I got an Arduino Mega 2560 for christmas, along with some L298N boards, identical to this one:
I'm trying to use them to power a Lego 9V train (not InfraRed, just power straight to the rails). This should be really simple, and the sample Arduino sketch works fine.
But I'm not getting enough power through the Motor Controller. First I tried a 10V power brick wired directly, but this only put out 4.8V - not enough to power the lego motor. Then I tried the same power brick through the lego train controller, into the motor controller - this put out 6V, but still not enough to make the motor work. Then I tried a 12V power brick to the motor controller, and it's still not enough - 6.2V came out at the pins. I tried multiple Motor controllers, multiple Lego train motors and multiple pins on the controller and arduino, but the results are still the same.
The Lego train motors only draw 0.2A at 9V when running, so it seems unbelievable that there would be so much power drop across the L298N that the motors just hum without spinning. Has anyone else come across this? Do I need a more powerful power supply?