I'm building a lunar lander game. I need to measure roll and speed/direction of the lander to sense a crash or hard landing. It would be nice to measure the altitude but that would probably be too hard since the terrain varies. Nonetheless, I want to use an IMU but find there are many choices (looking on sparkfun) and I don't know which to get. I see some have an arduino on board. Can I write all my code in this arduino or is it dedicated to the sensors? Or should I get a simple sensor board and interface it to an arduino I already have?
I can see only 8 IMU's at Sparkfun : IMU - SparkFun Electronics
Check also the IMU section here: Accelerometer, Gyro and IMU Buying Guide - SparkFun Electronics
The onboard Arduino is arduino compatible hardware with sensors. So you can use it as if it was an Arduino, and if you use the sensors or not, that's just up to the program (the sketch).
But you do need 3 accelerator axis and 3 gyro axis. Some older sensors have only 2 axis.
If you use the onboard Arduino, you have a very small and nice circuit board.
However, this one : https://www.sparkfun.com/products/10736 is running at 8MHz, while most Arduino boards are running at 16MHz.
If you use your own Arduino, it is easier to upgrade to an Arduino Mega.
If you want it to be really cheap, look for "MPU-6050" on Ebay, it costs 10 dollars/8 euros. But that sensor is not easy, read this: Arduino Playground - MPU-6050
Do you understand this : http://arduino.cc/forum/index.php/topic,58048.0.html ? If you don't, you better find something with a good example sketch.
My advice: I would prefer an Arduino Uno (it is the most common Arduino board) and I would add a I2C gyro/accelerometer breakout board. But only if you have enough space for it. If you want it to be small, use the onboard Arduino compatible one.
You could measure the altitude for small heights with sonar (ultrasonic,ping), or an IR distance sensor or a laser. For larger heights, you could use a sensitive baromic sensor.
Very good information Krodal.... Thank you very much!
BTW - I don't think I need 3 accelerator axis and 3 gyros but I will probably get a board with that many since they are cheap. The lander is mounted to an arm and can only move in two dimensions plus roll side to side.
That sounds like 3 axis to me !
The way I saw it, it was 2 accelerators and 1 gyro. 1 accel for up/down, 1 accel for left/right, 1 gyro for roll left/right.