TESZ weblog

Interfacing Hokuyo URG [C#]

noreply@blogger.com (Trin Ketpratoom) — Sat, 04 Aug 2012 19:50:00 +0000

I haven't update my blog for so long. It's time (I guess).

Back to last few weeks I have been played with new expensive LRF, Hokuyo URG-041LX.

My first word was WOW, "How the hell do you get that?" I asked my professor.

He just simply smiled and said "Make sure you can use it", and yes I have to say this is a big one.

UI written in C# (WPF)

As always, first I need to know more about this laser-range finder. This isn't so hard, all I need to know on Hokuyo's site.

Briefly, This sensor interface by RS232 with protocol called SCIP2.0 and very high current consumption.Test command by request version (VV command) through serial port (57600 baudrate).

Now I know it's working, next step is to get data from it (GD command).

This is obviously encoded.
Hokuyo's decode protocol described in below picture.

Many of examples written in C++ (with QT). I don't want to use that because I lack of skill on C++, better be in my field (C#). But that doesn't mean I can't read C++.

This is what it's look like in code.

Now I can get "range" and "angle" of detected obstacle.
This isn't too hard, the hard part is using it. My goal is create map from robot.
And how I do that? I need to generate map from obstacles then localize the robot position. This problem called SLAM(Simultaneous localization and mapping).

The solution right now is trying ROS(Robot Operation System) or MRPT(Mobile Robot Programming Toolkit). But I still have time so I decided to do it my self with my robot, whatever it takes.

The first picture is currently my work (Detection landmark in each scan), Next step will be implementation of IMU with this project. So robot can realize its direction and calculation with landmark will generate map.
The last step is when robot move, How do it really know where is it?
Hope this helps for all beginner like me.

How to drive MOSFET from mcu 3.3V/5V

noreply@blogger.com (Trin Ketpratoom) — Sat, 21 Apr 2012 21:21:00 +0000

As you know, when you want to turn-on MOSFET you will need 10-20V across Gate and Source for charging internal capacitor in MOSFET. Moreover, the current needed to trig Gate must high enough to turn this thing on.
And when the MOSFET turn-off, it needs to drain current in internal capacitor off in time limit.

Let's jump to the point. We want to use MOSFET as switch electronic to turn-on/off some LOAD (such as solenoid). First we determine a current of Full-Load, I say 10A.
IRFZ44 has been selected because of current limit so high about 50A.
Then we come back to driver circuit with these qualify.
1. Isolated signal ground and power ground for protection.
2. Driver circuit operation on vary frequency at least 10KHz.

Here is a schematic.

R5 100K is used to drain current when turn MOSFET off.
D2 zener diode 15V make sure Vgs isn't over 15V.
Using TLP-250 from Toshiba to isolated ground. This chip is very impressive, designed to be a gate driver mixed with op-to technical.
C1 100pF is filtering capacitor.

This circuit works perfectly in my job (turn-on/off Solenoid).
Hope this help!

Quick Startup: MACH3 configuration STEP BY STEP

noreply@blogger.com (Trin Ketpratoom) — Sun, 15 Apr 2012 22:41:00 +0000

After what I said here, make sure MACH3 driver is all set and we're ready to go.
I usually not have much a free time, so shall we?
Remember one thing. This is a tutorial, you need to watch and learn, I cannot assure what I did will work for everyone.

First, we need to setup "Ports & Pins" for communication between MACH3 and circuits.
Select config -> Ports & Pins.

As you can see, I prefer "Active Low" rather than "Active High" because of noise. In this dialog you can setting your "Step Pin" and "Dir Pin" for your motor each Axis.
Next step will be setup "Limit switch" and "Home switch".

You can test Limit switch by pushing it, MACH3 screen will notifying "THE EMERGENCY" call.
If this happen then we good to go.
The next part is very important. We will tuning Motor for precision and accuracy.
Select config -> Motor Tuning.

Significant variables are "Steps Per" "Velocity" and "Acceleration".
"Steps Per" is how many steps of pulse from MACH3 to move lead-screw for 1 unit.
"Velocity" is a speed of-course, velocity needs your ear to listen for what happening to your motor then adjust it appropriate.
"Acceleration" is adjusted by shaping the curve into trapezoid.
The key is adjust "Steps Per" into right value, this link seem to be good enough for how you calculating "Steps Per".
But actually I recommend to automatic setup by MACH3 itself.

The important thing is "Steps per" must be correct, otherwise your CNC will be inaccurate and don't reliable.

Auto detect serial port in WPF (C#)

noreply@blogger.com (Trin Ketpratoom) — Sat, 14 Apr 2012 20:57:00 +0000

well, I was struggling in C# programming for a while. What's bother me is UI system. I have to confess I really fucked when it's come to deal with display system.
That is why I came to study WPF for good.

Let's turn this ship back. I want to detect USB port, so I'm gonna try to handle "Window Messages" then figured out how to code in WPF.
This is not a really problem because this blog (by Andrew Eichacker) is save my ass today, thanks to him.
Now I can screwed with "Window Process" and "Window Messages". Let's go!

Firstly, according to Andrew Eichacker's code, we call SourceInitialized event to build a way to handle WndProc.

Secondly, check the msg for what we looking (WM_DEVICECHANGE) see this page
Then we can add currently Serial Port that occur in the system.

Finally, remove the hook we made.

That's it, when plug your USB-to-Serial Port this program will received WM_DEVICECHANGE and process automatic.

PS. don't forget to add "System.Windows.Interop" for WindowInteropHelper.

My asus N43 got problem: "System Interrupts" CPU 20%

noreply@blogger.com (Trin Ketpratoom) — Sat, 25 Feb 2012 21:07:00 +0000

lately when I'm coding some application with Visual Studio 2010 (got it for Free with my student license XD) and suddenly VS's window going to lag/stun for 1-2minute (my feeling is forever). This behavior show a lot lately, so I decide to open task manager.

Task manager at the time.

At first time I thought it was some kind of virus. Why is that? see "CPU Usage" and take a close look at "Process list" that sorted by "CPU" DESC. You will see ordinary process list but, why CPU going up to 29% (What the H..).
I'm so curious about how is this happen. Then, I open "Resource Monitor" to monitor what mystery resource is using 28% of my CPU.

And I found the problem, It is "System Interrupts". So I ask a question to my professor (Google) about "System Interrupts". I got plenty of answer and one of it's talk about Device Driver, about how driver bla bla bla. If you want to know please go knock your self up.

I decide to try to disable each driver one-by-one and check CPU usage behavior. Try to find out which driver is make me in trouble. And finally after all 2hours I still got nothing (and my mind is start thinking about why people always bullshit).

I'm going back to diagnostic and may be it's not Driver, it is BIOS who has a problem. Which instruction here, I'm going to flash BIOS (with EasyFlash) and FINALE! my "System Interrupts" is gone! THANK TO GOD (twice).

In conclusion, this problem is unique problem that's mean each PC/Laptop will face this problem differently. Some PC is "Sound Driver" problem, some is "Graphic Driver", but my problem is BIOS. So don't give up, check every driver and firmware of your computer. Reading more than doing, don't lazy to do research.

Many of life's failures are people who did not realize how close they were to success when they gave up -- (Thomas Adison).

Good day!

Mach3 tutorial: Preparation Software

noreply@blogger.com (Trin Ketpratoom) — Wed, 15 Feb 2012 09:22:00 +0000

Mach3 is PC-based CNC software well-known in many industrial. Let's cut to the chase to Mach3 setup.

Firstly, take a look on system requirement here. My recommended OS is Window7-32bit, it's have to be 32 bit for avoiding several problem. Secondly, download Mach3 software Demo here, select Lockdown version for more stable than Development version. Using cracked software is very dangerous if you use this program for study or hobby, Demo software is better choice, but demo software is limit to 500 line of G-Code.

Thirdly, change your Regional and Language in PC to English(US).

Change Region and Language to English

Finally, install Mach3 software, make sure your computer found Mach3 Driver.

Mach X Pulsing Engines driver

And that's it, software preparation is complete. if your PC isn't recognize Mach3 driver, check your PCI/LPT port.

I'm run out of time, so next article will discuss about how to config mach3 and hardware relevant. If you want this work, you have to understand both side of software and hardware.

My first post!

noreply@blogger.com (Trin Ketpratoom) — Wed, 08 Feb 2012 02:58:00 +0000

Hello world, this is awkward moment I swear. First I should introduce myself and my name is Trin Ketpratoom. I'm 22 (at 2012) and single, girlfriend register is opened.
I'm interested in Programming(C++,C#, WPF), Micro-controller(dspic, FPGA, STM32) and other engineering stuff.
My currently university is KMUTNB (King Mongkut's University of Technology North Bangkok) originally known as "Thai-German Technical School". I'll undergraduate in electrical engineering this year if I don't screw something up. My senior project is X-Y Table development, I prefer to call it "CNC".

This is my weblog and it will write about me and what I do. I cannot assure this weblog will be not boring forever but I can say one-thing is I'm trying.

My senior project examination is coming, this is disaster for everyone. I think it's time to work (Boringgg XD).