Measure total microcontroller current? So I have a Duemilanove board and am utilizing 7 output pins, I power a Pixy camera and pan/tilt servos from the ICSP header, i also power an HC-SR04 sonar snsor directly from the board.
Of those 7 output pins, 4 are PWMs for the motors (don't ask why), 3 are for servo control (tower pro mg-995)
when I try to output these 7 pins simultaneously things don't work, i get &quot;components at a time&quot; behavior. Like servos turn first, then the motors spin (servos stopped).
Initially we thought it must be a power supply problem (8 1.2v NiMh bat series) which powers the l298n h bridges (two of them) and also powers the board and servos. But now im starting to fear that it's the board itself and that it can't handle simultaneous outputs.
I've read from here (method #10) that taxing the board more than 200mA is a problem. But what exactly happens if you do just that? And is my case exactly like this one? If so, how to fix it?

Edit +

Here's how the circuit looks.

Edit:
Yes i do think there is a need for decoupling capacitors but im not sure where to put them. They dont seem to work. The bounty goes to the best answer on the proper decoupling of this circuit.
Edit:
Here's some images on the Pixy camera


Edit:
Actually from the original problem I noted when I posted this question, things don't work as expected. WHen the big servos move, the pan/tilt camera don't move when they are supposed to, or the motors briefly stop. I'm wondering if is also an Arduino idiosyncrasy because when I don't run the servo.attach(servo_pin)  code everything works fine.
My experience of high power draw from an Arduino is that it endlessly re-boots so maybe not the issue for you.

The Servo library and PWM pins are probably sharing the same timer therefore motors stop while servos are running.

You could try a different Servo library.

This article is useful to understand the timer/pwm/pin relationships