+5V or VIn is generally the 5V from the EZ-B Vm is generally the supply to the motors taken from the battery. Ground is always Ground, taken from any ground since it's a common ground.

Rich have a well written detail tutorial that can be found here

If you are supplying the +5v from EZ-B, it will power on, along with the EZ-board.

That looks familiar

I always stick to a single battery, if lower voltages are required then I use voltage regulators to reduce it to an acceptable level. This way, when you power on the robot everything comes on at the same time.

I wouldn't recommend taking the motor power (VM) directly from the EZ-B since this will probably brownout the EZ-B due to the load of the motors.

Like @Rich most of my robot designs use a single battery that is used to directly power both the EZ-B and the Motor Controller Voltage input. This way you get the max. voltage you can achieve going to your motors and you have a voltage that can be regulated down to a smooth 5V for the EZ-B circuitry.

To answer your second question, it doesn't much matter which you turn on first or second. There are probably several small reasons why one way might be preferred over the other but for all intents and purposes it really doesn't matter.

As an aside, the other day I was looking into the H-bridge wiring a little closer, and I found that the +5V line on the L298 motor controller is actually a regulated 5V out from the onboard voltage regulator. In my way of thinking I wouldn't attach the +5V line from the motor controller to the EZ-B in fear of having the 5V regulator on the controller jockeying for position with the +5V regulator on the EZ-B, just works both regulaters harder, but as long as the L298 board's switch is open it would be ok.

Leaving the +5V wire out, as was quoted above, you'd have to be mindful of the onboard ON/OFF switch was activated in order for the L298 to get the regulated 5V it needs to it's logic circuitry from the onboard regulator. Either way, it just boils down to personal preference really, one way just requires one less wire.

oops I Just notice, Sorry is it better to get power from battery running motors or ez-b?

I do not recommend tapping into your motor for power, Since the current Voltage fluctuate between high and low current.

thanks for the answers.

since I will be using two batteries. one to power ez-b and three h-bridges will get power from one battery pack. power for six motors from another battery pack (7.2 volts 2800mAh).

Again thanks for answers, just make sure that, what I thought was correct.

:)

j