You have no delays in the display of the letters.

Let's say that you display AA and then BB immediately afterwards. What you will see is BB because the change is so fast your eye does not perceive that AA was ever there. Also remember that at the end of loop() you can imagine that it immediately starts at the top again, so in the example you have all you will ever see is ECE (because you have a delay there) and CCC (if it existed) would immediately be replaced by ECE (or Clear in your case).

You should put your code in a code 'box' on the screen. Use the # tool in the menu when you post.

I don't see a CCC function? Have you posted all your code.

LED = LOW just makes the variable LED the number 0. You need to use the digitalWrite() function if you are trying to make the ouptut of pin LED LOW.

Try defining the LED variable as a const (which it should be) and your code will not compile.

I know it is not preferred style for most of the Arduino code I see, but using #define for LED will immediately highlight the problems.

Try the Multi_Blink example in the Playground.

Generally standard servos just rotate 180 degrees. I have seen posts where people have modded the servos to do complete turns, so Google could be your friend here.

If you want to run wheels and you already have a motor shield, then why not just use a standard DC motor or a stepper motor? These can be run from the Arduino thru the motor shield. Examples in the Playground.

My understanding of the 't' is it stands for 'type', as in datatype.

Servo will have 3 wires - +V, Gnd and a signal. The signal needs to be pulsed to move the servo, with specific timing. There is a Servo library that does this work for you as part of the Arduino IDE install, and there is information in the Playground on how servos work.

http://arduino.cc/playground/Learning/SingleServoExample

Looks like the bit you highlighted was the plug? No idea where you get one, but I would just poke some wire into the servo socket and use that if you are building a temporary circuit to test your ideas.

The white thing is a breadboard and you can get those in any elecronics store, ebay, etc.

Duemilanove (2009 in Italian) is for this purpose no different to the Uno. I think it is just a 'older' model with a different CPU.

You don't need a motor shield for a servo, but you do need a seperate power supply for the servo as the Uno can't provide enough power for itself and the servo.

Servo will have 3 wires - +V, Gnd and a signal. The signal needs to be pulsed to move the servo, with specific timing. There is a Servo library that does this work for you as part of the Arduino IDE install, and there is information in the Playground on how servos work.

http://arduino.cc/playground/Learning/SingleServoExample

From your brief description my guess is that your pinout for the LED matrix are not the same as the example you are following. You should get hold of the data sheet for the matrix and check that logically you have connected to the rows and columns as you expect. Once you have verified that the hardware is connected properly, then the software is the next step.

Define your own function with the code inside it.  Look up any reference for C to work this out.

The Arduino is not accurate as a clock over a long time. However, as you are in control of the lights, maybe when the lights come on you can just use the Arduino time to work out the current time. The sort of logic I am thinking of would be that is the lights are not energised, use the external clock (I2C) and if the lights are on, use the last reading and add on the time elapsed from the Arduino. When the lights are turned off the Arduino can resync to the external clock.

If it is RF interference, then maybe position the electronics further away from the lights? Or change the lights to something else :-).

It depends on what you mean by 'garbage' values.

Time is a very linear thing, so one time value will aways be bigger than the previous time value. I would have thought that in the software you should be able to ignore values that differed from the previous one by more than a certain amount as being 'in error', and anything less than previous reading as being definitely wrong.

IMO

You need to do one thing in the while loop - refresh the value of state with the current value of the variable so that when it changes you will exit the loop.

As it is it will never exit because the value of state never changes.

Shaft encoders don't need to be directly on the shaft that is being measured. You can drive them through gears or a belt (toothed preferably to minimise slippage) from the main shaft onto a secondary shaft in a more conviennt location.

If you have less than 360 dgeree rotation then maybe a pot will be sufficient - measure the resistance/voltage on the pot to infer the angle - but accuracy may be an issue if you are trying to accuratley position the robot arm.