In know this has been discussed before and I just posted this experience in another thread. However I thought it's interesting and could help if easily found by a search in the future. If you don't like my double post of information, well, get over it. Just kidding, go ahead and squawk if it makes you feel better. Here it is:
I've decided to input the Vin voltage to my V4 EZB at just about 6.5 vdc. This voltage will run everything nicely I had previously attached to the digital I/O ports except my MP3 Trigger and the 2.5 Amp Motor Controller I bought from EZ Robots a while back.
I'm still not sure about the Vin voltage range of the 2.5 Amp Motor Controller but the first day I powered up my new V4 EZB I pumped 12dv through it and it seemed to work OK. At least it didn't have any short term bad effects. However to be safe I decided to use it's onboard voltage regulator and feed it's electronics from the external 12vdc I have connected to it for the motor voltage. I just disconnected the wire I had connected from the digital I/O pin (leaving the ground connected between the two) and pushed the little white button next to the connectors. Works great and the board gives itself the designed voltage needed.
Also that same day I burnt up my MP3 trigger by also pumping 12vd through it. However I plan to use EZB's on board audio and attach it to an amp. I didn't cry over that brain fart to much. *blush*
So now I'm going through and double checking all my voltage requirements on all devices attached and being fed off the digital I/O ports. Like I stated above; looks like I'll be ok now with about 6.5 vdc. I have this adjustable voltage regulator between my 12vcd power supply and the EZB V4. About 9 USD on Amazon:
Dork Buck Regulator
Module Model:LM2596 Buck Converter+Voltmeter
Input Voltage: DC 4.0~40V
Output Voltage: 1.25V~37V
Output Current: 2A(normal and stable), 3A Max.
Display Color: Red
The above regulator is not the only thing out there. so if you want something like this simply get one that will give you the voltage and amperage you need.