I wonder if it would be possible to make a self-balancing robot with two IR range sensors.

The idea is, the robot is basically a stand-up board with two wheels, and on each side of the board, install an IR range sensor facing the ground.  Then, adjust the wheels according to the readings of the two sensors.

I am worried because I am not sure how accurate the IR sensors are.  Would this be possible?

This is exactly what I am planning to do, I am glad I found this as my guide. Thansk for sharing.

And that would be my first robot.  

I am having trouble using this installer, it gives me an error window.

Title: 16 bit MS-DOS Subsystem

Message: C:\User\xxx\AppData\Local\Temp\MPART1~1.EXE  The NTVDM CPU has encountered an illegal instruction.  CS:e700 IP:f0 cb f9 c3 f9  Choose 'Close' to terminate the application.

The error message has a Close button and an Ignore button, but they all terminate the installer.

Any idea?

Basically, I don't want to have an extra small board for the power regulation, that's why I want to replace the regulator on board.

Now, I think I've figured out all the variables in my project, and I am now ready to place in orders, and wait for the shipments.

Thank you ALL for your help.

Thank you, Mem and Eireen.

I've decided to go with 5 NiMH rechargeable batteries with battery holders (I will buy a 4-cell and a 1-cell and connect them together).

I did some reading on the LF50CV, as well as MC33269D-5.0 which is the regulator on the Arduino Duemilanove board.  The LF50CV has a drop-out of about .5V while the MC33269D-5.0's drop-out is about 1.0V.

So, I am thinking: can I just replace the on-board MC33269D-5.0 with a LF50CV?

BTW, here http://arduino.cc/en/uploads/Main/arduino-duemilanove-schematic.pdf is the Arduino schematics

I am working on my first robot project.  It would be a simple differential drive robot, plus two photoresistor to avoid dark or light.  

I choose to use Arduino as the controller, and two modified Hitec continues rotary servo to drive the wheel. I believe I will keep on other robot projects after this (like a bigger ones with more functions, and I will try DC motors, too), and I hope my investment now could also be used later.

For the Arduino, I believe it's better to use a power from 7V to 12V; while the best for the servo is 6v; and of course, it's also better to use two powers, one for the controllers, and one for motor/servos.

I will use a 9V battery (like this one: http://en.wikipedia.org/wiki/PP3_battery) for the controller, I didn't find a rechargable one yet (how do I recharge this kind of battery??).

I am still not sure what to use for the servos.  One option is to buy a battery pack (like this one: http://www.robotshop.ca/lynxmotion-bat-05-battery.html), then I will have to buy a charger for it, too, and they don't have any stock in RobotShop.ca (I am in Canada), I checked local The Source (the store in Canada, just like Radio Shack) and they don't have it either.  I thought about battery holders (like this one:http://www.robotshop.ca/sfe-battery-holder-4xaa.html), but I can only find those to hold either 4 or 8, which would be either 4.8V or 9.6V.  I also found this battery pack (http://www.liquidware.com/shop/show/BP/Lithium+Backpack+Stealth), it's quite impressive (especially the fact that I can recharge it using USB), while the price is quite impressive, too, cause I have to pay about $20 dollars to ship it to Canada (and don't know how much I have to pay for the custom yet).

Thank you!