Rediscovering 3d CAD because of 3D Printers


This past week (maybe 2) I’ve been utterly obsessed with 3D printer stuff. It has gotten me excited about 3D drafting and CAD all over again. Simply because you can create a 3 dimensional object on a computer in a matter of minutes or hours and render it to look completely realistic, but now because of 3d printers you can actually make those objects (if you so wished)! Awesome!

Yesterday and Today I’ve been playing around with Solidworks again. My ancient 2007 version of solidworks. lol. But it works non-the-less. Although i’d love to try out Autodesk 123d Design (which is free). But, why oh why are there still no good CAD programs that run nativity on Linux. Especially if you have a Mac version. If it runs on Mac it can easily be ported to Linux. Why do you think the Arduinos and the rep-raps, and open-source, and so many other great things have taken over the world by storm? Yes it’s because they are great products, but also because they are cross-platform! Okay, End-Of-Rant.


But Seriously, i actually really like designing something in CAD if it’s something i’m excited about. Today i ventured into the realm of something relatively simple, test tube racks. But sadly there are not currently very good designs for test tube racks available. Which actually surprised me. The three best places I look for pre-made CAD files are at 3dContentCentral, which is the oldest site of this kind that i ever encountered. It is mostly for people who use solidworks, but the great thing about the site is that it has a tool that can convert to and from many different CAD formats, including solidworks formats, IGES, STEP, STL, etc. The second is GrabCad. GrabCad is a new community also aimed at engineers sharing CAD models freely. It dosen’t have the nice file converter that 3dContentCentral has, but it has a vibrant community that provides feedback, help, and will check out your designs. Someone on GrabCad actually helped render the nice  looking wood rendering of my 1950s style test tube rack. How nice! Thank You! And the third is the famous MakerBot Thingiverse. Thingiverse is less focused on CAD formats and instead is focused on creative designs optimized for 3D printing. At minimum an STL file will be available for anyone to download and print on any 3d printer they have access to. I currently dont own my own 3d printer, but am currently using the Lulzbot mini that currently resides at my local library. How’s that for public access?!!


So these are the three test tube racks i modeled today in Solidworks. Not super amazing i suppose, but i’m proud of them. My favorite is the nice wooden 1950s style test tube rack. I partly chose to start with that one because i have one that looks just like that looks like it was made by a monkey in china. It seriously is not as nice as my virtual one and not anywhere near as fancy looking either. But also because it is the standard test tube rack featured in the banned 1960s DIY chemistry book: The Golden Book of Chemistry Experiments. It was just begging to be brought into the modern world.

I then ventured into modeling a simple test tube rack because there were none available that i liked. I may make a smaller version of this one for 3d printers that have small print beds. Perhaps one with only 4 test tubes.

The last one i modeled after a nice round plastic test tube rack I’ve seen on the internet. I don’t have one, but I’ve been meaning to buy one. But i wanted to model one in Solidworks and create one that fit on a Lulzbot mini 6″ X 6″ print area that other people could print out too. So i made one of appropriate size and then made it able to split in two to be printed easily. I really like how the design came out. I hope to be able to test it out by printing my own sometime.

1950s Style Test Tube Rack:


Economy Style Test Tube Rack:


Round Mini Test Tube Rack:



Interfacing Vernier Sensors and Arduino (and vice-versa!)

So, recently I’ve been bored. That’s nothing new really. The up side to the times when i get really bored is that i usually end up starting some sort of electronics project. Since i have an interest in the DIYBIO movement and an interest in DIY chemistry i have realized that it’s really cool (and helpful) when you can use sensors to collect your data. But up until now i haven’t had the motivation (or the money) to really dive into it. But today’s post may be the beginning to turning that tide.

Awhile back i stumbled across this post by David Hay, after noticing this question on adafruit. In it he tinkers a bit with interfacing an older vernier (light?) sensor with an arduino clone.  Since i use vernier sensors in my chemistry classes at school i have come to love them. I wondered if i could do something similar, but what i really wondered was whether i could do the opposite as well. Could i interface other non-vernier sensors (like sparkfun sensors) using an arduino to the fancy LoggerPro software or my TI84+ calculator? It turns i can!


The LoggerPro software is really good stuff, but i’m cheap whenever i can be. That’s one reason i thought of my TI84+ calculator. I already have one of those, and vernier has released free software for it that can graph data from vernier sensors in real time. The program is called EasyData and can be downloaded here. The second option is to use LoggerPro on Linux. And since i’m already a full time Ubuntu user i get to use the newly updated free LoggerPro beta for Linux! Sweet Beans!


I’ve already tested both. They both work great. The cool thing is that i was able to hook an arduino to my calculator EasyData program and also LoggerPro on the computer by using a Vernier EasyLink (with an adapter to convert it into a GoLink). I had to get a Vernier Analog Breadboard Cable for it to work, but it was well worth it. I sent some test pwm values using the Arduino example code for the fading led on arduino digital port 9. I used the example pdf from the DIY Light Intensity Sensor example project on the Vernier website to help me out a bit.


I was also able to do the opposite like what David Hay did with his sensor. I was able to successfully interface a stainless steel temperature probe from Vernier (which is basically just a thermister in a nice case) to my Arduino. I used the example pdf from the DIY Build a Temperature Sensor example project to help me out, along with the values in an equation provided in the manual that came with my stainless steel temp sensor. I also bought this nice Analog Proto Board Connector from vernier which allowed me to do this so quickly. Here is the code i used on my Arduino to calculate the temperature from this thermister.

int led = 13;

#include <math.h>

#define ThermistorPIN 0 // Analog Pin 0

float vcc = 4.91; // only used for display purposes, if used
// set to the measured Vcc.
float pad = 15000; // balance/pad resistor value, set this to
// the measured resistance of your pad resistor
float thermr = 20000; // thermistor nominal resistance

float Thermistor(int RawADC) {
long Resistance;
float Temp; // Dual-Purpose variable to save space.

Resistance=((1000 * pad / RawADC) – pad);
Temp = log(Resistance); // Saving the Log(resistance) so not to calculate it 4 times later
Temp = 1 / (0.001129148 + (0.000234125 * Temp) + (0.0000000876741 * Temp * Temp * Temp));
Temp = Temp – 273.15; // Convert Kelvin to Celsius
Temp = Temp / 2;

// BEGIN- Remove these lines for the function not to display anything
//Serial.print(“ADC: “);
//Serial.print(“/1024”); // Print out RAW ADC Number
//Serial.print(“, vcc: “);
//Serial.print(“, pad: “);
//Serial.print(” Kohms, Volts: “);
//Serial.print(“, Resistance: “);
//Serial.print(” ohms, “);
// END- Remove these lines for the function not to display anything

// Uncomment this line for the function to return Fahrenheit instead.
//temp = (Temp * 9.0)/ 5.0 + 32.0; // Convert to Fahrenheit
return Temp; // Return the Temperature

void setup() {
pinMode(led, OUTPUT);

void loop() {
float temp;
temp=Thermistor(analogRead(ThermistorPIN)); // read ADC and convert it to Celsius
Serial.print(“Celsius: “);
Serial.print(temp,1); // display Celsius
//temp = (temp * 9.0)/ 5.0 + 32.0; // converts to Fahrenheit
//Serial.print(“, Fahrenheit: “);
//Serial.print(temp,1); // display Fahrenheit
digitalWrite(led, LOW);
delay(1000); // Delay a bit…
digitalWrite(led, HIGH);

So what does this mean? I think this opens up a whole new world of possibilities. On the one hand i believe i can now use the nice Vernier LoggerPro or EasyData real-time graphing software to interface non-vernier sensors like Arduino boards directly and perhaps others like a Sparkfun Alcohol sensor? (which i have one i would like to try) This should make it easy to interface cheap sensors in chemistry and biology labs that already have vernier equipment. I think it also means that we can now easily use Vernier sensors on non-proprietary devices such as cheap Arduino micro-controllers.

I also look forward to soon tinkering with using an Arduino webserver as a different real-time sensor graphing and data logging device. I hope in the future i can help to create other tools which might be useful for DIYBIO and other DIY science.

Tabelo de la Kemiaj Elementoj

Esperanto Kemia Perioda Tablo de la Elementojn
Esperanto Kemia Perioda Tabelo de la Elementojn.


Mi finis tradukanta tio versio de la “Perioda Tabelo de la Elementoj” en Esperanto hieraux. Mi decidis uzi la vorto “Kaliforniumo” kaj ne “Kalifornio”, sed “Kalifornio” estas tre mallonge. Mia esperanto ne bonega, do bonvolu diri al mi, ĉu se mi tradukis vortojn malĝuste.


I finished translating this version of the Periodic Table of Elements into Esperanto yesterday. I decided to use the word “Californium” instead of “Californio” even though the second one is much shorter. My Esperanto isn’t that good, so please tell me if i translated anything wrong.

Chemistry in Esperanto

 Kemio en Esperanto

Gxenerala, Organika kaj Biologia Kemio
Gxenerala, Organika kaj Biologia Kemio

Success! Well, okay… only a minor success, but still. I finally managed to track down a PDF copy of “General, Organic, and Biological Chemistry” in Esperanto (Gxenerala, Organika, kaj Biologia Kemio). Yes Finally! After months of trying to track it down on the internet. I finally contacted an Esperanto speaker in Columbia, who gave me a link to the only working torrent.

Sukceso! Bone, okaj… nur malgranda sukceso, sed ankoraŭ. Mi fine sukces ..mi trovis .PDF kopio de “Ĝenerala, Organika, kaj Biologia Kemio” en Esperanto (Gxenerala, Organika, kaj Biologia Kemio). Jes Fine! Post monatoj de provanta spuri ĝi en Interreto. Mi fine kontaktita Esperantoparolanton en Kolumbio, kiu donis min la korekto ligon por torento.

I originally found out about that book (Gxenerala, Organika, kaj Biologia Kemio) after doing a random search about the -ENZO suffix, and how it originated. That search led me to the reference to the translation of the book by the Chicago Esperanto Society. So, logically you would think that by contacting the Chicago Esperanto Society, would pave way to obtaining a copy…

sakarozo, glukozo kaj fruktozo
sakarozo (sukero - sukrozo), glukozo kaj fruktozo

…NOPE. They had never heard of it, nor had any copies. I’m not sure why it was so hard to track down, but alas i’m happy i found it. Now the work can continue on being able to translate Penumbra Overture into Esperanto. And eventually my original goal of translating the Golden Book of Chemistry Experiments into Esperanto as well. I’ve already translated the cover. It reads “La Valora Libro da Kemiaj Eksperimentoj”.

Valora Libro Da Kemiaj Eksperimentoj
La Valora Libro Da Kemiaj Eksperimentoj

I’m still not that great at Esperanto, and still haven’t learned enough about the grammar, but I’m getting better at as time goes on.

and here is an interesting demonstration about combustion in chemistry by Daniel Solomon.

Kaj tio estas interesa klarigo de bruligxo esperante en kemia fakultato de Varsovia Politekniko je 14/12/07 de Daniel Salomon.