Category Archives: Hexapods

hi 2016 (2 servo drawing robot arm, tripod gait 12 servo hexapod, visit to NASA, quadcopter tuning, etc.)

hm, haven’t updated in a while.

i built a lot of robots with parents over the winter break. i built a robot arm and refreshed on inverse kinematics; more specifically, make sure your servos are rotating as you expect: IK goes counterclockwise since angles increase that way, but your servos may increasing in a clockwise direction… a simple map(theta, 0, 180, 180, 0) will fix your problem if you catch it.


processing takes in x,y coordinates drawn on the screen and spits them out to arduino over serial, which does the inverse kinematics and spits out the theta values to the servo

or for the one where it draws what you draw on the screen,

also tried to face.

it does not face well, in part i have derpy three year old code


this processing code takes a lot of processing libraries. thresholds image, performs canny edge detection, then a walking algorithm (look at each black pixel by scanning image in x and y, see if neighbors are black as well, then walk along that pixel) to turn the edges into vectors. then output to robot, but robot is limited in resolution (arduino servo library) and cheap hobby servo overshoot.

below you can see preview in python.  (basic code, I basically copied the output from processing into a text file and  added some python code to that to plot the values)

is to check image is within the working envelope of the arm. IK is fixed with arm “up”.



problem of walking algorithm: adds a box around the image. irritating. need to rewrite code. looking into open cv.

i also rehashed my hexapod project with 12 servos and popsicle sticks


basically this

but modified to work with the servo configuration on the rectangular robot, and added code to allow you to step through the gait with “j” and “k”:

need to implement the other gaits; also, this moves so smoothly, envious, but they have lasercutter :3

worked on quad, now stuck at calibration stage 😡 because i have not built quad before, i could not push through this in a day or two unlike the drawing arm and hexapod.



made from a sad clothes drying rack we took apart





we couldn’t find the original cable for the transmitter, so we connected the ports up with a FTDI -> USB cable as per


used and calibrated my servos to zero… took a while to realize it *can* and *should* read the current values, guess my wires were loose, but the values because a lot easier to input. used the kk2 screen to fix some controls that were reversed from what the kk2 expected (left = left and not right, etc.). zeroed all the values on the kk2. turns out (minus the flipping controls) I could zero just as well on using the trim knobs on the controller itself.

went to visit NASA space museum in houston. they had little robot that made and served you froyo. adorable.


also, some regal looking hexapods in the actual NASA workplace.



at MITERS I got a robot arm working with lots of help from MITERS / London Hackerspace / john from BUILDS. For robot arm competition.

i’m now robot art-ing. here is using Fengrave on a black and white image with appropriate offsets to produce gcode (well, limited to G0 and G1 commands)



face code still derp. (streaks are because i wrote gcode translator, and it goes to x,y,z position instead of x,y and then z). too many x,y points. draws slowly.


michael made crayon extruder (=metal tube + power resistor) and also pen mount. crayons = hard to control flow rate. started making square, then pooped out a lot of melted crayon. alas.


learned a lot of patience dealing with old manuals, 20 year old operating systems / controllers. main issue turned out to be a dumb calibration assumption (robot had arrows; should have ignored them and used indentations instead). gcode -> V+

also, i learned about oscilloscope rs232 decoder! had to invert to get it working properly (zeros are high in rs232?). scope ground, tx line. bam, now you can check whether you are actually transmitting all the carriage return and line feeds you need…


currently: reading up on image processing. openCV.

terse update. more details available if questions exist.

many thanks to my parents for being excited and not jaded

boston winter 2015: it snowed a lot.

snopocalypse? snowmaggedon?

Jan 27 2015 snow
Jan 27 2015 snow

Here in Boston, it didn’t snow at all the last few months, and then suddenly it snowed a lot (90” over the last 30 days).

Here are some sweet graphs from Samuel Lillo
Source: Samuel Lillo
Source: Samuel Lillo

On the plus side, I’ve now met my neighbors (since they’re outside shoveling for hours). At this point, we just throw the snow up as high as we can onto piles of snow. There’s nowhere to shovel to snow to…

when the snowbanks are higher than you, where do you shovel snow to?

I’ve also made new friends and spent quality time with my roommates. We all co-work, since everyone is working from home because our city cannot handle the snow. *


* I come from Georgia. My Boston friends were laughing last year about Atlanta shutting down due to a few inches of snow. WHO’S LAUGHING NOW HUH? 😛 My Alaskan friends tell me our Boston snowfall is normal for them, but their cities are built to handle it.

Here is a large icicle.


It later fell and broke the railing/steps on our side-access porch. o__o Apparently, falling icicles do kill people. I’m glad no one died from our icicles.

Here are some more pictures of my poor bike. <3 bike, I will spend $$ and give you a professional tune-up after winter is over.


Biking in boston is a struggle right now. The major streets are passable, but all the bike racks are very buried. For instance, at wework south station, they admonished me for locking to the railing I didn’t need to step in chest-high snow to reach. To add insult to injury, when I got out of work the railing was blocked anyway by trash bags. :/

bike at work on top of bike racks
bike at work on top of bike racks that are buried in snow

Here is my bike after the valentine’s weekend snowstorm. i left it overnight on top of a snowpile in order to lock it to something. When I left, I had a “where did I lock up?” moment. It was well-camouflaged.


here are some pictures from my friends

mt. albany street snow farm

mt. mit, mt. simmons, mt. albany
back when it was “just” 3.5 stories tall.

mt. mit, mt. simmons, mt. albany, mt. cambridge, who knows

view from the top
view from the top


There were some silly snow vehicles: fansled aka meloncraft, ebike-ski, and scooter-ski

For technical details / build reports, see

around the web

our mayor is flummoxed

Walsh: “I don’t know what to say to anybody anymore. Hopefully it will stop eventually”

Turns out the National Weather Service meteorologists are humans and not computers





(i wonder why they have ellipses… AND ALL CAPS… is it for maritime radio, which I’ve now spent hours listening to … for their text-to-speech synthesizer… trivia, maritime radio weather reports have three voices since 2002… here are some voice samples via NOAA “Voice Improvement Processor” … listening to it brings up salty memories for me)

weather is happening

He just appeared on WMBR too. at 24 mins in. If you want your daily dose of Angry Boston Weather Preacher Dude.

train through snow

everyday i’m shovelling

MBTA quick reference map


Note: I dug out some of this from

highway signs with a boston accent

Source: 5wcvb ABS news?
Source: 5wcvb ABS news?

build a snow igloo, then rent it out on airbnb?

Screenshot from 2015-02-17 00:54:51

PSA: Be careful. Turns out collapsing snow caves can kill you by asphyxiation. This happens when snow plows don’t realize it’s a snow cave instead of a snow bank and dump tons of snow on top of your cave. Then you die. So make sure to stick a flag with a picture of a human on top of your snow cave, and don’t make it on the side of the street.

weather forecasts

predicting the future is hard. here are some good websites to help you (great UI, graphs temperature forecast for you and you can hover over it for instance to check out the likelihood it will be raining at 1pm on Tuesday)

Add Media (links to the national weather forecast broadcasts)

Screenshot from 2015-02-16 23:37:42 (comes with webcams! very clean and detailed) (if you like a dose of snarky with your forecast) SNOBLOBS

here is a narwhal on a narwhal

to end on a happier note, here is some cuteness for you

narwhals on narwhals
narwhals on narwhals

I finished a hexapod instructables, get featured, and then mope some more

I finished my second instructables ever! This one was a lot more “successful” than my first one — it was featured on the front page for a day or two. 😀 yay!

This is the instructables for my 18 degree of freedom (18 servo) hexapod:

It probably took slightly less time than my 7 minute video on the design process (which took at least 2 or 3 full days) yet garnered about 10x the views. The little star in the upper right hand corner stands for featured.

All that it means is that your instructables gets put on the front page for a little while. At least it did much better than CNC nyancake. Apparently nyancat is a thing of the past for everyone except me XD;

day 1
day 2

It was featured within hours of posting, crazy moderators.

instructables published jun 24th

It is gratifying to see that at least some of the thousands of people who visited that instructables clicked through to my took-ages-to-make design process of a hexapod video. See spike in traffic at the end of June.
I still don’t know the secret to getting comments though. I want to interact with people virtually! At least for now.
As usual — then I mope about how I focus too much on these sorts of stats instead of going out and “enjoying what I do” or whatever.
But yea, all in all. Four years ago I never would have imagined being on hackaday and having a featured instructables. These were all things I saw the peers I looked up to do, not myself. Yet I find myself qualifying these accomplishments — it was just for a project I basically copied off the internet, it is just for a really derpy hexapod I never really finished, etc. I have an awesome friend who was published in science as an undergraduate, yet she always qualifies her publication, and it’s obvious that she’s missing how amazing this whole thing is. Maybe I am doing that?
Lack of self-confidence is unattractive and can make other people difficult to work / high maintenance with, yet I can’t get rid of this in myself. Grr! At least there is hope for me. I can reasonable list three things every day that I am proud of myself for, unlike some friends of mine. x___x must spread positive energy

Well, that’s life in the first world. I am in an amazing spot for myself currently — working on my own startup with two very good friends who are still my friends so far, assisting with a go-kart class for pay, no financial issues for at least a few months — yet I still feel not-legit, like I haven’t really built anything really cool or robust. I’m not sure what it’ll take, since I certainly won’t catch up anytime soon to people I look up to in the areas they specialize in.

I guess that is just something I will have to get used to. Or I could finish kiwikart