PIR Motion Sensor + LCD Screen + Arduino Uno

For one reason or another, I've recently had the urge to follow in my father's footsteps and start tinkering with electronics. He's basically a wizard. He has fixed a lot of appliances that others tossed out the door without the slightest bit of investigation. I think he did this with the monitor I had hooked up to my very first computer. He just popped open the case, found the problem, soldered some solution in there, and that monitor worked for probably a decade afterwards. Amazing stuff.

Anyway, I have an itch to create a laser trip wire (don't ask). I took a basic electronics class my freshman year in college, so I am already familiar with resistors, capacitors, ICs, breadboards, soldering, etc. It doesn't seem like a very daunting task to create that trip wire, but I'm starting fresh with electronics (it's been a good 8 or 9 years since I last soldered or anything like that).

One of my co-workers mentioned the Arduino as something to get me started on the trip wire, so I started doing some research here and there. The more I read, the more excited I got. I wanted soo badly to buy all of the junk that I'd need to start tinkering with an Arduino, but I didn't think my wife would appreciate that--especially around Christmas time.

Several of my awesome relatives sent me very generous gift cards for Christmas this year, which finally gave me the opportunity to buy a load of stuff for the Arduino without feeling bad. So I ordered loads of stuff. Most of it is here, some of it is still on its way. My Arduino Uno arrived around noon today, and I haven't been able to stop tinkering! It's really a lot of fun, and stupid easy even if you're not a programmer!

I started with the basic "oooh, blinking LEDs!" sort of projects (or "sketches" in Arduino parlance). Then I moved on to tweak those to work with multiple LEDs. There were a few different scenarios I ran though because two of my LEDs weren't lighting up very well. I guess I either hooked them up wrong or I didn't seat them properly... whatever.

The next project was when I hooked up a PIR (passive infrared) motion sensor ($9.99 at RadioShack) and installed a demo sketch that I found on the Arduino wiki. I wasn't quite sure how to wire everything for the PIR sensor, so I took a look at this Make Magazine video to see one way of setting up the circuit. That one simply lights up an LED and makes some noise. I just made mine light up and LED since I don't have a buzzer (yet).

Next I moved on to the LCD. The package came with a 20x4 green-on-black backlit LCD display, a 2.2k Ohm resistor, and a set of pins to connect the LCD to my breadboard or whatever. I actually soldered the pins onto the LCD display board (wow, was that even more difficult than I remember!) so I would have less of a hassle getting all of the contacts working. Getting the LCD to work was pretty easy after that.

Then I took those two projects a bit further. I'm certain others have done this years ago, but I didn't use a sketch that was completely written for me this time so I felt special enough to share :) I added the PIR circuit from before less the LED, merged pieces from both demo programs, and came up with a motion sensor that would flash "INTRUDER ALERT!!" on the LCD screen a few times when triggered. Based on my testing, the sensor works extremely well (once calibrated!!), and it will detect motion well across the open area of my apartment (maybe a bit further than 20 feet)!

I'm quite happy with my work, especially for not having "dealt with" electronics for such a long time. When I tried to share my success with some of my friends, they wanted a video to prove I'm awesome (I guess?). So here it is. Trust me, I know the video is horrible--I speak too quietly (baby sleeping in next room), I stumble over my words (that's just me), and I neglected to even offer you some music to rock out to as I blabber about this stuff.

Here's the program I wrote/modified:

  * //////////////////////////////////////////////////
  * //making sense of the Parallax PIR sensor's output
  * //////////////////////////////////////////////////
  * Switches a LED according to the state of the sensors output pin. Determines
  * the beginning and end of continuous motion sequences.
  * @author: Kristian Gohlke / krigoo (_) gmail (_) com / http://krx.at
  * @author: Josh VanderLinden / codekoala (.) gmail (@) com / http://www.codekoala.com
  * @date:   3 Jan 2011
  * kr1 (cleft) 2006
  * Released under a creative commons "Attribution-NonCommercial-ShareAlike 2.0" license
  * http://creativecommons.org/licenses/by-nc-sa/2.0/de/
  * The Parallax PIR Sensor is an easy to use digital infrared motion sensor module.
  * (http://www.parallax.com/detail.asp?product_id=555-28027)
  * The sensor's output pin goes to HIGH if motion is present. However, even if
  * motion is present it goes to LOW from time to time, which might give the
  * impression no motion is present. This program deals with this issue by
  * ignoring LOW-phases shorter than a given time, assuming continuous motion is
  * present during these phases.

 #include <LiquidCrystal.h>

 int calibrationTime = 10;   // seconds to calibrate PIR
 long unsigned int pause = 5000; // timeout before we "all" motion has ceased
 long unsigned int lowIn; // the time when the sensor outputs a low impulse

 boolean lockLow = true;
 boolean takeLowTime;

 int flashCnt = 4;  // number of times the LCD will flash when there's motion
 int flashDelay = 500; // number of ms to wait while flashing LCD
 int pirPin = 7;    // the digital pin connected to the PIR sensor's output
 int lcdPin = 13;   // pin connected to LCD
 LiquidCrystal lcd(12, 11, 10, 5, 4, 3, 2);

 void setup() {
     // Calibrates the PIR

     pinMode(pirPin, INPUT);
     pinMode(lcdPin, OUTPUT);

     digitalWrite(pirPin, LOW);


     // give the sensor some time to calibrate

     for(int i = 0; i < calibrationTime; i++){


 void clearLcd() {
     // Clears the LCD, turns off the backlight
     lcd.begin(20, 4);
     digitalWrite(lcdPin, LOW);

 void alertLcd() {
     // Turns on the LCD backlight and notifies user of motion
     lcd.setCursor(2, 1);
     digitalWrite(lcdPin, HIGH);
     lcd.print("INTRUDER ALERT!!");
     lcd.setCursor(2, 2);

 void loop() {
     // Main execution loop

     if(digitalRead(pirPin) == HIGH) {
         // flash an alert a few times
         for (int c = 0; c < flashCnt; c++) {

         if(lockLow) {
             // makes sure we wait for a transition to LOW before any further
             // output is made:
             lockLow = false;
         takeLowTime = true;

     if (digitalRead(pirPin) == LOW) {

         if (takeLowTime) {
             // save the time of the transition from high to LOW
             // make sure this is only done at the start of a LOW phase
             lowIn = millis();
             takeLowTime = false;

         // if the sensor is low for more than the given pause,
         // we assume that no more motion is going to happen
         if (!lockLow && millis() - lowIn > pause) {
             // makes sure this block of code is only executed again after
             // a new motion sequence has been detected
             lockLow = true;

My Fedora 11 Adventures: Part VI

Folks, I cannot take this any longer. I've had Fedora 11 installed on my computer for 5 days now. That is close enough to a week for me. There simply is not enough about Fedora right now to keep me using it. Perhaps the next release will be better for me. I honestly hope so.

To be perfectly honest, I enjoyed most of the Fedora experience these past few days. I was thoroughly impressed with the speed and memory usage in Fedora compared to Jaunty. When I mentioned that on Twitter the other day, one fellow asked if the two systems were running the exact same software. His train of thought seemed to be that you can't really compare two different distros for speed or memory usage unless they run the exact same software at the time of the sample.

My response to that is that it doesn't matter to me in this particular case. I was comparing the general performance of both distros using their "stock" configuration. You can customize a distro however you'd like, and, in the end, that's where you'll probably find the most performance gains in any system.

But performance out of the box is important to me. I'll just leave it at that.

As I write this, I'm creating an ISO of slackware-current (as of midnight MST) so I can see what KDE 4 is like on a real distribution. Heh. This oughta be fun. Anyway, I truly hope that the next release of Fedora will hold my attention for a bit longer.

My Fedora 11 Adventures: Part I

Today I decided that I would deliberately put myself outside of my comfort zone. No, not by intentionally putting myself on a telephone for more than 5 minutes this month... I will need a lot more preparation before I can attempt that one. No no, today's experiment has to do with Linux. If you're new around here, I am a very big fan of Linux. It has been my primary operating system for over 8 years (but I still use Windows and Mac occasionally, when I need to test my programs and the cross-platform behavior).

A Little Background On Yours Truly

There was a time when I was what you would call a distro-hopper. I would download any and every Linux distribution I could get my hands on. Most of them would hang around on my computer for a few days at best, but a select few actually impressed me enough to have them stick around for longer. Among those few are Slackware and Sidux. Many other distros are nice and pretty, but when it comes to me being productive on them, there always seems to be something lacking.

I am addicted to speed and reliability--two things that originally urged me to tinker with Linux all those years ago. I am more than willing to sacrifice looks and features for being able to just get something done quickly and efficiently. As a matter of fact, I'm writing this article in VIM, one of the most "light-weight" editors around these days. It allows me to do exactly what I want to do without getting in my way. That's how I like things.

That's probably the main reason I love Slackware. It won't do anything I don't tell it to do. No crazy background processes updating some package repository, slowing down my system. No pestering me about security updates that I will install in my own due time. Slackware only does what I want it to, and I have learned a ton about Linux because of it. If I decide I want something automated in the background, I have to tell the computer to do it. If one of my programs has been updated on the Internet, I download and install the package manually instead of using a "package manager." If one of my programs doesn't work because of a missing dependency, I am the one who finds and downloads the dependency. It's a lot of work initially, but I'm of the persuasion that this work is well worth it for my situation.

In today's day and age, that sort of setup seems to scare a lot of people off. People like to have things "just work." People like to not have to worry about keeping up to speed with what security threats are out there. People like having things to keep them entertained instead of getting things done. People like to see their desktop turn into a cube and spin around. People like to see things glow and wiggle on their computer. It's aesthetically pleasing. There's nothing wrong with that. Unless you want to get things done instead of just stare at your computer.

The Challenge

With that background in mind, you should be equipped to better understand the information and articles that follow. My challenge to myself is this: install Fedora 11 and use it for at least a week. To add to the the challenge, I'm installing the 64-bit version. In my past experience with 64-bit operating systems, there has been no real motivation or necessity for 64-bit computing. It just means more compatibility problems, which reduces productivity. This will be the first 64-bit operating system I actually plan to keep around beyond the exploratory period.

There are a few things about this that will bring me waaaay out of my comfort zone. They are (in no particular order):

  • Fedora
  • RPMs
  • KDE 4

I have a strong disregard for each of these items. There was a time when I considered Fedora to be a respectable platform--back when it was Fedora Core 2 or 3. Ever since then, I feel that it has gone down the tubes. RPMs have always seemed grossly lacking in the speed department to me, and it only got worse after I found out about Debian and Slackware. Finally, KDE 4 seems like one of the absolute worst window managers I have yet to encounter. I love KDE 3.5.x. I wish I could use it everywhere I go. But KDE 4 has yet to appeal to my desire for efficient productivity--it gets in my way almost as much as GNOME does.

Starting today, I plan to look all of these opinions (as biased as they may be) straight in the eye and take 'em head-on. I am going to work on learning to enjoy using Fedora. I'm going to work on learning how to appreciate RPMs. I am going to learn to be productive in the window manager "of the future."

And I will keep you all apprised of my progress.

Windows 7 Public Beta Screenshots

Here are some screenshots of the Windows 7 public beta. I installed it in a VirtualBox virtual machine and allocated 600MB of RAM to it.

The new and improved sloading screen

The new and improved sloading screen.

The login screen

The login screen

Logging in....

Logging in....

The desktop.... and a fish!!

The desktop.... and a fish!!

Your choices of Microsoft-sponsored security--the ones that will slow down your computer the most

Your choices of Microsoft-sponsored security--the ones that will slow down your computer the most!

Oh oh!!  It's Internet Explorer 8!  Chews up my site like a charm.

Oh oh!! It's Internet Explorer 8! Chews up my site like a charm.

Captionless taskbar icons until you hover.

Captionless taskbar icons until you hover.

The new Windows Media Player

The new Windows Media Player.

It's version 12!

It's version 12!

Setting your desktop theme

Setting your desktop theme.

Minesweeper wants hardware accelerated graphics

Minesweeper wants hardware accelerated graphics.... why??

All-new Minesweeper

The all-new Minesweeper.

I won!

I won!


Paint. Very perty.

The start menu

The start menu.

All programs in the start menu

Looking at all programs in the start menu.

Gadgets and the clock thingy

Some desktop gadgets and the clock thingy.


Slashdot in IE 8.


Downloading Google Chrome.

WTF?  Verifying application requirements??

What the....? Verifying application requirements??

Ahh... Chrome.

Ahh... Chrome.

Control Panel--stupid people's version

Control Panel--stupid people's version

Control Panel--all options

Control Panel--all options

Administrative tools

Administrative tools

Some things never change... but what's up with the 200MB partition??

Some things never change... but what's up with the 200MB partition??

First UAC popup...

First UAC popup...

Second UAC popup...

Second UAC popup...

Installing Avast

Installing Avast Antivirus.

Windows services

Windows services.... there are a ton of these as usual.

Pong Service for Wireless USB??

Pong Service for Wireless USB??

Heh... Preliminary scan results show that malicious or potentially unwanted software might exist...

Heh... Preliminary scan results show that malicious or potentially unwanted software might exist...

Oh, nevermind... we're good.

Oh, nevermind... Windows says we're good now.

Shutting down... took long enough to get a delayed screenshot.

Shutting down... took long enough to get a delayed screenshot. Could have probably shot 20 more.

Stage 1 of the sloading screen

Stage 1 of the sloading screen.

Stage 2 of the sloading screen

Stage 2 of the sloading screen.

Avast has started its scan

Avast has started its scan.

1% complete... after a few minutes!!

1% complete... after a few minutes!!

Done! after about 30 minutes...

Done! after about 30 minutes...

Third UAC popup...

Third UAC popup...

Trusted publishers?

Trusted publishers? These two screens kept coming up each time I would try to update Avast's antivirus database...

The Resource Monitor.  I was doing nothing at the time.

The Resource Monitor. I was doing nothing at the time.

Activating my copy of Winders 7

Activating my copy of Winders 7

w00t.  I'm legit.

w00t. I'm legit.

Benchmarking my system.

Benchmarking my system.

My VM ranks in at a solid 1.0!

My VM ranks in at a solid 1.0!

Details, details...

Details, details...

The classic Windows theme and a buffalo butt

The classic Windows theme and a buffalo butt...

Why all the games??

Why all the games?? Why not include something a little more productive??

Windows 7: First Impressions

I only have a minute or two to post a couple of thoughts about Windows 7. More to come later.

First, it installed a lot faster than I had expected, which was nice.

Second, minesweeper requests hardware accelerated graphics. MINESWEEPER!!!!!

Go Microsoft. Way to soup up the most retarded game of all time.

openSUSE 11.0: Round 2

Ok, ok... I decided to give openSUSE 11.0 another shot. Since my last blog post, I have read some reviews posted by some other people who encountered similar problems when attempting to actually use KDE4. Some of these people opted to install the KDE 3.5.9 remix after that and had more promising result. So, instead of letting my bias get the best of me, I am going to try openSUSE 11.0 one more time using KDE3. The following are the steps I took while going through this process:

  1. Booted from DVD (openSUSE 11.0 x86_64)

  2. Chose "Installation" from the boot menu

  3. After the installer is completely loaded, I selected "English (US)" for both the language and the keyboard layout, read the license agreement, checked the "I Agree to the License Terms" box, and clicked Next.

  4. I waited for a few seconds while the installer probed my hardware and updated some package lists, then I chose "New Installation" and clicked Next.

  5. The next step was to choose my timezone. They have a very simple interface for this--much less frustrating than the counterpart in the most recent release of Ubuntu (8.04 LTS). My system clock is set to Mountain time, so I left that stuff alone and clicked Next.

  6. This step is probably where I screwed up the most last time. It's where you choose which desktop environment you want. You can choose from GNOME 2.22, KDE 4.0, KDE 3.5, and XFCE Deskop. Last time I chose KDE 4.0. This time I chose KDE 3.5 and clicked Next.

  7. After choosing the desktop environment, the installer took me to the disk partition section of the installation. This should be pretty easy for most people, but I changed a few things. Namely, I put the root and home partitions together, and I deleted one of my Windows partitions because Windows is stupid and bloated. Once I verified the disk partition settings, I clicked Next.

  8. This part is where you get to enter the primary system user's information. You can specify the user's name, login, and password. You may also specify a few options including whether or not the root user will have the same password, whether that user will receive system mail, and whether or not that user will be logged in automatically. If you need to, you may change the authentication settings here too. I just entered the information and got on with it. (If you uncheck the box for the root user having the same password, you're prompted for the root password after this screen)

  9. Finally, we get to the step where you get to verify all of the installation settings. I think I'll just go with the configuration for now. When you click Install, you're prompted to verify that you really want to install. Use your head on this one.

  10. After all of that, it began to format my partitions. One neat thing that I noticed while it was installing was the fact that they rolled commonly-installed packages into what they call "images." This seems to increase installation speed considerably. In the past, I've had most RPM-based distribution installations take as long as (or longer than) Windows takes to install. Granted, the difference there is that you actually get useful stuff once Linux is installed, whereas with Windows, you're stuck with something barely usable and you still have to install drivers for every piece of hardware except your monitor.

    Anyway... the openSUSE folks seem to have addressed that problem recently (maybe just in this release). This went a LOT faster than I've ever seen (on any computer). Despite the use of those images, though, there were still nearly 500 packages that needed to be installed. It seems to be quite evident that the packages are working faster than ever before. It's refreshing (though it did still take quite a bit longer to install than most Debian-based distributions I've tried).

  11. After all of the packages are installed, the system does some configuration and then reboots itself. When it comes back up, the installer will appear, do some more hardware detection and configuration, and then go straight into your desktop.

openSUSE actually didn't detect my 1680x1050 resolution (I didn't know any modern distribution wouldn't anymore), so I just went into YaST and set the resolution to what it should be. And then it locked up, and I had to do a hard reboot. Let's hope I can stop that from happening again. I suppose so long as I can still see things other than my mouse, I should be good.

Upon rebooting into my desktop, the resolution was still crappy. When I went to change it this time, though, I noticed that dual-head mode was enabled. That's stupid. I never plug a second monitor into my laptop. I disabled that, then tried to change the resolution. After logging out and back in, it seems to have changed the resolution properly. While I realize that I do have an extremely crappy video card, Ubuntu and others have been able to offer me 3D acceleration. This option is currently unavailable with openSUSE. Perhaps a little research will solve that problem.

After a few minutes of configuration and preference setting, my system locked up yet again. And another hard reset did the trick of getting it operational again. One more and it's outta here!! I do have to say... Minus the quirks with the resolution and drivers, the distribution does not seem bad at all. It might be worth trying out on a different computer--maybe I'd have better luck.

Alright, now I'm going to check the software management tool for a real driver for my video card. Looks like I may have found some. I hope they work. I'm using a "1-click installer" that I found from a Google search. The installation went fine, but after logging out and back in (to have the drivers take effect), it locked up again.

So, round two folks. Again, it might just be user error. It might just be my computer. Or openSUSE really might just suck. I don't think I'll be trying it on my computer again for a while. I might try on a different system altogether, but not on my main laptop.

Windows XP: command != cmd

So I was trying to help one of my good friends get started with Django today. He managed to get Python and the development version of Django installed, but once he tried to actually start working on a project he ran into some strange problems. In the command prompt, he changed to the directory where he wanted to create his Django projects and tried to run the appropriate command to actually create one. It came back telling him it was and invalid command and all that. We checked the paths and whatnot, and everything seemed perfectly fine.

After a little bit of further tinkering, we agreed to let me use LogMeIn to try to figure out what the problem was. When I got into his computer, he had his command prompt open. Everything was a bit fishy--no tab-completion, 8-character file and directory names, all upper-case names, etc. At first I just assumed that he was using an older version of Windows XP. I was personally not aware that XP shipped with such outdated capabilities, so it was a big surprise for me.

Eventually, I decided to open another command prompt, and I noticed that the file names were all long and properly-cased. Tab completion also worked. Turns out that my buddy opened the command prompt using Start > Run: command.com, while I used cmd.exe. Strange that the legacy command prompt is still included in XP.

So if anyone else runs into similar problems, check which method you're using to open the command prompt.