Bluetooth Controlled, 3D Printed Sims Plumbob Costume

For the last Purim festivities I made a Sims Plumbob that’s controlled via an android application through Bluetooth to simulate the Sim mood.
In this article I’ll show you what I’ve done and why so you can make one yourself.

The Plumbob

The Plumbob itself was 3D printed. The shape is very simple and it can be modeled very easily, It’s just two hollow hexagonal pyramids glued to each other.
Lazy me didn’t want to start modeling so I found a pre-made model on thingiverse. The shape was perfect and I had the perfect material for the job – a translucent green PLA filament. I chose this material because I wanted to put lights inside that would illuminate the Plumbob in different colors, the material was translucent enough for colors to penetrate and be seen at night and it was green so it would be recognizable in the day, when the lights are not very visible.
The downloaded model has a stem on one side, but it’s not hollow (I needed a stem to mount the Plumbob and it needed to be hollow for electrical wires to go through it). I needed to drill through the stem, which is not an easy task, I ended up breaking it and using another method to secure the Plumbob to its mount.

The Plumbob was printed out of Translucent Green PLA at 190 degrees C. 0.3mm layer height and 100% infill. The print took about 3 hours for each half.

The Mount
I needed a way to mount the Plumbob a few inches from my head, I wanted it to look at night as if it was floating, like in the game. I figured a hair bow with a rod on top painted black could do the trick.
I needed a wide bow for stability, a narrow or thin one would just fall from the weight and movement. I thought about 3D printing a custom mount but I didn’t have enough time to measure, model and make one so I went to the nearest store and tried some bows on.
I didn’t find a wide enough bow, but I found a bow that looked like three bows connected at both ends, it was flexible enough so I can pull them apart to make the whole structure wide enough. Moreover, when I pulled them apart the entire structure was stiffer, less flexible, which is exactly what I needed.
On top of the bow I put a piece of tin I cut to shape with some tin sheers, the tin provides a strong base for the stem and will hold the stretched bow parts in place. I used two part Epoxy glue for all connections.
The stem is an aluminium tube cut to length with the ends split and bent to follow the contour of the hexagon pyramid to be attached to it on one side, and the tin base plate on the other.

Before gluing the Plumbob half to the stem, I spray painted the whole thing black.

I used RGB LEDs for lighting and a 5V Arduino pro mini for control. The Arduino supports about 40mA of current draw from each pin and the LEDs are common Anode and draw about 20mA per color (I used 6 LEDs, that’s 120mA total current for each color of all LEDs on full brightness), so I had to use 2N3906 transistors to switch power to the LEDs (I could have connected each Cathode of each of the LEDs to another pin in the Arduino to avoid the current problem, but the Arduino doesn’t have enough PWM pins and that would require me to modify the code).
To save space on the circuit board, I shortened the Cathode leads of the LEDs and 150Ohm resistors and soldered them together inline.
To make life easier, I made a jig by fixing a 5mm LED bezel with vice grips, this made soldering very easy.

I used a HC-05 Bluetooth module for communication and a U1V11F5 5V step-up converter so I could power the whole thing with 2xAAA batteries.

The Bluetooth module operates at a 3.3V logic level while the Arduino operates at 5V, the arduino would understand the 3.3V from the Bluetooth module fine, but 5V to the Rx pin of the module could fry it. for this I connected the module’s Rx pin to the Arduino’s Tx pin via a voltage divider (a dedicated logic level converter circuit would have been ideal but I didn’t have one nor did I have time to wait for one to arrive).

The circuit had to be mounted to a post made of aluminium tube, so I had to insulate the tube to prevent shorts. The circuit was held in place with zip ties, the LEDs were wrapped around and hot glued in place so that they point in different directions to illuminate the whole shape (in retrospect, I could have used shorter leads for the LEDs).
The aluminium tube was held in place with hot glue and then secured with Epoxy.
The battery holder was mounted on the stem for lack of a better place to put it. I thought about putting it in my pocket with wires running inside my shirt, but they proved to be too long and the resistance was too high so the Arduino would reset when the current draw was high and the voltage dropped.
I needed the batteries on the outside because the power switch was on the holder and I wanted to be able to change batteries. If I had more time I would have probably installed a rechargeable li-po battery inside the plumbob with a small switch and a charging port poking from the side.

Untitled Sketch_bb

The Code
I didn’t have time to write an android application, so I found a free one on the Play Store that fit my needs exactly. There are a lot of applications that do similar things and much more, but this one had a friendly interface and did just what I wanted.
In the description of the app there’s a link to a free example code (and a full code for purchase). I used the free example and modified it to fit my setup.
I also had to use the Software Serial library because, for some reason, the Bluetooth module refused to work with the Arduino’s Serial pins. I used pins 10 and 11 for serial communication with the module (this also allowed me to upload sketches to the Arduino without disconnecting the module).

//pins for the LEDs:
const int redPin = 6;
const int greenPin = 9;
const int bluePin = 5;

#define REDPIN 9
#define GREENPIN 6
#define BLUEPIN 5

#define FADESPEED 5

char serialByte = '0';
#include <SoftwareSerial.h>
SoftwareSerial BTserial(10, 11); // RX | TX

void setup() {
// initialize serial:

// make the pins outputs:
pinMode(redPin, OUTPUT);
pinMode(greenPin, OUTPUT);
pinMode(bluePin, OUTPUT);

Serial.print("Arduino control RGB LEDs Connected OK ( Sent From Arduinno Board )");

void loop() {

// if there's any serial available, read it:
while (BTserial.available()) {
 // look for the next valid integer in the incoming serial stream:
 int red = BTserial.parseInt();
 // do it again:
 int green = BTserial.parseInt();
 // do it again:
 int blue = BTserial.parseInt();

for(i=0; i<3; i++)
 int waste = BTserial.parseInt(); //the app sends data for two sets of LEDs, we don't need this
 // look for the newline. That's the end of your
 // sentence:
 if ( == '\n') {
   // constrain the values to 0 - 255 and invert
   // if you're using a common-cathode LED, just use "constrain(color, 0, 255);"
   // This is for COMMON ANODE
   //red = 255 - constrain(red, 0, 255);
   //green = 255 - constrain(green, 0, 255);
   //blue = 255 - constrain(blue, 0, 255);
   red = constrain(red, 0, 255);
   green = constrain(green, 0, 255);
   blue = constrain(blue, 0, 255);
   // fade the red, green, and blue legs of the LED:
   analogWrite(redPin, red);
   analogWrite(greenPin, green);
   analogWrite(bluePin, blue);

   // print the three numbers in one string as hexadecimal:
    //BTserial.print("Data Response : ");
   //BTserial.print(red, HEX);
   //BTserial.print(green, HEX);
   //BTserial.println(blue, HEX);
   //Serial.print(" "+green);
   //Serial.println(" "+blue);


Additional Thoughts
After the awesome experience with OpenBCI and EEG technology in my previous project, I thought about making this a truly interactive and realistic Plumbob that’ll work in real life. The OpenBCI could sample your brain waves and through machine-learning detect your emotion, this can be then translated into triggers for the Arduino to change the color of the LEDs according to your REAL mood! but that’s a whole other project that will take much more time.

BrainiHack 2015 – Blue GSD with Brain Controlled Labyrinth Game

This weekend (13-14.3) two of my friends (Gal Weinstock and Maxim Altshul) and I participated in the BrainiHack 2015 event hosted at the AutoDesk offices in Israel.
BrainiHack is a neuroscience themed Hack-A-Thon, where makers come to compete in a day-and-a-half long neuroscience-related project building marathon.

My group is called Blue GSD, we are two Communication Systems Engineering students and a Computer Science student. we came with absolutely no background in Neuroscience and tried to make something awesome. We brought an arsenal of tools, electronic components and a home-built 3D Printer.
We ended up winning the special OpenBCI prize for the best project in the open source category. The prize was an OpenBCI Starter Kit valued at 500USD.

Our project is a Labyrinth game controlled via brain waves (EEG). We are using OpenBCI, an arduino based open source bio-sensing microcontroller, It’s brilliant and with some initial assistance from Conor, one of the founders of OpenBCI, it’s really easy to work with.

The Labyrinth
The game itself was entirely 3D printed, it’s movement is provided via two micro servo motors controlled with an Arduino Uno.
The mechanism consists of three nested frames that are anchored in different places to achieve two degrees of freedom – roll and pitch.
We had no time for strong glue and I didn’t want to make any permanent connections (I’m designing on the fly so a lot can go wrong, and some did) so my design had to be zip tie friendly, the motors and motor arms are all attached with zip ties to the frames. The hinges are M3x16 screws and nuts with some washers to keep the frames in place relative to each other and press them onto the motor.
In the end we noticed we didn’t have enough clearance under the device for the frames to move all the way and we had no time to print another outer frame, so we had to make lifters for the legs which actually worked out perfectly.
Models for all 3D printed parts can be downloaded free at

As mentioned before, OpenBCI is an open source EEG device (and more, but that’s not relevant right now, I might explore more of it’s capabilities in the future) which was handed out to whoever wanted to use it.
With OpenBCI we could attach electrodes wherever we wanted (as opposed to some of the other fixed position alternatives), that way we could experiment with different methods and brain waves and choose the ones that work for us.
Conor from OpenBCI was kind enough to give us a little guidance and showed us another project done with OpenBCI, a five-person controlled shark balloon by chip, from which we learnt a lot about the system.
In addition to all of its advantages, it’s Wireless! It includes an RFduino that transmits the data to a dedicated USB dongle that plugs into the computer.

Brain Waves
We wanted to explore more than one type of brain waves. The shark balloon project was based purely on Alpha waves, a 7.5-12.5Hz wave our brain produces in the Occipital Lobe when we close our eyes and relax, that’s neat but we wanted more. Alpha waves are very easy to detect but there’s only one type of Alpha wave per person, this means that in order to control 2 axis we would need 4 people or 2 if we use direction toggling (more on that next).
After some research we found out about SSVEP (Steady State Visually Evoked Potential), a phenomenon where the brain produces a frequency (and/or harmonies of a frequency) that matches the frequency that excites the retina. This means that if we look at a light that blinks at a constant frequency, the brain will produce the same frequency. After some experimentation, we found that the range 5Hz-20Hz was easiest to detect and that 16Hz was far enough from the Alpha waves so they don’t get mixed up.
By combining Alpha and SSVEP we have 2 types of waves we can control and anticipate, which gives us the ability to control the game with just one person.

Controlling the Game
The problem with this technology is that it’s very slow, it’s not real-time by any standard. It may take a few seconds for the wave to generate and be detected while the Labyrinth game requires finesse and delicate movements to balance the ball, this is impossible with 2 or 3 second delay between reaction and actual movement of the platform.
To overcome this challenge we decided to simplify the game, instead of continuous control of the position of the platform, each axis would only be fully tilted to one side or the other, for this to work we created a super-simple maze layout, no holes, no balancing, just walls with straight angles.
As mentioned, we wanted to control the whole thing with one person and we had two different signals we could extract. Left-right position toggle was controlled via Alpha wave and up-down position toggle was controlled via SSVEP.


Data Analysis and Translation
OpenBCI provides a neat GUI that allows you to visually see the data and analyse it more easily. The interface provides time-domain and frequency-domain (FFT) graphs as well as a map of the head with electrode activity.
Once the data is captured with OpenBCI, it is transferred to the computer for analysis, the computer runs a Processing program that computes the Fourier Transform of the signal over a defined interval of time, filters the spectrum to look at relevant frequencies and finds the most powerful frequency in the range. If the peaked frequency is the one we are looking for, a command is sent to an Arduino board via serial port. The Arduino then controls the servos according to the command received.
In our project, we were looking for peaks at around 10Hz (Alpha) and 16Hz (SSVEP) and had to ignore the very high peak at 50Hz that is caused by the AC power frequency here in Israel.

Screenshot from 2015-03-13 13_27_35

The code running on the computer is a modified version of the shark baloon’s code. Since they already figured out the Alpha wave capturing and translation, we had to modify it for one person (they used 5) and add the SSVEP frequency capturing. The shark balloon code was taken and modified from another project (which modified the original code from OpenBCI) so it’s already a little messy and we probably made it messier (with a day and a half to get the whole thing to work we had no time to waste on making it pretty).
The code running on the Arduino is fairly simple, just a loop polling input and controlling the servos. We made the servo movement slow and continuous so that the ball doesn’t jump around.
The code will be uploaded to GitHub in a few days.

Special thanks to Conor over at OpenBCI for helping us and introducing us to the technology.

Building The 3D Printer

Well, I didn’t document the whole building process because there are A LOT of guides and documentations out there. Plus, it would have slowed me down considerably.
This is written after the fact, obviously.

This project is not completely finished and it might never be. I see it as an evolving project, I constantly add features and change stuff.

Most of the parts were ordered off eBay.
The frame is Dibond Aluminum. That’s plastic with aluminum layers on both sides, it’s supposed to be light and strong – it is.
All plastic parts are 3D printed and came with the frame (the whole idea of the RepRap project is self-replicating 3D printers, well not fully, just the plastic parts – the goal is to get a better printed to non-printed parts ratio)
The hot end is an E3D v6 all aluminum hot end.
The motors are Nema 17 stepper motors, they are a little less powerful that the “standard” 0.4Nm ones, but they work perfectly fine.
The controller is an Arduino Mega 2560 paired with a RAMPS 1.4 driver board.
I’m using a standard 500W computer ATX power supply.

The initial build took about about 3 days. It took place during the last summer at my house with a few of my friends who wanted to help and see the wander.
The build itself wasn’t special, just a marathon of wrenching, drilling, measuring, soldering and calibrating. Oh, and pizza. lots of pizza.

I think the most exciting moment was seeing the code and motors work together. It’s not something I haven’t done before, nor was it an advanced part of the build, but seeing the pile of metal and plastic turn into something that follows commands other that the trivial “stay” was just beautiful and a sign that the hardware is fine and we are on the right track.

After 2 and a half days we had a kind-of-working 3D printer. a diamond in the rough, one might say.
It extruded plastic and moved in the right direction, but it needed calibration and lots of it.

On the evening of the 3rd day I did some work alone and kept having the same problem – I could print fine at first, but after letting the printer rest it would not extrude more plastic, every time I had to disassemble the hot end and drill out the stuck plastic.
It’s too long of a story for this post (maybe I’ll post another one with the fully detailed comedy) but I’ll give you the recap of what I learnt – Computer thermal compound is not intended for these temperatures and if your hot end came with a little fan – use it.
I ended up breaking my hot end in so many places I had to buy a new one.

The new hot end took a little time to arrive and when it did, the semester had already begun and this one was brutal, papers and assignments every week in every course. I never thought I’d wish for midterms to come sooner, Argh..
I could only invest a few hours a week for fiddling with the printer but slowly and surely, it’s up and running.

3D Printer

Yeah, so I built a 3D Printer.

I have been fascinated by 3D printers for a while now, I’ve always wanted to build one. The notion that you can think of ANYTHING and make it a reality AT YOUR DESK with not that much of an effort – if any, blew my mind.
I read a lot and followed some really cool project only to be overwhelmed by the complexity and scale of the project (which turned out not to be that complicated), thinking that if I start I might get bored or worse, stuck, and leave it half finished.

So what made me go through with it?
One day, I was sitting at a friend-of-a-friend’s house talking about projects and DIY. I mentioned how I always wanted to build a 3D printer or a CNC machine and Gal, the one who lives there, said he built one a few years back and missed it. We decided to build mine together.
He also mentioned he wanted to get into programming with Arduino, with which I was quite familiar, so he helped me choose components for the printer and I helped him build an Arduino starter-kit. Win-Win.

Here I will share my journey, thoughts, lessons and updates revolving around building, maintaining and operating my 3D printer. Enjoy.