Just Sharing Knowledge on Robotics, Electronics and Programming

Sunday, August 26, 2018

[SOLVED] Xamarin Studio Android SDK Not Found ... Searched Windows Registry

If you use Xamarin Studio For the first time, i suggest you to create a very simple apps that is two click. then test your project. if you face the following error :

SetUp : System.Exception : Android SDK not found. Please install it and if it is still not located, please set the ANDROID_HOME environment variable to point to the directory.
Searched locations:
Windows Registry
(No path) - Not set. [ Source: ANDROID_HOME ]


SetUp : System.Exception : Java Development Kit (JDK) not found. Please make sure that it is installed and if it's still not located, please set the JAVA_HOME environment variable to point to the directory.

Searched locations:Windows Registry
 [ Source: JAVA_HOME ]

then use the following solutions (see the picture),
1. Go to this pc and Right -click then click properties

Friday, August 24, 2018

[SOLUTION] Select Database The N numbers Last or First Rows in Codeigniter

If you want to select the N last rows or N first rows, in codeigniter you can use the following script

$n = 100;
$this->db->order_by("id", "desc"); // N last rows 
$query = $this->db->get('my_table');
$myRow = $query->row();
$n = 100; 
$this->db->order_by("id", "asc"); // N first rows 
$query = $this->db->get('my_table');
$myRow = $query->row(); 

Friday, August 17, 2018

[ Research ] Autonomous Land Vehicle In Progress

We are currently research the Automomous Land Vehicle in Institut Teknologi Sumatera, Indonesia. The Autonomous system is using GPS to obtain location of vehicle and using PID control in steering system and position tracking system.


The progress of research is still 40% complete. we are still researching in control and web based control station.

Tuesday, August 14, 2018

[SOLVED] HMC5883L not working ( i2c adress:0x0D instead of 0x1E )

do you buy HMC5883L but the device not working?
if yes, you should check the i2c adress by using i2c scanner. --link--

if in i2c scanner you found device address is  0x0D then your trouble is wrong library, but if terminal say i2c not found, the problem is on hardware connection.

if address is 0x0D this is different with hmc5883L because this module is using qmc5883L ic. so the library is different with hmc5883L library.

To solve this issue, you can use the following library to work with your compass module.

Download Qmc5883L library

Wednesday, June 13, 2018

[SOLVED] How to move Application Folder to the Basepath (root) in Codeigniter

Codeigniter Application folder is where our job begin, the default structure of codeigniter is


now you want to move your application content to the site, you can use the following way

in index.php :

on line 117 change value to empty then

$application_folder = '';

and in line 239 change from

if (is_dir($application_folder))


if ($application_folder=='')


Tuesday, June 12, 2018

How to Start Learn PLC (Programmable Logic Controller)

PLC is a device that is used in most industries in the world to control of system in industry. For electrical engineering that focus on control system PLC is a device that has to be learned. Then how to start to learn PLC? if you have device, you can start by programming the device. but what if you didnt have the PLC? you can start by simulation. 

PLC Fx Trainer

What is the best simulator that can be used? there are many PLC Simulators that can be used, and also there is Online PLC simulator. but i recommended to use Mitsubishi PLC Fx-Trainner, this software has great simulation tools and 3D simulation of industry devices. You can download PLC Fx Trainer by searching on google and start the learning

Solve Mathematical Problem Using Web App

Have you ever found a math problem that is need to be solved quickly? sometime, we need to know how math problems is solved for example when you in college or in school, but in another case, you only need to know the answer quickly without knowing how it done. There is some tools which can help you to solve math quickly. 

1. Matlab
Matlab is premium software that that have a great ability in Math problem, for example in Control system simulation, matrix , laplace, fourier, bode plot and etc. this application is available in Windows, Linux and Mac OS. 

2. Wolfram Alpha - Link
This is the recommended for you who need quickly solution of math problem, because wolfram alpha is web based app that free to use. you can get the Math Solution such as :
a. Laplace
b. Integral
c. Elementary Math 
d. Plotting Graph
e. Trigonometri
f. and so much more