Laser Cut Mount for PS3 Eye Toy and Laser Line Scanner

A few years ago I made a 2d line scanner using a webcam and a laser. It worked pretty well but two major improvements needed were the addition of a line laser as opposed to a dot and using a camera with a higher framerate. For version 2 of this project I went with the ps3 eye toy camera which can do 60FPS at 640×480 px or 120FPS at 320×240 px. The camera cost around 10 euros including postage from ebay. The line laser was also bought from ebay for a few euros. It is just a laser diode with a lens which turns the laser into a line. I wanted to design a mount that would hold the camera and laser as well as allow for easy rotation for scanning of rooms etc. The 3D model of the mount was designed in google sketchup and then exported to Inkscape for laser cutting. See below for pictures of the finished mount:


Here is the exported inkscape SVG files:

SVG file available for download here

I made some changes to the design in Inkscape so the 3D model doesn’t match the 2D laser cutting plans. Hopefully I’ll get this up and running in the next week or two. Updates to follow!

Posted in Hardware, laser cutter, Robots, Uncategorized | Tagged , , , , | 1 Comment

Bare bones programming of the TM4c123G ARM Cortex m4 microcontroller

This post will document one possible way of getting an LED blinking with the tm4c123g microcontroller. I’ll be using the TIVA C Launchpad for this example:



A toolchain is needed to compile and link our code. I used this one:
I’m running windows atm so to install this just download and run the .exe and add the bin folder to the path directory and it’s good to go.

For this example I downloaded the TivaWare peripheral driver C library which contains functions for things like setting the clock speed and accessing GPIO pins etc. Download it here

A program to flash the micro is also needed. I went with the LMFLASH PROGRAMMER utility made by TI. It comes with a GUI or you can use the command line. Download it here:
The GUI is nice and simple – pretty similar to the standalone pickit programmer gui.

There is a really handy github repo available here that has a basic blink led example and a makefile. You’ll need the TivaWare library mentioned above to use it.

Step 1:
clone/download the example git repo to your computer. Some slight modification of the makefile is needed, mainly change the TIVAWARE_PATH variable to wherever you installed the TivaWare library. On my computer it’s C:\ti\TivaWare_C_Series-

Step 2:
Compile the example code to make a .bin file, ready to be flashed to the uC. To do this, go to the example just downloaded from github and run ‘make’. It will compile and link the code and store the .bin file in a folder called ‘build’

Step 3:



Open up the LMFLASH programmer utility. Under the ‘configuration’ tab select the TM4C123G Launchpad and then go to the ‘program’ tab where you will be asked to select the .bin file we just made. Hit program and if all goes well you should see the red led on the board flashing! (you may need to hit the reset button first)

Posted in ARM, Development Boards, Hardware, how to, Microcontrollers | Tagged , , , , , | 2 Comments

Scara Arm forward kinematic equation simulator

Source code :

App made using processing version 3 for windows.

float l1 = 12;  //length of l1
float l2 = 9.7; //length of l2

float l1_scaled = 0;
float l2_scaled = 0;

float l_total;

int width = 650;
int height = 650;

int centerX = width/2;
int centerY = height/2;

int circle_diameter = (width - 75);

float angle;

void setup() {
  l_total = l1+l2;
  l1_scaled = (circle_diameter/2)*(l1/l_total);
  l2_scaled = (circle_diameter/2)*(l2/l_total);

void draw() {
  ellipse(centerX, centerY,circle_diameter,circle_diameter);
  line((width/2), 0, (width/2), height); 
  line(0, (height/2), width, (height/2));
  float s_ang, a_ang;
  float ret_vals[] = new float[2];
  float x1y1_vals[] = new float[2];
  ret_vals = mouseXY_2_unitXY();
  s_ang = calc_shoulder_ang(ret_vals[0], ret_vals[1]);
  x1y1_vals = draw_shoulder(s_ang, l1_scaled);
  a_ang = calc_arm_ang(ret_vals[0], ret_vals[1]);
  draw_arm(x1y1_vals[0], x1y1_vals[1], a_ang, l2_scaled, s_ang); 
  text("END EFFECTOR XY", 35,85);
  text("X = " + ret_vals[0], 50,100);
  text("Y = " + ret_vals[1], 50,120);
  text("S = " + s_ang + "degrees",50,(height-50) );
  text("E = " + a_ang + "degrees",50,(height-30) );

float calc_shoulder_ang (float x, float y){
  float shoulder_angle, yx_div, q_ang;
  yx_div = (float)y/x;
  q_ang = acos( (x*x + y*y + (l1_scaled*l1_scaled) - (l2_scaled*l2_scaled)) / ((2*l1_scaled)*sqrt(x*x + y*y)) );
  shoulder_angle = degrees(atan(yx_div) -q_ang);
  return shoulder_angle;

float[] draw_shoulder(float ang, float l1_scaled){
  float angle = radians(ang);
  float[] xy_vals= new float[2];
  float x,y;
  x = cos(angle) * l2_scaled;
  y = sin(angle) * l2_scaled;
  line(centerX, centerY, (centerX + x), (centerY -y) ); //-y due to x-y co-ord system
  xy_vals[0] = centerX + x  ;
  xy_vals[1] = centerY -y;
  return xy_vals;

float calc_arm_ang (float x, float y) {
  float arm_angle;
  arm_angle = degrees( acos( (x*x + y*y -(l1_scaled*l1_scaled) -(l2_scaled*l2_scaled)) / (2*l1_scaled*l2_scaled) ) );
  return arm_angle;

float draw_arm(float xpos, float ypos, float a_ang, float l, float shoulder_ang){
  float arm_angle = radians(shoulder_ang + a_ang);
  float x,y;
  x = cos(arm_angle) * l2_scaled;
  y = sin(arm_angle) * l2_scaled;
  line(xpos, ypos, (xpos +x), (ypos - y)); //-y due to x-y co-ord system
  return angle;

void draw_line(float xpos, float ypos, float ang, float l){
  float angle = radians(ang);
  float x,y;
  x = cos(angle) * 100;
  y = sin(angle) * 100;
  line(xpos, ypos, (xpos +x), (ypos - y)); //-y due to x-y co-ord system

void draw_all(int effector_x, int effector_y) {

float[] mouseXY_2_unitXY(){
  float[] coords= new float[2];
  coords[0] = mouseX - (width/2);
  coords[1] = (height/2) - mouseY;
  return coords;

Look at this diagram to get an idea of what the S and E angles are:

Forward Kinematic Equations:

Forward kinematic equations

Forward kinematic equations

Diagram and equations source :

Posted in Ideas, Processing, scara | 2 Comments

Connecting sensors to the internet using an arduino and a raspberry pi

As part of the PlantBot project, I wanted a way to look at sensor data over the internet. These sensors are moisture, light and pressure. The main one is moisture, the other two were just added in because I had the parts lying around.
Here is a block diagram outlining each of the steps to go from reading the analog sensor values to graphing them on a webpage:



Step 1: Reading sensor values with arduino and sending them over UART:

Sensors used:
-MPX4115A Pressure Sensor
-Moisture Sensor

I made the moisture sensor using some galvanised nails. First just solder some wires to the top of the nails. Then cover most of the nail with heatshrink, just leaving the tips exposed.


The arduino nano has a USB-Serial converter on board so it can be plugged directly into the pi via usb and start sending serial data.


This arduino program waits to receive a serial character from the pi. Once received it will read all of the sensors and send back the sensor values to the pi via uart.

Step 2: Reading sensor values with Python and placing them in a MySQL database:


import serial 
import MySQLdb
import time

db = MySQLdb.connect(host="",    

cur = db.cursor()

port = serial.Serial("/dev/ttyUSB0", baudrate = 9600,timeout=None)

PressureVal = 0;
MoistureVal = 0;
LightVal = 0;

vals = []

while (port.inWaiting()==0):  #keep sending char until arduino replies
vals = (port.readline()).split(',')
print vals
PressureVal = int(vals[0])
LightVal    =  int(vals[1])
MoistureVal = int(vals[2])
cur.execute("insert into sens_vals(Pressure,Light,Moisture) values(" + str(PressureVal) + "," + str(LightVal) +
									"," + str(MoistureVal) + ")" ) #put adc values in mysql db

cur.execute("SELECT * from sens_vals")

#dataset = cur.fetchall()  for debugging - print mysql rows to check sensor values were added	
#for row in dataset:	
#	print row


The MySQL database was made using the terminal on the pi. Here are some pictures of the database format:





On the Pi, a cronjob is used to run the python script every 30 mins. To edit the crontab, I used sudo crontab -e and entered the following:

*/30 * * * * python /home/pi/plantbot/

This means that every 30 mins the sensors are read and their values placed in the MySQL database.

Step 3 : Running PHP on the server to graph values from MySQL database:

<?php // content="text/plain; charset=utf-8"

define('__ROOT__', dirname(dirname(__FILE__))); 
require_once ('../tools/jpgraph/src/jpgraph.php');
require_once ('../tools/jpgraph/src/jpgraph_line.php');
require_once ('../tools/jpgraph/src/jpgraph_error.php');
require_once ('../tools/jpgraph/src/jpgraph_date.php');

$dates= array();
$light = array();
$pressure = array();
$moisture = array();
$i = 0;

 //Check connection
if (mysqli_connect_errno()) {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
mysqli_query($con,"set time_zone = '+00:00'");
$result = mysqli_query($con,"(SELECT * FROM sens_vals ORDER BY id DESC LIMIT 25) ORDER BY id ASC");

while($row = mysqli_fetch_array($result)) {
	$dates[$i] = strtotime($row["date"]);
	$light[$i] =  $row["Light"];
	$pressure[$i] =  $row["Pressure"];
	$moisture[$i] =  $row["Moisture"];


$graph = new Graph(800,500);
$graph->title->Set("PlantBot Sensor Readings");
// Ensure anti-aliasing is off. If it is not, you can SetWeight() all day and nothing will change.
// Use 20% "grace" to get slightly larger scale then min/max of
// data

$graph->yaxis->title->Set("ADC Value");

$p1 = new LinePlot($light,$dates);

$p2 = new lineplot($pressure,$dates);

$p3 = new lineplot($moisture,$dates);





This PHP program looks kinda bulky but most of it is just jpgraph stuff to make the graph look nice. Lines 1-34 is where the MySQL db is accessed and the sensor values read in PHP arrays.

Graph Produced (Real time image):

I’m still working out some of the kinks with jpgraph so while it’s not perfect, you get the idea.
The html page I’ll be displaying all of the real time data on is located at
As I’m writing this post now (10th January 2016), all it contains is a picture of the graph – I’ll be adding to it in the near future.

Update 1 : (10th Jan 2016)
Just planted some cress seeds in part of this plantbox I have – will manually water it (uh effort) for the next few days/weeks or however long it takes for cress seeds to grow. This will be automated soon enough by Plantbot. Stay tuned!

Posted in Arduino, Atmel, how to, Microcontrollers, PHP, Projects, Python | Tagged , , | 4 Comments