All posts by nouyang

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Nyantart, “a strawberry poptart laser-engraved with nyan cat”

There’s something about watching the media lab lasercutter etch nyancat onto a strawberry poptart that is soul-deep satisfying. Surely now the quality of my education is irrefutably worth my tuition…

meta-nyan! not yet recursive…

The most difficult part of this turns out to be not eating the poptarts long enough to make it from the grocery store to the lasercutter. I’ve wanted to do this for weeks, ever since I saw the Louisville hackerspace posting: http://www.lvl1.org/2011/07/15/new-laser-cutter/, but never made it to the lasercutter until last night. (and I’d never even eaten poptarts before the first time I bought poptarts with the intention of lasercutting them, hah).

that’s the original inspiration on the right

So, first things first, go to google images and find an image to trace (I used: http://thelemurblog.com/gallery/Nyan%20Cat.png). I tried to do my grid + draw lines method that I used with solidworks, now in GIMP, but ended up simply using select-by-color + bucket-fill-entire-selection.

this is the exact picture I used, if you want to laser-etch one of your own.

Then, play around with the lasercutter settings.

This is what I found to work (sorry for the terrible formatting):

MATERIAL:  LENS:  THICKNESS:  PPI:  POWER (%):  SPEED (%):  EFFECT (cut/etch)
Poptart            2    n/a        500    40%        80%        Light raster (will cut through sugar but not burn poptart)
Poptart            2    n/a        500    40%        50%        Medium raster (will cut through sugar and lightly singe poptart)
Poptart            2    n/a        500    76%        50%        Strong raster (will cut through sugar and darkly singe poptart)
on the universal laser x2-600 (co2, 100w).

I stuck it in Coreldraw on a 32×18” bed to make sure it was placed correctly, then thanks to the Windows printer drivers, I simply hit Ctrl-P, set the settings, and printed it.

laser, do my bidding!
a few minutes and done~

Verdict: Still pretty tasty. The burnt ones tastes burnt, but both don’t taste as bad as the lasercut sugar cookies.

light and strong rasters, side-by-side

reddit?
Haha, I put this up on facebook and not half an hour later it pops up on reddit:
http://www.reddit.com/r/pics/comments/lyktg/just_a_strawberry_poptart_laserengraved_with_nyan/

I wonder how it made its way there o.o?? I only posted it on facebook (this blog post was after the fact), so it’s a little creepy.

FAQ
People wondering how they can make one of their own–
http://fslaser.com/40w-deluxe-hobby-laser-engraver-and-cutter
$2.5 to 3k 40W CO2 laser may be your best bet for cheap. It comes with caveats, though, see: http://hackaday.com/2011/04/14/buying-a-laser-cutter-from-china/ and other reviews online.
Probably a better idea to instead look at the list of hacker/makerspaces and contact your nearest one to see if they have a lasercutter you can use. http://hackerspaces.org/wiki/List_of_Hacker_Spaces
Alternatively, cut a stencil out of aluminum foil and blowtorch-singe or stovetop-pan-singe the appropriate parts. Although this tends to make a melty mess and I’m not sure how you would cut a stencil for a shape like this — I guess connect some areas with thin bridges like they do for stenciled letters.
Although probably not recommended depending on what else was cut in the lasercutter, the resultant poptart is safe to eat — it’s the equivalent of a poptart which was super-toasted in some areas (all the laser is doing is dumping heat into some parts of the poptart, it’s not dumping radiation or anything).
In fact, I stuck it in my hall’s free-food table and both nyantarts were gone in an hour. 🙂

Oh, and more pictures here:
https://picasaweb.google.com/113942194695013581888/Nyantart#

Other nyancat shenanigans in the last month of two: (e.g. cutting it out of aluminum, making a mold for it): http://www.orangenarwhals.com/search/label/nyancat

Todo
Next up: embed one of these suckers into the poptart and have it sing too!

http://www.instructables.com/id/Musical-Greeting-Card/

Then, after that, make a pressfit cookie nyancar. 🙂 Like this, but with gingerbread (this is done in masonite) and with a nyancat center:


http://fab.cba.mit.edu/classes/MIT/863.09/people/mellis/pressfit/index.html

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Package Arrival Email Automation, google apps script

The packages for MITERS makerships are being routed through me (to force people to go to MITERS, heh). I wrote a quick and dirty script to automate notifying people by email when the packages arrive at MITERS. My first try at google apps scripting.
Google’s documentation is excellent: http://code.google.com/googleapps/appsscript/service_spreadsheet.html
The code is like so:

Which corresponds to a spreadsheet is set up like so.

So, the full steps:
You start out with the raw spreadsheet. Then, to add a script to it, got to Tools > Script Editor… which will take you to a blank version of the following. To check your script for errors, you hit the play button here.

Now, go to Tools > Script Manager > Run to run your script and create the custom menu (which is just for convenience for running your script, but invaluable when you’re rerunning all the time to debug). The first time Google will double-check with you if you want to run this script, since it’s doing Dangerous Things like emailing people under your name. After that you’re set.

The emails, interestingly enough, will NOT thread/group in gmail. So this is still a rather spamtastic script. _shrug_ I don’t care enough. You can see my testing emails below:

I didn’t choose to use an HTML template for me email. See http://googleappsdeveloper.blogspot.com/2011/10/4-ways-to-do-mail-merge-using-google.html if you want to implement that.

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6.131 Power Electronics Notes

6.131, Power Electronics, has been a blast, even if it’s completely destroyed any belief I have that I can build a functional circuit. Lectures are awesome and Practical Electronics for Inventors is and awesome and completely readable / understandable book.

Here are the main analogies I have learned through 6.131 in terms of relating power electronics to mechanical mechanisms:

Totem pole: because your comparator’s square wave cannot directly drive FETs (not able to source enough currrent)

Boost converter: (e.g. takes 6V and turns into 15V — usu. cannot get it to gain more than 1 order of magnitude). Like winding up a fishing rod (inductor charging capacitor while diode prevents cap from discharging back into inductor), build up power (pool fishing wire behind you), and then release (snap fishing rod forward).
(thus, do NOT hook up without load because it is like winding up the fishing rod and and whacking the wall repeatedly, over and over, at some kHz aka many times per second).

Buck converter: (e.g. takes 15V and turns into variable 0 to 12V). — a switching amplifier (linear amplifier, like 7805, dumps extra power as heat, while switching stores in cap for later use).

transformer trades off voltage and current like mechanical gearbox trades off speed and torque. also, by power conservation, (and used to measure parasitics / Lleak and Lmag), short one side of transformer = short other side, open circuit one side = open circuit other side.
–> todo: reflecting things across the transformer

regulated voltage — a wall wart http://www.ladyada.net/learn/powersupply/ counts, and then can be further filtered ala 2.007 nano carrier with as switching power supply

===== debugging…
Also, circuit debugging things that 6.131 has taught me:

Getting crazy fuzzy on your 74HC delay circuit? (ringing) — check if you have bypass caps, both on your 12v and 5v rails. (For me, connection a cap across pins 14 and 7 didn’t work either, but dropping a cap across 5v rail worked instantly).

2125 debugging: does not required Vdd, merely requires Vcc and the inputs from the delay circuitry. Pin 2: input. Pin 7: output. On high side, measuring directly may not work (get fast flickering or no visible signal) — to measure high side output, stick probe gnd on pin 5 (gnd) and probe in 7 (output). Same for A (which cannot be measured without a load?)
Totem pole drawing max current when your high side signal from the delay circuit is plugged in?

Check that all the grounds are connected.

If you’re at MITERS, check that it’s not a sketchy scope probe / scope problem.

Do NOT build complicated circuits (e.g. control circuitry) straight on the protoboard, no matter how sure you are of building it correctly — you can spend hours  and have a short somewhere and be hard-pressed to diagnose it or rule your control circuit out as the source of your [short, bug]. Build it on the breadboard first — it really is actually must better than protoboard, no matter any concerns about breadboard sketchiness, the faster prototyping time is definitely worth it.

Building the delays and 555s with unclipped resistors and caps may not be a bad idea, since you’ll reuse these circuits and lot but will need to change the values from lab to lab.

Go-kart circuit from lab 2 is reused in lab 3 — make sure you have a working totem pole, or else that will eat unnecessarily into lab 3 time.

Start on the labs early! and ask for help. Even if it seems like a dumb circuit that should just work, if you’re stuck, asking an experienced circuiteer for help will work wonders and you’ll learn a ton about the circuit too, including all the individual parts which you’ll need to know to help anyone else debug and which you wouldn’t pay attention to if you simply breezed through to a working circuit.

your 74HC wants 5V, not 12V!

connect ALL your grounds.

==== misc from this week: lamp ballast:
to find the resonant frequency, you can try to calc by f = 1 / (2*pi*sqrt(L * C)) = (somewhere in 30 to 40 kHz) and measuring the exact L that you actually wound. alternatively, run the FETs on the totem pole (Vdd) at 12v (Vcc for the IR2125’s is 12V and pulled via a wire from the control circuitry, which you breadboarded on a separate board instead of protoboarded straight on the totem pole board, right?) and adjust the frequency (via pot on 555 or whatever you are using to generate square wave being fed into 311 comparator), sweeping the 30 to 40 kHz range until you found where your power supply is supplying the most current. For me, I found the current peaked at 0.38A at 12v at ~32 kHz (and diminishes to either side), while my calculated resonant frequency was closer to 35kHz. This was the magic sauce that led to my fluorescent bulb striking, yay!

also, you want to ground the ERR pins on the IR2125 / totem with jumpers if you want the 2125s to work. The may work without pulling to ground explicitly, but best not even have to worry about it.