In your first post you said that the rover is sloppily wired. I got my share of that today, and needed to perform some surgery on my rover. I was trying out a sketch and suddenly one motor stopped running. I was fearing the worst thinking that one of the FETs on the motor controller had given up. Turned out to be a loose wire... one of the wires going from the coil to the connector had come loose. There was almost no solder to be seen on that connection so it's no surprise it came loose. I've been working on an autonomous sketch using an ultrasonic sensor to detect obstacles. The code works but it keeps bumping into stuff. Think I need some more sensors and fancier code
What does ROV mean? Maybe you can also consider NRF24L01 modules (version with amp, not the small ones). I have a couple of those and they work very well above water, no idea how they perform underwater
Do you know how much amps the servos draw? You can use a voltage regulator to to get the voltage down to 5-6V for the servos. I wouldn't power the ultrasonic module straight from the battery, take 5V from your Uno.
Yes, I have seen those IC's. They are a nice solution, but only available in a surface mount package. To difficult for me to solder myself Sparkfun sells this http://www.sparkfun.com/products/8745 , based on 2 BSS138 fets. It's cheap but I'm in the EU, the shipping will be more expensive then the board itself. I've just put the 2 2N7000's and ADXL345 on a breadboard, and it works.
I want to connect an ADXL345 accelerometer and a HMC5883L magnetometer to the 5V I2C bus of a Mega1280 based board. I've used the ADXL345 by using 4k7 resistors between the I2C pins and 3,3V in the past. It worked but I think it would be better to make a logic level converter. I found the following pdf which shows a circuit how to make this. http://www.nxp.com/documents/application_note/AN10441.pdf (see page 4) I happen to have a couple of 2N7000 N-channel mosfets. Are these suitable for this application? (datasheet: http://www.fairchildsemi.com/ds/2N/2N7000.pdf )
You forgot the most important source of all... Ebay. I just love the Chinese sellers of electronic components on ebay, have not had any bad experiences. Takes some time to get here but you get free shipping from most.
Nice to see another Rover 5 I bought one a couple of weeks ago. I've managed to write a sketch that lets me remote control it through a Nrf24L01 wireless module. I'm using the Mega1280 based Dagu red back spider controller and motor controller. Power comes from a 2 cell lipo battery. Here's a video of mine:
I also have the version with 4 encoders/motors, but don't really have a clue what to do with the encoders
Then you need to keep a pc running all the time. Costs electricity You can buy a simple sd card reader for a couple of dollars on ebay. (I bought one from Hong Kong, for less then 4$ including shipping.) Hook that up to your Arduino and log to the sd card.