Toys + Me = Fun

2010-11-22T19:10:00.001-08:00

POV on Netduino Mini

I'm working toward a POV-based game using the Netduino Mini. The video above is work in progress towards the game. It's just a basic POV (Persistence of Vision) that can be done just as well with any other Netduino, but it was a good project to get myself comfortable with the new Mini.

I use an FTDI breakout board to deploy the app from Visual Studio to the Netduino Mini, but you can also use real RS-232 via pins 1-3.

I've posted the full source code in Netduino Community, but here is the gist of it.

 foreach (char chr in message.ToUpper())  
 {  
   int alphabetIndex = (byte)chr - (byte)'0';  
   if (alphabetIndex < 0) alphabetIndex = Alphabet.alphabets.Length - 1; // Turn bad chars into space (last item in alphabet array)  
   for (byte columnIndex = 0; columnIndex < 5; columnIndex++)  
   {  
     int row = 1;  
     for (byte rowIndex = 0; rowIndex < 8; rowIndex++)  
     {  
       leds[rowIndex].Write((Alphabet.alphabets[alphabetIndex].ColumnBits[columnIndex] & row) != 0);  
       row = row << 1;  
     }  
     Thread.Sleep(colWidth);  
   }  
   //-- gap between characters --  
   for (byte rowIndex = 0; rowIndex < 8; rowIndex++)  
   {  
     leds[rowIndex].Write(false);  
   }  
   Thread.Sleep(gapWidth);  
 }

Outermost loop walks through the message string to be displayed, one character at a time.
For each character we calculate its index in alphabets array. We display each character, one column at a time. For each column we turn the appropriate LED rows on/off. At this point all rows of LEDs are displaying the correct pattern for that column of that character, so we pause for five milliseconds to let the slow humans to see it. :-) Then we proceed to the next column, next column, etc. Finally, we create a gap between characters by turning off all LED rows for 10 milliseconds.

In the full source you can see that we repeat the above code but in the reverse order. This allows us to display the pattern from left to right when the LEDs are swung in that direction, and display the characters and columns in the opposite direction when the LEDs are swung from right to left.

The piezo is beeped at the end of each cycle to hint the human of the rate that he should swing the LEDs.

It was an easy, quick, fun build. Off to the next project! :-)

2010-11-20T13:45:00.001-08:00

Netduino Mini Unboxing
Specs says how small the NetDuino Mini is, but seeing it in person next to the classic Netduino is still an impressive sight.
Two power regulators, an RS-232 level converter, and sixteen I/O in such as tiny package.
What will SecretLabs come up with next....

2010-11-14T11:34:00.000-08:00

Playing with VoiceBox Shield
Code is available on Fezzer.com

2010-11-09T22:26:00.000-08:00

Playing with Stepper Motor
I ordered a $5 stepper motor from emartee.com a few weeks ago. It finally arrived from Hongkong. EasyDriver from SparkFun really made it easy to drive this stepper motor. One pulse pin from the microcontroller can be used to rotate the motor. Another pin can be used if you want to also programmatically control the motor direction. You control the speed by varying the pulse frequency and/or changing the MS1 and MS2 pins (either manually or programmatically by connecting those pins to your microcontroller.)

Arduino + EasyDriver + Stepper Motor

Netduino + EasyDriver + Stepper Motor

Sample source code is attached to this Netduino forum post.

2010-10-31T23:07:00.000-07:00

Spider

First, the bad news... It can't walk :-(
Those $3 servos are too weak to support the weight of the spider, let alone lift up the body and walk. Even without the batteries, the weight of twelve servos are too much for those cheap servos.

However, I'm still very pleased with how much I was able to accomplish in just a few days. I wasn't going to enter the Halloween contest, but then I saw that there are only a few entries three days before the deadline, I decided to spend this weekend working on this spider.

First, I need some servos. Spiders have eight legs, I need two servos for each leg (one to lift the leg up and one to pivot the leg forward and backward). Grrrr, I do not have sixteen servos! I ran out of servos when I built Daft Punk Panda, so I ordered two new servos. Hey, that's twelve servos. Enough servos for six legs! Bye bye Pandas... :-(

Originally, I thought I could make the spider body pretty much the size of the FEZ Panda. Those mini servos are very small. However, the horizontal rotation requires more spacing between the servos, so the spider ended up a little larger than the plan below.

I realize that those mini servos are not very powerful, so I tried hard to limit the weight. Breadboards are heavy and bulky, so I made a poorman's shield out of a RadioShack perf board. It plugs into Panda's digital pins and the servos plug into it. Very compact, very light.

Originally, I thought I would need to supply 5V to those servos. I plan on wiring one up on a perf board, but before I did that, I lost a lot of time debugging a very disturbing bug. The legs would work individually, but they just froze up when I move many legs at once. After much anguish, I discovered that one 7805 just could not reliably supply enough current for all twelve servos. Wiring up a second 7805 fixed the issue. However, this morning, I bought a set of 15-minute rechargable batteries from RadioShack, and four of those AA batteries measure a little above 5V, the servos aren't that picky, so I connected the AA batteries directly to the servos. Worked great!

I already have some thoughts on improving the design (even without new servos), so this is probably not the last time you'd see this spider.

2010-10-21T17:43:00.001-07:00

Daft Punk Pandas
After much hard work, my mystery project is finally ready. :-)
Daft Punk's Harder, Better, Faster, Stronger performed by robot Pandas! Enjoy...

Behind the scene is a FEZ Panda microcontroller from TinyCLR.com driving TEN mini servos!
I think it's amazing that the FEZ Panda can drive ten servos without the aid of a servo controller. I wired up a 5V power supply to power those servos, but all 10 signal pins are directly connected to FEZ Panda's digital pins. No chips, no transistors.

Most of the hardware you see in the photo are unused. They're just there from previous projects. The slider switch marked P / Rec is of note however. Rather than trying to program the servos to move in sync with the music, I decided that it would be easiest to record the performance instead. I hardcoded an array containing the words of the song. I would press the pushbutton at the feet of the pandas to reveal the words. When I slide the switch to P, pressing the same pushbutton would playback the words at the correct times.

Another non obvious thing I did was to play the original soundtrack at 0.5x speed and record those times at that speed and then at playback the FEZ Panda multiplies the times and plays them back at 2x speed. The recording process took longer, but resulted in much more accurate syncing because slight misses I made during the recording were diminished during playback.

I thought it would be interesting to see a project evolve, so I took videos at various points of the project.

(more to come...)

2010-10-11T18:53:00.000-07:00

FEZ Domino USB Morse Keyboard
Another Freakin' EZ project. I took Scott Hanselman's morse app that he wrote for the Netduino and added a keyboard and beeper. Very useful if I ever have to communicate with a ham radio operator who only understands morse code. :-)

Full source code available here

2010-10-10T23:09:00.000-07:00

FEZ Domino Wireless Mouse Demo

Although originally I wrote a lot of code to do this. However, in the end, I only had to write about 10 lines of code to accomplish this cool demo! The rest of the code came from the USB Host mouse demo and the ServoMotor class.

Here is the heart of the code. :-) Can't get easier than this!

 static void MouseMove(USBH_Mouse sender, USBH_MouseEventArgs args)  
 {  
   servoX.Angle = (byte)(180 - (sender.Cursor.X / 4));  
   servoY.Angle = (byte)(sender.Cursor.Y / 4);  
 }

The divide by four is to make the mouse less sensitive.

Originally, I wrote my own Servo class, but later discovered that GHI's ServoMotor (uses OutputCompare) worked better than my PWM based class. See sample usage here.

Using USB Mouse is discussed on page 109 of Beginners Guide to C# and .NET Micro Framework

Full solution available at http://www.microframeworkprojects.com

2010-10-09T17:16:00.000-07:00

KeyRace - FEZ Domino USB Host Demo

Unlike most FEZ / Netduino / Arduino, the FEZ Domino supports USB host which means not only it can act like a keyboard, but you can plug a keyboard into a FEZ Domino and use it within your NETMF applications. Very powerful.

KeyRace is an app I create to practice using this USB host feature. It also includes a class library for Scott Edwards Electronics' BPI-216 Serial LCD and a class for Piezo speaker sound effects.

It displays words from a resource, you're supposed to re-type them (more time is allowed for longer words). If you correctly re-type the word, you get a point, if you miss it you loose a point. If point goes negative, you loose. If you made it all the way to the word list, you win.

The word list is easily modified, it's in a resource. The difficulty level is also easily configured.

Download the code here: http://www.microframeworkprojects.com/index.php?title=KeyRace

2010-10-02T12:58:00.000-07:00

Morse Code Decoder
When I saw this post, I thought it would be cool to write an app that goes the opposite direction. Instead of blinking out morse code, the app would "look" at the morse code, measure the pulse and pause widths and convert them back into words.

Looking at the blinking LED was easy, but converting that back into morse code was more difficult than I expected.

If you're interested in building this, as long as you have two Netduinos (they're hard to find these days), you can easily get the other parts from your local RadioShack:

Two Netduinos (or Netduino Plus)
Any Light Dependent Resistor (LDR). I use RadioShack Part 276-1657 Cadmium-Sulfide Photocells
1K resistor
10K Linear Potentiometer
Breadboard & Jumper wires
Optional Serial LCD (mine requires the serial signal to be inverted, hence the SN7404 Hex Inverter)

The RadioShack pack contains five LDR of varying size and resistance. I measured them in similar lighting condition and picked the one with least resistance. For those unfamiliar with LDR, their resistance lowers when you subject them to more light. By wiring them as a resistive voltage divider, resistance of LDR (R1) would decrease as we subject the LDR to more light causing voltage at Vout to rise. Very intuitive. Light On = High(er), Light off = Low(er).

I mimicked this voltage divider with the potentiometer, wiring one to ground, the other to Vcc, and measuring the middle wiper. I feed the Vout of the LDR voltage divider, and the potentiometer into Netduino's Analog inputs. Comparing the two values really saves time, otherwise I would have to adjust the sensitivity by changing constants in code.When digitized value of Analog0 is higher than the threshold set by Analog1, then I turn on the LED as feedback that the sensitivity setting is correct.

If you'd like to challenge yourself into writing the code, you should quit reading now. I'm about to talk about the code. :-)
At this point, I thought it would be just a matter of measuring how long the light is on (I call this "pulse"), and how long the light is off (I call this "gap"), and converting that into dits and dahs, and then back to text.
The other last two steps were easy, but measuring the time prove to be more difficult. There is no such thing as an Analog InterruptPort, so I had to do this manually. My first try did not work, but the second try (below) worked great.

 public void Listen()  
 {  
   DateTime now = DateTime.Now;  
   bool isOn = IsOn();  
   //                               __     
   //-- Rising from low to high __/    
   if (!wasOn && isOn)  
   {  
     long gapWidth = (now.Ticks - lastFall.Ticks) / TimeSpan.TicksPerMillisecond;  
     lastRise = now;  
     PrintGap(gapWidth);  
   }  
   //                           __  
   //-- Falling from High to Low  \__   
   if (wasOn && !isOn)  
   {  
     long pulseWidth = (now.Ticks - lastRise.Ticks) / TimeSpan.TicksPerMillisecond;  
     lastFall = now;  
     PrintPulse(pulseWidth);  
   }  
   wasOn = isOn;  
   //Debug.Print(gapWidth.ToString() + " " + pulseWidth.ToString());  
 }

This Listen() method is called repeatedly by Main(). First we get current time (not really actual time in real world, but everything is measured relatively so it doesn't matter what time it really is). IsOn() handles the threshold we talked about earlier, we conveniently gets a true if light is on, false if light is off.

The two if statements detect whether we are transitioning from low to high or vice versa. If we're on the rising edge, we compute how long was the previous gap (how long was the last low) by subtracting the last time there was a falling transition from current time. We had to divide it by Ticks per millisecond because we will compare this against constants that are in milliseconds. Then we memorize this rise/fall time and call PrintGap/PrintPulse who will print the morse/gap and convert it back to a letter.

Finally we update wasOn, for the next time we're called by Main().
Once we have the length of the gap and pulse, it is fairly straightforward to convert it back into dits and dahs.

 //-- Translate pulse width into dit or dah --  
 private void PrintPulse(long pulseWidth)  
 {  
   string symbol = "";  
   if (pulseWidth > dittime * 2)  
     symbol = "-";  
   else  
     symbol = ".";  
   morseCharacter += symbol;  
 }

When we see a gap wider than the gaps between dits and dahs, we know it's the start of a new character or word, so we call MorseToChar() to convert the collected dits and dahs back into a letter.

 private char MorseToChar(string morseStr)  
 {  
   char letter = ' ';  
   for (int i = 0; i < MorseCode.Length; i++)  
   {  
     if (MorseCode[i] == morseStr)  
     {  
       letter = Letters[i];  
       break;  
     }  
   }  
   return letter;  
 }

Full source code is attached to this post.
The source for the Morse Code sender written by N2MOH can be found here.

I'd be happy to respond to questions, comments and suggestions.
Have fun!

2010-09-25T10:19:00.000-07:00

Netduino IR Distance Sensor
Just playing around with the Sharp GP2Y0A21YK IR Proximity sensor and getting re-aquainted with my antique 2x16 Serial LCD Module (it doesn't even have a backlight and require inverted TTL input - hence the SN7404 hex inverter).

Below is a snippet of the full code that is available here.

 public class Program  
 {  
   static SerialPortHelper serialPortHelper = new SerialPortHelper();  
   static AnalogInput analogInput = new AnalogInput(Pins.GPIO_PIN_A0);  
   public static void Main()  
   {  
     serialPortHelper.PrintClear();  
     serialPortHelper.Print("IR Distance");  
     while (true)  
     {  
       Thread.Sleep(100); // Don't do anything for a bit to allow AnalogInput to gather sample  
       int analogValue = 1024 - analogInput.Read();  
       //-- Print value (useful to see analogValue range) --  
       serialPortHelper.MoveTo(0, 12);   
       serialPortHelper.Print(analogValue.ToString());  
       serialPortHelper.Print("  "); // Erases left-over digits from previous analogValue if it had more digits.  
       //-- Bar Graph --  
       serialPortHelper.MoveTo(1, 0);   
       serialPortHelper.PrintBarGraph(analogValue, 70,980);  
     }  
   }  
 }

2010-09-25T09:46:00.000-07:00

Netduino Tip 04: Foam Board Project Base

Have you noticed how electronic parts and wires seem to defy gravity? They do not tend to stay put on the table while you're working on your electronic project. Foam board to the rescue!
They're inexpensive ($12 for three 20"x30" boards, enough for many projects), easy to work with (box cutter, ruler, hot glue gun), and non-permanent (at worst you'd need to scrape off the glue residue after you tear off the foam, and the larger foam pieces can be reused). I've built many bases like this, enclosures for finished projects, and even a remote controlled robot.

2010-09-21T21:53:00.000-07:00

Netduino SerialPort Code

My next project involves Netduino's SerialPort. So I wrote this to make sure that I can reliably communicate via SerialPort. You can download the code here.

Demo of Netduino's SerialPort communication capability.

Second video explains the wiring and reviews the actual code.

2010-09-19T09:25:00.000-07:00

Netduino Ringtone Player
A snippet of code to play a tone on the Netduino forum inspired me to create this.
It was a lot of fun to write. Code is attached on this post.

2010-09-17T22:34:00.000-07:00

Arduino Data WebServer
Sample Web Server running on the Arduino + Ethernet Shield.
Depending on the url used the Arduino will do something and/or send something back. The code is intentionally simple so you can modify it for your own Ethernet Shield projects. Enjoy!

I have an NKC Ethernet shield, but I'm using the standard Arduino Ethernet library, so it should work with the Arduino Ethernet Shield too.

Part 1: Demo (shown above)
Part 2: Code Explained
Part 3: Code Explained continued

Code is available in the Arduino Forum.

2010-09-14T22:41:00.000-07:00

Netduino Tip 03: Servo

This is more of a reference than a tip. You can see above the two common servo cable colors and what they mean. Plus should be connected to an external 5V source with common ground, but it seems to work ok off the Netduino 5V for this experiment. Finally, signal wire should be connected to one of the four PWM digital pins (5,6,9, and 10). In the code, just specify which PWM pin to use when you instantiate the Servo class, then set its Angle property. That's all there's to it.

Program.cs

 using System.Threading;  
 using SecretLabs.NETMF.Hardware.Netduino;  
 using Microsoft.SPOT;  
   
 namespace SimpleServo02  
 {  
   public class Program  
   {  
     static Servo[] servos = new Servo[4];  
   
     public static void Main()  
     {  
       //Netduino only has four PWM pins: GPIO_PIN_D5, 6, 9, and 10  
       servos[0] = new Servo(Pins.GPIO_PIN_D5);  
       servos[1] = new Servo(Pins.GPIO_PIN_D6);  
       servos[2] = new Servo(Pins.GPIO_PIN_D9);  
       servos[3] = new Servo(Pins.GPIO_PIN_D10);  
   
       while (true)  
       {  
         MoveServos(0);  
         MoveServos(90);  
         MoveServos(180);  
       }  
     }  
   
     private static void MoveServos(uint angle)  
     {  
       for (int i = 0; i < servos.Length; i++)  
       {  
         servos[i].Angle = angle;  
       }  
       Thread.Sleep(2000);  
     }  
   }  
 }

Servo.cs

 using Microsoft.SPOT.Hardware;  
 using SecretLabs.NETMF.Hardware;  
   
 namespace SimpleServo02  
 {  
   public class Servo  
   {  
     PWM servo;  
   
     public Servo(Cpu.Pin pin)  
     {  
       servo = new PWM(pin);  
       servo.SetDutyCycle(dutyCycle: 0);  
     }  
   
     private uint _angle = 0;  
   
     public uint Angle  
     {  
       get  
       {  
         return _angle;  
       }  
   
       set  
       {  
         const uint degreeMin = 0;  
         const uint degreeMax = 180;  
         const uint durationMin = 500;  // 480  
         const uint durationMax = 2300;  // 2450  
         _angle = value;  
         if (_angle < degreeMin) _angle = degreeMin;  
         if (_angle > degreeMax) _angle = degreeMax;  
         uint dur = (_angle - degreeMin) * (durationMax - durationMin) / (degreeMax - degreeMin) + durationMin;  
         servo.SetPulse(period: 20000, duration: dur);  
       }  
     }  
   }  
 }

Setting SetDutyCycle to zero means output will be continously low.
The SetPulse method would send out a pulse of the proper width for the desired angle. You may need to adjust durationMin and durationMax for your particular servo.

2010-09-03T14:30:00.000-07:00

Netduino Tip 02: Aref and AnalogInput

Unlike the Arduino, the Netduino requires that you to supply a reference voltage before AnalogInput would work. If you forget to do this, AnalogInput would return the maximum value most of the time, with occasional spikes of random values.

Note the Aref pin on the top left of the Netduino is connected to +3.3V.
The three wires on bottom right of photo correspond to the left, middle, and right pins of a 10K potentiometer.

Here is the code:

Note that SetRange is optional, though very handy. It allows you to scale the default 0-1023 to whatever range is convenient for your use. The smaller the difference between the SetRange parameters, the less jitter you would get from one sample to the next.

2010-08-30T19:39:00.000-07:00

Netduino Tip 01: Zzz

See if you can spot my mistake.

Timers and Interrupts do not block Main() thread. As soon as Netduino hits end of Main() everything stops! Although the Timer is setup correctly, Main() immediately quits and the timerCallback will never be called. The fix is easy. Tell Netduino to sleep forever while we wait for Timer to fire every 1000 milisecond.

2010-08-30T17:37:00.000-07:00

My Netduino is here!

This white box is inside an Amazon box.

Inside is the pretty blue Netduino box.

Unlike Arduino, Netduino arrives with a USB Cable.

For some reason, I expected it to be bigger.

Secret Labs is generous in including the USB cable and also rubber feet.The coloful piece of paper is a Microsoft Tag. When I scanned it using my Android phone, it shows me Netduino's home page. Cool, but Secret Labs probably should just include a piece of paper welcoming me to the Netduino world.

I've written a few small test apps, so far I think it's a cool $35 toy.

2010-08-27T22:41:00.000-07:00

Arduino, Netduino, Fez Panda compared

I gather this info from the three sites linked in the table below.I found three Arduino form-factor boards. Well, actually four if you count the Fez Domino, but its $75 price puts it out of my consideration. The Fez Panda is supposed to ship on Sept 15, 2010.
Please post a comment if you see anything that I need to correct. Thanks!

	Arduino Duemilanove	Netduino	Fez Panda
Price	$30	$35	$35 $20 sale
Processor	16Mhz ATmega328	48Mhz AT91SAM7X512	72Mhz 32-bit ARM
User Flash	30KB	128KB	148KB
User RAM	2KB	60KB	62KB
TCP/IP	Shield	Soon	Basic
I/O	14	14	60
PWM	6	4	6
Analog In	6	6	8
Analog Out	0	0	1
UART (serial Ports)	1 TTL	2 TTL	4 TTL
SPI	1	1	2
I2C	Yes	Yes	Yes
CAN	?	?	2
1-wire	Yes	?	Yes
USB Host	No	No	No
USB Client	No	Yes	Yes
Assembled	Yes	Yes	Yes
100% Open Source	Yes	Yes	Yes

2010-08-21T20:42:00.000-07:00

Lifelike Netduino Emulator
I played around with Netduino Board Emulator by onir while waiting for my actual hardware to arrive.

2010-08-21T07:53:00.000-07:00

Shoot first, ask questions later

I've been thinking about getting a FEZ, but the cheapest model available is $50, almost twice as expensive as the Arduino. Yesterday, I found out about the NetDuino (thanks Steve!) It is similar to both FEZ (programmable in .NET) and Arduino (physically and pin compatible with Arduino expansion shields), and it is only $35 including shipping from Amazon!

I was going to research availability of networking stack on NetDuino, but was too excited to wait, so I decided to shoot my order first and asked questions in the forums later :-) By following the getting started PDF from the NetDuino site, I've been able to play with the IDE (Visual Studio Express) and run/debug code on the built-in emulator before I even received the NetDuino hardware! Here's the simplest program I can think of:

For those unfamiliar with .NET, everything (classes, methods, constants, etc) exists within a particular namespace. For example, Microsoft.SPOT namespace contains the Debug class that contains the Print method.

You can avoid typing the namespace Microsoft.SPOT all the time by including a using statement.

2010-03-28T22:40:00.000-07:00

Programmable MIDI drumkit

*** WARNING ***I didn't have any zener diodes on hand to limit the Piezo output and lived dangerously. I cannot be held responsible if you kill your Arduino! See Todbot's Spooky Arduino below for more info.

I don't have any aspirations to be a drummer, but I'm interested in interfacing the Arduino to MIDI, so I got a MIDI jack from DigiKey and a couple Piezo Transducers from Radioshack and built this drumkit.

I learned how to do this from these pages:

You can get the Sketch/Code here.

2010-03-24T23:16:00.001-07:00

Workspace, originally uploaded by hwiguna.

This is my actual "work" bench, where I work as a software developer.
During the day Arduino stuff lives in plastic drawers underneath the table. At night... Arduino comes up and play. :-)

Click photo to go to Flickr and mouse over to see descriptions.

2010-03-13T15:32:00.000-08:00

Making my own Arduino USB cable

I don't know how these people in HongKong can sell USB data cables for Nokia phones for only $2.68! with FREE SHIPPING! One caveat, at $2.68, you must be patient. Mine took 17 days to arrive to USA. :-(

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=320481013758

I followed most of the instructions on Jonathan Thomson's weblog and successfully made my own Arduino cable.

A bit of solder, heatshrink tubing, and hotglue. There I fixed it! ;-)

I didn't read his blog carefully enough prior to ordering the cable, and learned a few things as I built my cable.

1. The basic mod (without adding an external wire and doing extensive surgery) would NOT automatically reset the Arduino. To upload a new sketch to the Arduino, you have to hold the reset switch, press Control-U to upload, and release the reset switch when the compile is done (bottom of Arduino IDE displays how many bytes the compiled code is). Despite the warning on Jonathan's blog, upload works all the time for me. I have not decided if having to press the reset button is worth the money savings or not. :-)

2. The USB to serial chip in the cable is not the usual FTDI, so it requires a different driver installation. Thankfully the cable came with a driver CD. Installed on Vista with no problems.

SparkFun $14 FTDI breakout vs. DYI $3 cable

One cool thing about having two USB to serial cables is that I was able to run two Arduino IDEs, set them to two different COM ports and work on both my Transmitter and Receiver Arduinos without having to plug/unplug anything. Not bad for $3 and a bit of soldering. Thanks Jonathan!

2010-03-12T23:17:00.000-08:00

M.I. Aiga - my first robot
It's not much to look at, ok, ok, it's ugly :-) It was a fun and educational project though. I learned about H-Bridge and got a chance to use WiiChuck adapter and the RF Link.

Goal
To wirelessly control a moving platform with a Wii nunchuck using one Arduino as a transmitter and another as a receiver.

Phase 1
Originally I plan on using discrete transistors to drive the DC motors, but I discovered that using an H-Bridge chip is a lot simpler and cost about the same. So while I waited for the chip to arrive, I hooked up six LEDs to represent the control lines of the SN754410 Quad H-Bridge chip. Three LEDs for each motor represents Enable, Clockwise, and CounterClockwise. This was a blessing in disguise, debugging the code using LEDs was much easier to visualize and quieter too.

Phase 2
H-Bridge chip installed with no problems! Unless your motor needs more power than these chips can handle, I can attest that using a chip is a lot easier than wiring eight Darlington transistors!

Here M.I. Aiga is chasing the cats. I discovered that when both DC motors are running at full speed, the robot stopped responding. I solved this by adding a dedicated 9Volt battery for the Boarduino.

Interesting components
RF Link from SparkFun
The transmitter is $4, the receiver is $5. So for $9, I was able to make one Arduino send commands to another Arduino wirelessly using Mike McCauleys VirtualWire library. It is only one way, but hey, it's less than ten bucks!

WiiChuck adapter from FunGizmos
There are no electronics on this adapter, but it allows you to hook up a Wii Nunchuck without altering it in any way. $4 may seem kinda steep for a tiny piece of PCB, but that includes shipping.

Gearbox with two DC motors from SparkFun
I'm pleased with this $11 gearbox kit. It came with two DC motors that fit into one gearbox, but each motor and its associated gears can move independently of each other. You may have noticed how loud they are in the video, this is due to the foamboard construction that I use. I don't remember it being that loud before I mounted the gearbox on the "chasis".

SN754410 Quad Half H-Bridge from ebay (DigiKey didn't have any in stock)

This thing is amazing. It contains four half H-bridges, so I used two for the left motor, and two for the right. Pin 1 enables/disables left motor. I use PWM on this pin to control the speed of that motor. Pins 2 and 7 (labelled 1A and 2A) are also hooked up to the Arduino, and they control the direction of the motor. Finally, pin 3 and 6 (labelled 1Y and 2Y) are hooked up to the motor. Repeat same circuit for the other motor.

The Spoon
One of my favorite part of the robot is the plastic spoon that I use as a caster. I got the idea from here. It works very well on carpet and linoleum. Cost? Priceless! :-)

2010-03-04T22:56:00.000-08:00

H-Bridge experiment

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1267678181

2010-02-28T22:10:00.000-08:00

Arduino related parts

TLC5940 - 16 Channel LED Driver with Dot Correction & Grayscale PWM Control
Examples: 112 RGB LED Coffee Table

TPIC6C595 - Power Logic 8-bit shift register
Examples: 56x8 scrolling LED matrix

TC74HC595 - 8-Bit Shift RegisterLatch (3-state)
Examples: Arduino ShiftOut

TIP102 & TIP107 - Complementary Darlington Transistors
Examples: Selecting the right H-Bridge Transistors
Buy: Digikey

TIP120 - NPN Epitaxial Darlington Transistor
Examples: Control Speed & Direction of a DC motor
Buy: Digikey

L293 - Quadruple Half-H Drivers
Examples: DC Motor Control using an H-Bridge

SN754410 - Quadruple Half-H Drivers
Examples: DC Motor Control using an H-Bridge, Dual Motor Driver
Buy: Digikey , SparkFun

MCP23016 - I/O Expander I2C
Examples: Arduino I2C Expansion I/O
Buy: DigiKey

SD-50J- MIDI Receptacle
Examples: MIDI Output using Arduino
Buy: DigiKey

RF Link Transmitter & Receiver (they have 315MHz, 434MHz at 2400 or 4800bps)
Example: VirtualWire Documentation, RF communication using VirtualWire
Buy: SparkFun

WiiChuck Adapter
Buy: FunGizmos

Gearbox with two DC motors
Example: M.I. Aiga
Buy: SparkFun

DS18S20 - 9-bit High-Precision 1-Wire Digital Thermometer $5

Part Stores
digikey.com

sparkfun.com

adafruit.com

fungizmos.com

http://www.goldmine-elec.com/
http://www.alltronics.com/
http://www.allelectronics.com/
http://www.bgmicro.com/

2010-02-28T12:42:00.000-08:00

Breadboard Customization
I asked the Arduino forum for suggestions on where to get a breadboard. They highly recommended a big Elenco board, but I really wanted separate boards, so I compromised and get four smaller Elenco boards.

When I got them, I was disappointed that the power bus lines are not detachable, so I cut the backing so I can separate the bus lines.

I now can rearrange the boards to best fit the project. For example, in this LED matrix project, I repurposed some of the power bus lines as 8 common anode row lines shared by all displays. Unfortunately, when interlocked in this configuration, the board has a slight upward curl. :-(

I made a "frame" out of foam board to corral the boards together, it works quite well. An unexpected benefit was being able to hold the whole project in one hand while orienting it in 3D to get the best viewing angle to insert a wire in a particularly crowded area of the board using my other hand.

I'm quite pleased my Elenco boards. For $6 each, they come with positive and negative bus on each side of the board. They are 65 holes wide vs. only 47 on the RadioShack. Furthermore, wires plugs in easier into the Elenco than the RadioShack. Thanks Arduino forum!!!

2010-02-28T03:08:00.001-08:00

Arduino 56x8 scrolling LED matrix

Seven TPIC6C595 to drive the 56 columns,
one 75HC595 to drive the 8 rows
on four Elenco breadboards

Powerlines

56 resistors

After several tries, I was able to fit seven 8x8 matrix side-by-side on a breadboard and not have wires crossing over the displays. The key is to put the chips on one side (rather than above or below) the matrices. You can put another 7 driver chips on the right side and double this to a fourteen 8x8 side-by-side matrix!!!

By customizing the breadboard, I was able to rearrange where the power buses are and use them not for power, but to have a common bus for the eight anode rows shared by all displays.

Code is available in the Arduino Forum. See the eleventh message of this thread.

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1267391793/7

2010-02-14T15:36:00.000-08:00

How to build your own pan/tilt bracket
Although you can buy pan/tilt brackets, I thought it would be fun to make one myself. So I did.

This is what we're building.

The material I use is inexpensive foam board that you can get from most office supply stores. I use a hot glue gun to glue everything together. As far as the electronics, you would need two servos (I got mine for $2.77 each at hobbypartz.com), an Arduino (I got mine from AdaFruit.com), and optionally a breadboard.

Using box cutters (no, you won't be able to build this on a plane), I the cut parts as shown in photo above. I use the servo itself to help me with the actual piece dimensions. The only thing you need to watch for is that there is enough clearance for the webcam to tilt back and forth.

The tilt section will pivot on the servo horn on one side and on the nail on the other side. While lining up the two side pieces, I press on the servo, leaving the indent of the servo axle so I would know where to put the nail through.

This is what is what the tilt servo looks like after I hot glue them together. Note how the nail nicely line up with the servo axle.

In this picture, the part we've been working on is shown upside-down. I've already screwed the horn on the servo and hotglue that side the piece where the webcam will rest on.

IMPORTANT: Make sure you manually rotate the servo axle back and forth to discover its 180 degree range and glue the webcam platform piece accordingly so pieces won't collide with each other as the servo moves through its full range.

Tada! The pan servo mount is simply three foam boards with the same hole cut in them to keep the servo in place. I used rubberbands to hold that base and wires onto a heavy box for stability.

See it in action here.

2010-02-14T13:48:00.000-08:00

SkyDuino - Webcam Pan/tilt via Skype

Using Skype API, I was able to remotely move my home webcam without running a webserver at my house. If you're interested in duplicating this, all source is available for free below. Post a comment if you have questions.

SkyDuino Windows v1.0.1 (At the remote location, you need this and Skype)
SkyDuino Sketch (You need to upload this to the Arduino)
SkyDuino Windows Source (if you're interested in the C# source code)
SkyDuino Fritzing Diagram (How to connect the Servos to the Arduino)
How to build your own pan/tilt bracket

2006-04-06T21:19:00.000-07:00

Wired News: Windows on Mac, Simultaneously
My geek wish had been granted.

2006-04-03T06:50:00.000-07:00

Uêba - Incredible Little Mech Sculpture

2006-03-04T19:12:00.000-08:00

A Mediation On The Speed Limit
You can agree or disagree with their method, but they made their point.

2006-03-04T09:56:00.000-08:00

Google GDrive
Sure, people trust GMail, but would they trust GDrive?
What if the government demands that Google hands out GDrive data?

2006-03-02T18:47:00.000-08:00

Spore Gameplay Video
Amongst the glut of shoot em ups, finally something completely new. You start playing as a tiny organism, growing up all the way to flying a UFO conquering galaxies! And everytime you "grow-up" you design your next creature self and habitat. Very impressive coding: everything is computed procedurally (walk cycles, behaviors).

2006-03-02T07:00:00.000-08:00

advAJAX / AdvancedAJAX 1.0
I wasn't even going to look at another AJAX framework, but glad I did. This code is so easy to read and it's FREE even for commercial use. Checkout the examples and source codes at the end of the page.

2006-02-27T20:37:00.000-08:00

Dave Werner's Portfolio 2006

2006-02-27T20:04:00.000-08:00

Emily Chang's eHub
Links to interesting web 2.0 related sites. Even more bloggers at web 2.0 workgroup

2006-02-19T20:44:00.000-08:00

Albino Blacksheep

Step-by-step visual tutorial on how to dress up a site with CSS.

2006-02-19T10:00:00.000-08:00

Articles at The Official Microsoft ASP.NET 2.0 Site
I'm not sure how I got here, but it appears to be a comprehensive list of articles available at the ASP.NET 2.0 site.

2006-02-18T21:58:00.000-08:00

Ask A Ninja
He's got some funny episodes before, his latest: "Ninja Dogs" (Tuesday, February 14, 2006) is going to be a classic. He's got bandwidth issues, so don't stream it, download it.

2006-02-16T21:30:00.000-08:00

Face Transformer
This creepy Java web app takes any face and apply various transformations: age, gender, race, and render styles (Anime, Botticelli)

2006-02-12T18:15:00.000-08:00

Transformer
Sony's Aibo and Qrio have been discontinued. So it's good to see that others are still passionate about small robots.

2006-02-08T22:02:00.000-08:00

Multi-Touch Display
Amazing video of multi touch detection using FTIR (frustrated total internal reflection) borrowed from fingerprint image acquisition.

2006-02-05T21:18:00.000-08:00

Microsoft Expression Tours & Demos
I've been ignoring Microsoft Expression, thinking that it's just another paint program but it's more than that. The Graphic Designer is the paint/draw part of Expression, but it also has an Interactive Designer to design GUIs, and a Web Designer. I heard they're going to release Microsoft Expression at Mix06.

2006-02-03T23:09:00.000-08:00

Different District
I don't know how they skirt around the copyright issues, but they claim to have 300 Apple related videos.

I don't watch much TV so I missed this hillarious SNL Steve Jobs parody.

2006-02-03T22:50:00.000-08:00

Typenow.net
Hundreds of FREE fonts used by movies and products.

2006-02-03T13:36:00.000-08:00

HTTPanties
403 Forbidden
411 Length Required
413 Requested Entity Too Large!!!

That's hillarious! LOL
Thanks Denise.

2006-02-03T06:31:00.000-08:00

MacMINI in SE30
Yes, he managed to put a MacMini inside an old Mac SE/30 case. The display works.

Someone should put a MacMini inside one of those zero footprint computers.

2006-01-21T19:38:00.000-08:00

Scott Hanselman's 2005 Ultimate Developer and Power Users Tool List
From Screen Capture to Unit Testing, Scott has gathered the best utilities in one place.

2006-01-21T19:03:00.000-08:00

Free Website Templates
No budget for a professional web designer? No problem.

2005-12-19T19:24:00.000-08:00

Visible Trace Route using Google Maps

2005-10-28T21:56:00.000-07:00

Sony's Bravia Ad

2005-10-13T20:29:00.000-07:00

Cardstacker FAQs

I bet that this guy doesn't drink coffee.
Amazing creations, check out his gallery.

2005-10-10T20:50:00.000-07:00

LogMeIn - Remote Access and Desktop Control Software for your PC