests. complete wind-powered things
    • modular machines, object oriented machines thesis

Lecture: Machine Design

Ferdi’s Addendum

  • most important
    • if you cant make it precise enough, make it adjustable
      • wedging stuff into something is a nice way to make stuff adjustable
    • round/rotary stuff is cheaper than straight stuff
  • literature
  • forward vs backward kinematics
  • how to make things straight?
    • interferometry
    • take two things, put ink, rub them together. then you see where thing is not flat, you can sand it off.
    • what if your two pieces are actually crooked but in a way that their touching everywhere. you take three parts to circumvent this.
  • guides guides
    • also have balls inside. you take a plastic thing when taking it off
    • ball bearings
    • one can make a cnc machine only with 3 rotary axes
      • it is cheaper to do that. since you only need a lathe for making the stuff
    • shopbot
      • somehow that is not a scraped bed
      • but there is also not hiwing bearing
      • it is cheap because of using the v-bearings
    • for bending sheet metal, you need a shet metal press
    • coupler
      • if you try to align the motor, you will never manage to get this straight.
    • linear …
      • v-slot guides
        • problems…
      • screws
      • ball screws are more expensive, but yet another alternative
      • backlash
      • problem with bearings
        • wenn du ne führung hast möchtest du sie irgendwie in der mitte stützen. damit sich das nicht verbiegt. deshalb nimmst du führungen die
        • wir wollen guieded rod. linear guide rod welded onto schienen. you can screw the schienen onto your machine.
      • you can make a linear guide by bending sheet metal 45 degrees
      • problem: if you buy sheet metal, the cut is probably not nice. you can also buiy it laser cut
      • it is hard to produce long linear gears
  • gears
    • cog vs pinion
  • belts
  • v profiles
  • if you use ball bearings, always us ethem in pairs. if you just have one of them, they would wobble. you put two bearings next to each other so they are spread.o