user7343: 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 "components at a time" 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.

user84: Here are a few suggestions that might help:

Provide its own power supply to Arduino UNO, so that no voltage drop can occur on the board itself due to high energy consumers as servos and DC motors. As someone suggested in an answer, a voltage drop on Arduino MCU may trigger the Brown-Out Detection (BOD) which will stop the MCU until voltage rises up again, above a given threshold. You could for instance power the UNO with a 9V battery (or the equivalent 7.2V rechargeable pack). Those batteries don't have much energy but it should be OK as long as they are not used for powering motors. Of course, then you'll have to remove the Vin wire to your 8-batteries pack.
Add decoupling caps (between V+ and GND) as near as possible to every energy consumer: that means adding decoupling for each motor driver power-in pins, for each servo power pins, and ALSO for the HC-SR04 sonar sensor (in my experience, it can drop voltage a lot, more than you could expect); note that you may also need decoupling for the camera, but I'm not sure on this one, because I have never used one yet.

Note on decoupling caps:
The value of caps to use depend on many factors, which would be too long to explain here (and I admit that I don't necessarily understand each of these); but typically, you would use a small cap (100nF) when you expect fast (and short) voltage drops, and a bigger cap (>=10uF) when you expect longer voltage drops. 
When you don't know, you can just experiment and see what works best. 
Using both kinds of caps at the same time (in parallel) does no harm (I have done this in several situations).
For higher caps, you will have to use an electrolytic cap, which is polarized: do make sure that you wire them correctly (+/+, -/-) otherwise they may blow up.
Also, choose a breakdown voltage for the cap that is much above (I'd say 50% above is fine) your power voltage; 16V is a common value that would fit your needs; of course, you can use higher breakdown voltages as well.

user7508: From the Servo library documentation:

On boards other than the Mega, use of the library disables analogWrite() (PWM) functionality on pins 9 and 10, whether or not there is a Servo on those pins.

This is, as has been suggested, because of conflicting usage of the timers. You should just move your DC motors to other PWM-capable pins.

user4169: 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

7343: <p>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.</p>
<p>Of those 7 output pins, 4 are PWMs for the motors (don't ask why), 3 are for servo control (tower pro mg-995)</p>
<p>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).</p>
<p>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.</p>
<p>I've read from <a href="http://www.ruggedcircuits.com/10-ways-to-destroy-an-arduino/" rel="nofollow noreferrer">here (method #10)</a> 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?</p>
<ul>
<li>Edit +</li>
</ul>
<p>Here's how the circuit looks.
<img src="https://i.stack.imgur.com/ccwHt.jpg" alt="enter image description here" /></p>
<p><strong>Edit:</strong></p>
<p>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.</p>
<p><strong>Edit:</strong></p>
<p>Here's some images on the Pixy camera</p>
<p><img src="https://i.stack.imgur.com/DznXd.jpg" alt="enter image description here" />
<img src="https://i.stack.imgur.com/Vhond.jpg" alt="enter image description here" /></p>
<p><strong>Edit:</strong></p>
<p>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 <code>servo.attach(servo_pin)</code>  code everything works fine.</p>
 84: <p>Here are a few suggestions that might help:</p>

<ol>
<li><p><strong>Provide its own power supply to Arduino UNO</strong>, so that no voltage drop can occur on the board itself due to high energy consumers as servos and DC motors. As someone suggested in an answer, a voltage drop on Arduino MCU may trigger the Brown-Out Detection (BOD) which will stop the MCU until voltage rises up again, above a given threshold. You could for instance power the UNO with a 9V battery (or the equivalent 7.2V rechargeable pack). Those batteries don't have much energy but it should be OK as long as they are not used for powering motors. Of course, then you'll have to remove the <code>Vin</code> wire to your 8-batteries pack.</p></li>
<li><p><strong>Add decoupling caps</strong> (between <strong>V+</strong> and <strong>GND</strong>) as near as possible to every energy consumer: that means adding decoupling for each <strong>motor driver</strong> power-in pins, for each <strong>servo</strong> power pins, and ALSO for the <strong>HC-SR04</strong> sonar sensor (in my experience, it can drop voltage a lot, more than you could expect); note that you may also need decoupling for the <strong>camera</strong>, but I'm not sure on this one, because I have never used one yet.</p></li>
</ol>

<p><strong>Note on decoupling caps</strong>:</p>

<p>The value of caps to use depend on many factors, which would be too long to explain here (and I admit that I don't necessarily understand each of these); but typically, you would use <strong>a small cap (100nF)</strong> when you expect <strong>fast (and short) voltage drops</strong>, and <strong>a bigger cap (>=10uF)</strong> when you expect <strong>longer voltage drops</strong>. </p>

<p>When you don't know, you can just experiment and see what works best. </p>

<p>Using both kinds of caps at the same time (in parallel) does no harm (I have done this in several situations).</p>

<p>For higher caps, you will have to use an <strong>electrolytic cap</strong>, which is polarized: <strong>do make sure that you wire them correctly (+/+, -/-) otherwise they may blow up</strong>.</p>

<p>Also, choose a <strong>breakdown voltage</strong> for the cap that is much above (I'd say 50% above is fine) your power voltage; <strong>16V</strong> is a common value that would fit your needs; of course, you can use higher breakdown voltages as well.</p>
 7508: <p>From the <a href="http://arduino.cc/en/reference/servo" rel="nofollow">Servo library documentation</a>:</p>

<blockquote>
  <p>On boards other than the Mega, use of the library disables analogWrite() (PWM) functionality on pins 9 and 10, whether or not there is a Servo on those pins.</p>
</blockquote>

<p>This is, as has been suggested, because of conflicting usage of the timers. You should just move your DC motors to other PWM-capable pins.</p>
 4169: <p>My experience of high power draw from an Arduino is that it endlessly re-boots so maybe not the issue for you.</p>

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

<p>You could try a different Servo library.</p>

<p>This <a href="https://stackoverflow.com/questions/18705363/arduino-uno-pwm-pins-conflict">article</a> is useful to understand the timer/pwm/pin relationships</p>
