I'm trying to control up to 8 DC motors, with each one having independent direction and speed control. I haven't selected the appropriate motor yet but it will be up to 24V and 2A maximum.
Will I be able to use 4 Motor Shields in one Arduino board or would I be better off building my own board? If the latter, could anyone advise me on what components I will need. So far I understand I would need a H-Bridge and some kind of PWM Driver per motor (Something like the TLC 5940 NT unit), correct?
The motor shields I've seen have had hardwired pinout configurations, so unless you used an intermediate patch board to map the pinouts, all the shields would do the same thing. I don't know of this is true of all motor shields, but the ones I've seen were like this.
With that many motors, you might find you could save a considerable amount of money building your own drivers rather than buying lots of shields. Implementing speed and direction control would involve some non-trivial electronic design, though. This sounds like the sort of thing that might already be solved in robotic circles so you might find it's worthwhile looking for Arduino controlled 'bots and see what they do for motor control. It may be you can find a suitable driver board off the shelf if you look in the right places.