I’m still investigating different technologies in driving this project but it looks like I’ll be using 6 TLC59401 IC’s from Texas Instruments to generate the PWM signals and using the TL4242 as a constant current driver for each channel.  I plan on using a WiFly module for wireless communications at high speeds without the need for an xbee module to carry around with me. To interlink all of the communications and operate the TLC59401′s I will be using an AVR microcontroller from Atmel (since I already have the programmer and I am familiar with the chipset)

To be continued..

So, here they are in action for everyone in the world to see. Check out the full youtube page to see all of the juicy technical details. If this gets popular enough I’ll take some pictures but right now I’m way too lazy to get them off the wall and find a suitable camera. But for now, Enjoy!

1. The maximum “recommended” baud rate is 115200 baud.  The specifications says that the max baud rate is 250000, but that is for RF transmission. You can set nonstandard baud rates and even go higher than 115200 using the API or AT commands, but it could lead to corrupt data and lost packets.

2. Hardware “Flow Control” is a MUST. Always check the CTS (Cear to Send) line to see if the XBee is even ready to send a new packet. If you don’t, the Xbee’s send buffer will fill up quickly and packets will be lost.

3. You can actually use two different baud rates on both sides. Lets say you have a device (such as a USART camera) that communicates at 9600 baud. You can configure the Xbee to run at 9600bps , and send it to another Xbee that is configured to say 38400 baud. Sending to a device with a higher baud rate is usually not a problem, but sending to a lower baud rate device can lead to packet loss if you don’t use flow control.

4. 1 and 2mW Xbees sometimes are  just not good enough indoors.. They work, but you really need to be in line-of-sight. If you cant see the other XBee module, you probably will have some problems. Because of this limitation, I now use  50mW xBee Pro modules for almost everything. The difference is awesome – from across the room to across the street.

5. The wire whip antennae is pretty fragile. Don’t be surprised if it pops off. (It did within the first 10 minutes of owning one with a wire whip.) The simple solution was to simply solder it back on. I’m not sure if this can affect the signal strength, but I’ve seen no problems.

6. Use the chip antenna only if you need a lower profile. I’ve had some weird problems where my chip antennae xbee wouldn’t receive unless I pointed the top of the antennae towards the source. No problems with the wire whip.

7. Xbee’s are half duplex. This means it can either send or receive at any given point, and not at the same time. If you need a full duplex device, check into other wireless technologies.

8. If you are having “lag” even though there is a good connection, then check how you are sending data and receive data from the Xbee. I was using Java and kept writing directly to the stream when I noticed a significant lag in sending and receiving data. I thought it was the Xbee until I wrote to the stream’s buffer instead of directly to the stream output.

9. Xbees can generate quite a bit of noise in your power supply, so always use with a good low pass filter on VCC and ground.

Hope this helps whenever you are choosing the right Xbee module for your next project. Hit up the comments if you have any questions!

I’m a code monkey. I liked to program because everything I produced was (virtually) free. I programmed maybe 20% of the time I was at a computer for the past 7 years. It started to get kind of old, but the thought of creating and hacking at things still lived in me. I wanted to build something physical that can interact with other people. I knew I had to learn electronics, but I didn’t have the time or the idea on where to start.

1) My first bit of advice is College. I’m currently attending Tennessee Tech University as a Junior in Computer Engineering. The biggest point of college is to start you off with a career. You will end up learning at least 70% of all field-related knowledge while in the work force. If you don’t believe me, go up to a graduated engineer and just ask. It’s true. So, go to college but only use it as a crutch.

2) Can’t go to college? Well, experiment! Play with electronics, study how each component works, and make sparks!* The best way to learn something is by doing it. A little side story.. during Circuits I, I played with capacitors. They are basically “temporary” batteries that can store charge and release it virtually at once. This made sparks, even at low voltages. I had a lot of fun with those things, and a whole new respect for higher voltages (ouch!)

* Be reasonable, don’t get hurt. Don’t sue me for something stupid you did without research.

3) Make something! I suggest starting with an Arduino. These things are very basic microcomputers that you can program with any PC. What is great is that these things are the real deal. You can prototype plenty of electronics gadgets with them and the community is HUGE. If you ever have a specific problem there is a great chance someone already posted a solution on the internet. On top of all of this, an Arduino costs only about $30. From the same retailer (Adafruit Industries), you can also get an awesome experimentation kit for $85.

The build is currently a work in progress. I have only started to finish one of them. Since it is final’s week, I haven’t had much time to work on them. I will post the full source code, schematics, and videos sometime after Christmas break. Until then, enjoy the timelapse footage of me building the LED drivers one at a time with a short video of one set running the demo software.

So far I would like to thank TNTech’s Baja Team (specifically Frank Smith) for letting me use their shop and helping me with the metal forming. Mwhaha

Edit: I found a bug in my firmware used in testing that reduces the brightness by a half (I needed one more bit shift!) – so the video at the end of the timelapse doesn’t do much justice anymore!

Sparkfun Electronics will be giving away $100 dollars of credit for anything you buy from their online store (except gift cards) on Janurary 7th, 2010. What’s the catch? Well, you pay for shipping… and that’s all! Of course they cant just keep giving away stuff, so they free stuff will stop once they hit $100,000 worth of free credits.

I love SparkFun, and recommend them for anyone dealing with electronics. They have great tutorials on everything from how to solder through hole components to building a cheap guitar amplifier using opamps.

I’m still working on my latest project. More on that later
Andrew

Head over to Gerrit’s post about a simple DIY tool that can change your life when it comes to manually soldering even the smallest SMD packages. With almost no money you can make something that keeps those small parts in place while you solder them to the board. I haven’t yet gotten into the world of SMD packages, but I will definitely try this out when my next project comes around!

The basis of the blog is to share the quirky stories and realizations everyday engineering students make throughout college . It was just put online, and he already has a couple of posts. Check back on his site often, especially as the school year starts back up again! You never know what to expect!

UPDATE: Apparently I fail. Here’s the link: http://www.defectivengineer.com. You can always get it through the blog roll to the right on my blog

Also, I’ve been having problems with interference on my soundcard coming from the USB line. Every time a large load is switched, a small “click” can be heard on the sound output. Chances are, the relays are causing EMI and that is traveling up the USB cable, through my motherboard, and messing with my soundcard. I’ve tried ferrite beads, that did no work. If anyone has ideas, please comment!

There are two sides of this project, the hardware and the software. The hardware part was the easy part. Mike had an Arduino board laying around and I went to radioshack to buy a relay, a 9 volt battery, a diode, and a transistor. Thats basically all that is needed for the hardware side. I used the schematic found on http://www.glacialwanderer.com/hobbyrobotics/?p=9 to make sure I’m doing everything right. Putting this together only took about 2 hours.

The software side was a little bit more tricky. I tried two differently languages: MATLAB and C#. Both turned out to be quite a big failure. Then I stumbled upon Processing, which is basically an extension onto Java that made it easy for visual artists to create programs. Processing included a library called Minim, which had lots of built in features for audio analysis. I used the beat detection algorithm from Minim and then used that to send a signal to the Arduino board over USB to turn on or off the lights.

Basically thats all! Later I plan to find a better relay, something that lasts longer [solid state relay?], and then put it in a box so it is safer and looks better.

For now, enjoy the video!