My circuit Consists of:
- Arduino Yun: http://arduino.cc/en/Main/ArduinoBoardYun?from=Main.ArduinoYUN
- Arduino Motor Shield rev3 : http://arduino.cc/en/Main/ArduinoMotorShieldR3
- 12V Lead-Acid Battery like this one http://gnarlyparts.ca/images/040-BATT1-2_w450.jpg
- Step Down regulator 12V -> 5V: ( http://www.robotshop.com/eu/pololu-step-down-voltage-regulator-d15v35f5s3.html )
Output of voltage regulator (5V) is connected to motor shield screw terminal (Vin,Gnd) and motor shield passes the power to Arduino. Both Arduino and Motors are powered with 5V.
After connecting power to input of voltage regulator Arduino Yun flashes green LED and shuts down. This happens about 50% of the times. In other cases Arduino starts up properly and circuit is working as expected for hours.
What could be the cause of Arduino shutting down fraction of a second after connecting power? When I powered separate Arduino Yun witch micro USB phone charger this problem didn't happen, but with motors and shield I need too much current for powering with microUSB. The voltage regulator I use is quite reliable i think.
I attached capacitors for decoupling, but it didn't help. the circuit looks like this: