stepper motors
I started looking into how tiny and cheap steppers can get, since micro servos are in the $2-3 range, and holy lady hexapods they can get tiny.
Instead, a search for “nano stepper motor” reveals this:
More info here, including the fact that this stepper can be driven directly by an Arduino. On amazon, these cost ~$2-3 each as well. (search for “stepper motor gauge”).
I just order 6 for $16.50 to have some hand to play with (randomly ordering the micro-servos a while back turned out well); we’ll see how this goes. So, upcoming tiny stepper gantry?
Some more reasonable 15 cm ones cost ~$15 (vs the price on mcmaster…)
flying things
from the facelols, charles seyz
i think these days about $150
for the average kramnik kopter
frame: $20-30 from HK. motors: $10each. esc: $15 each. kk2 board: $20
i guess add in radio and gaudy lighting too so $180-200
so
if you are fine with small
less than $100 is definitely possible
tinycopter runs like $7-8 motors and $8ish ESCs
the frame was made of a few 3d printed doobobs and carbon fiber
you can get CF sticks cheaply and i’m sure the 3dp stuff can be replaced with lazzered parts
this is why i am considering it:
i think flying things are an example of neat engineering
but that’s [$180] too expensive to justify
if it were in the $80-100 range
for a reasonably robust multicopter
that could be reliably produced (not made from chopsticks)
current commercial options, which are super-slick and $150
Uweh. That is SO AWESOME. Actually now I am not so sure there is much point trying to drive the cost down to $80 or so with reusable parts. Then again, if the kits are derpy enough, they should encourage people taking the course to go forth and build better versions.
In theory, tricopters would cut down on costs even more (take out a motor, propeller, and ESC). But something about they are more mechanically complex (extra component, servo rudder)? I might be confused here.
start-lolling
what is this all about?
in my pursuit of excessive feedback / encouragement wherever I can find it, I input to 100k coaches corner (sort of questionable since I have no intention of entering the 100k ~_~) yet another description of what I intend to work on:
Khan academy / Udacity with hands-on mechanical engineering projects, fully kitted so no fabrication resources are required, aimed at high school+university level.
the current plan is to have three projects, a micro-robot arm, a nano-quadcopter, and a nano-stepper gantry. (Maybe some swarm robots? What other buzzword robots are there? Anyway). Realistically I would be happy just running with the first one, since the timeline is so short (six months until I run out of health insurance). But it’s fun to think about the other two/three/infinity.
idk why I feel so awkward about pursuing a startup full force except that my group of friends seems to have a reactionary “too cool for startups” attitude .__.
misc. info health insurance after graduating
I’m in this awkward position where I cannot get coverage under my parents. Given my recent spate of issues after a lifetime of not needing to go to the hospital, insurance is a good idea (plus, it’s mandated in MA). Therefore: http://medweb.mit.edu/healthplans/student/after_graduation.html
“Your MIT Health Plan coverage continues through August 31”
Ouch, so the FSA (no strings attached MIT accelerator) ends on the 21st with a Demo Day on September 7th. By which point in time it’s most likely I’ll have decided this won’t get to the scale I need to sustain myself and look for a full-time job, but just in case:
“you must apply before August 1 for your new coverage to be effective starting September 1.”
Uhm, what, I have to call to get a quote. Meh. Looks like in the range of $200 a month as of three years ago.
(http://www.city-data.com/forum/massachusetts/541525-how-much-do-you-pay-health-3.html).
There’s a video of it in its final state, with its multitude of issues. *sigh* one day I will actually finish a project. Only the first and last 5 seconds or so are interesting. Cost: ~$6 for the two microservos (!! so cheap), plastic is free, then the board+microcontroller battery is $25+$15+free (probably $10?).
After building hexa-rideablepod, I have definitely been more inclined to daydream about small or fold-able or compact project.
I should update my project todo list.
Anyway, I started at ~8pm on Saturday and finished ~3:30 pm on Sunday (and yes, I did sleep a bit, as well as watch an anime movie (Summer Wars) …
I was a bit confused by the definitions of the variables, since I haven’t done kinematics in a while. In the forward kinematics part it is essentially saying:
measuring the servo spline outer diameter in order to create lasercut female splines on my parts instead of using the proprietary servo horns. I started around this time. I swear I spent like 30 minutes trying to figure out how many divots it has (21) before just trial-erroring it, lol.
Well, crap. I hesitate — do I want to try to get something done and present a project or not? I eventually decide (and with some support from the awesome Jessica Artiles) that I may as well get more feedback on my ideas. What is there to lose?
Thus, I emergency hot-glued some potentiometers onto pieces of plastic and used that as my control ( a simple mapping of potentiometer values to servo values is all that’s needed) instead of writing IK code. This arm controller design was inspired by http://www.maxjusticz.com/a-miniature-robotic-arm-controller/.
img src my design inspiration, except mine was jankier and used more hot glue
near the end of the designathon
I didn’t even have time to map things correctly, because I thought the presentations began at 5pm but actually they began at 3pm.
The lasercutter files looked like so:
It’s hard to see the cuts. But the pots have flats on their shafts, so the pot arms have semicircular holes that are tightly fit onto the pot shaft to couple rotationally. And for a minimalistic design, the robot arms have servo splines cut into them so they mate directly to the servo.
I had the most issues trying to make a press-fit bracket for the servo so that I could couple it to a base. The sides of the servo weren’t particularly flat so the rectangular brackets always broke on installation; I ended up with a C-shaped bracked design.
a frontal image
Also, the servos are amazingly torque-ful. I thought the base would be enough to hold it down but I ended up adding tape so that the servo arm wouldn’t swing itself around.
Also to fix, I actually need to build a platform so that the base is heavy enough that the servos don’t push it around and high enough that at zero degrees the width of the servo arm doesn’t cause it to hit the ground.
I also actually did calculations for the servo, or rather used a calculator online, to verify the servos would handle the sharpie weight. Not that I had different servos or anything. (screenshot below)
Oh, another issue I ran into, the servo.write() arduino library uses modulation from 544us to 2400us, while the microservos used 500-2400 us, which gave me this issue where the servos wouldn’t go all the way down to zero degrees when I used myservo.write(0). I took a quick look at “arduino-1.0librariesServo” and found out thatyou can specify these min/max values when you initialize the servo, e.g.
attach(pin ) - Attaches a servo motor to an i/o pin. attach(pin, min, max ) - Attaches to a pin setting min and max values in microseconds
There was some other funky issue with trying to read a sensor while the servo was drawing power. Turns out I just need more delay in my loop.
Can’t thinkof anything else for now. Material Costs
ebay $11.88
“4x SG90s 9G CYS micro servo motor RC Robot Helicopter Airplane Car Boat + Horns”
Current Status: I lost the code, and I broke some of the lasercut pieces, (the usb port for programming the arduino also seems to create a lot of sensor noise and the servo arm kind of did crazy robot arm thing and killed itself) so right now I re-lasercut pieces and am re-writing the code. Should be up within a week.
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Follows is a live blog of me working on drawbot:
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ebay $11.88
“4x SG90s 9G CYS micro servo motor RC Robot Helicopter Airplane Car Boat + Horns”
== okay, assume some weights google: density of acrylic 1.18 g/cm³ thanks google
okay let’s make up some dimensions for a link length 4x16x3 = 192 cm^3 * 1.18 g/cm^3 = 226.56 thanks dot-gridded metric notebook and google
hrm, so about 1/5th of a kg. Wait what? that seems wrong.
oh units -> 0.3cm thick, so = 22.7 grams.
(from actual measurements: 15g for a 3*50*76 mm chunk, or 1.32 g/cm^3
okay now for pre-built calculator! 😛
okay not operating near stall torque, that is good
(conversion N m to kg cm is about x10, if you let gravity ~10 m/s/s) == 8:30 okay, screw this, I am going to CAD some stuff later: end up not CADing anything == 3:18 One anime later, and back to staring at robots. i start watching youtube stanford lectures but am too sleepy http://www.cs.unc.edu/~jeffi/c-space/robot.xhtml mmm canvas, 2010 2d robot arm simulator
Exciting, when I am commanding a servo, it pollutes the analogRead. Well then.
Oh, I just needed to increase the delay (was using 1). Hmm. I’m not even writing to the servos. I wonder why initializing the servo means the serial loop can’t run fast enough.
Ugh, the Founders’ Skill Accelerator application is in this dumb form format, where you have to fill out required questions on each page before seeing the rest of the application. I put in dummy answers and then compiled all the questions the application asks as of now.
Teams should commit to work in the FSA office space for the duration of the summer (June 1-August 31), and present at the Demo Day on September 7. Page 1 Deadline: Friday, April 5, 2013 at 5pm EST Bio (2-3 students) for each of us
How long have you known each other, and what have you worked on in the past? (Include past work done on this project, if applicable.) Will the team member work in the FSA space Room E40-160 in Cambridge, Mass. for the duration of the summer (June 1 – Aug 31)?
Page 2 Your Project We call each team’s work a “project” to emphasize the educational nature of the accelerator.
What problem are you trying to solve through your project?
Tweet us your elevator pitch — give us your elevator pitch in 140 characters or less.
Page 3
Proposed Milestones (aka how your team earns up to $20K!) What do you want to achieve this summer? We will work with you to create rigorous yet achievable milestones, but we’d first like to hear from you. Where do you want your team to be by mid-September regarding customers, product, team, and finances? (list 2-5) For more explanation about milestones, including examples, please go to http://entrepreneurship.mit.edu/fsa
Proposed Customer Milestones (list 2-5 for each)
customers
product
team
finances
http://entrepreneurship.mit.edu/fsa/milestones Page 4 Additional Questions What inspired your team to get together and work on this project?
Who do you view as your competitors, and how do you differ from them?
Who is your target customer? (Hint: “Everyone” is not the right answer.)
Have you received any funding (including angels, family/friends, personal dollars invested, etc.)? Do you have any customers? (These two questions help us gauge your starting point, so don’t worry, there is no “wrong answer.”)
We will have a lot of applications for this program, so choosing our final teams will be tough. Why do you think you should rise to the top? What sets you apart from other teams?
== Questions I need to ask: Can I work out of IDC space instead (the MIT-SUTD international design center is a co-sponsor of this) of the E15 space? Incorporation of media (e.g. video) into application? Alternative resources (because way to hang by a thread until May 1st)?
Key dates:
Due Friday, April 5 at 5pm. (week after spring break)
Notified by May 1st.
Work in space for duration of the summer (June 1-August 31), and present at the Demo Day on September 7.
Notes:
A select number of teams (in 2012, there were 26) will be interviewed in person during the week of April 22. Of the teams interviewed, we expect to select 8 teams for FSA 2013, but the FSA organizing team has full discretion over the number of teams selected.
So… odds are not great. Stipends are nice. Stipends will feed me. Maybe I should look into trying to get no-strings attached grants from places?
