actually, I'm working on a project that contains 2x(12v gear motors )
I connected them to L298 H-bridge board and then to Arduino
I tested them working both at a time (knowing that I connected a 12v power supply to the module)
and they seem a bit slower and that because each motor needs 12v
so I decided to connect a 25v power supply to the module instead of 12v, and I know that I should remove the jumper when using more than 12v
the problem is, whenever I remove the jumper the module turns off, but as soon as I put back, it works , but I can't leave like that because it will burn the regulator ..right?
Without the jumper you will have to supply the module with 5 volt logic power from somewhere, I won't suggest your Arduino without knowing more about that particular module, can you post a link and or picture? Also, what is 25V going to do to your 12V motors?
EDIT: If your 12V supply cannot hold up 12V with both motors, best solution is a more powerful 12V supply. And don't forget, the L298 is going to drop 1 or 2 volts depending on current draw, if you get 11V to a motor you're doing OK.
I want to use 25v so that each motor operate at its full capability
because there is a 3v drop when each motor operate, and their movement is not stable enough as I can tell
but since you suggested using a powerful 12v power supply I will try that
Stall current of that motor seems to be 1.2Amp@12volt.
Make sure the supply can provide that current.
The L298 drops indeed a few volts in H-bridge mode.
You could compensate for that with the supply,
but I don't think a motor made for 12volt is going to survive 25volt for long.
Leo..