Right way to power Servos and DC Motors

I am trying to run an Arduino Uno with 2 DC Motors (300 RPM) and 2 Servo Motors (4.8-6 V). I have to make it wireless (using Xbee) so obviously I can't power it via USb. Which battery should I use for powering the Arduino ? And how do I give the external power supplies to the Servos and the DC Motors? Here's what I thought. Please correct me if I am wrong! Use 9V battery for powering the Arduino. Using 12V Li-Ion 2200mA battery to the Motor Driver L239d for the two motors. Connecting the same 12V battery to the 2 Servos. After reading a lot, I read something about conencting the grounds of the Servos and the Arduino. What does that mean? Thanks in advance!

The Gnd, or battery -, of all devices must be connected together so all electronics have the same reference point for 0V.

Power 4.8 to 6V Servo from 12V is probably not going to be good for them.
You can however use a DC-DC Switching Regular, or Stepdown regulator, to make a 6V supply pretty efficiently from 12V.
Check the regulators at www.pololu.com
You may need an amp (rule of thumb) for each servo when it is starting to move, or is moving, so use a regulator with sufficient current capacity.

read something about conencting the grounds of the Servos and the Arduino. What does that mean?

Read about it here:- http://www.thebox.myzen.co.uk/Tutorial/Power_Supplies.html

Thank you @grumpy_mike and @CrossRoads! If I connect 2 Servos in series using the 12V 2200mA Battery, theoretically, Voltage will get divided and entire current will flow through them both, right? And then Ill connect the motor driver parallel to this series connection. Seems legit?

No you can not connect servos in series it will not work and connecting the control line to your Arduino on the top servo will damage both your Arduino and the servo.

After some research, I found a way to power both the servos. I am still not sure but seems good. The next problem would be powering the motors. So I’ll ask a few questions now!

  1. Can I use the 12V battery to power two 6V Servos simultaneously?
  2. If 1st answer is yes, can I use the same battery to power the motor driver?
  3. A 9V battery connected to a DC adapter power the arduino? I won’t be powering anything else from the arduino.

2servos.png

While that diagram is correct you can not use a 12V battery as the power supply because you will burn out the servos. To power different voltage requirements off the same battery you need to use voltage regulators to make the different voltages you require. You can use the 12V to power the Arduino their is no need to cut that down to 9V first.

Ill use a 6 volt battery for the Servos then.. 12V for the motor driver and a 9v for the arduino..

There is no need to use three batteries, that is not a very good thing to do.

So i should use a voltage regulator? I just have a 12V and a 9V battery… Two 300RPM DC motors + 2 Servo Motors and a Arduino to power… will the 12 volt be sufficient for them all?

After some thinking, 12V battery to the arduino and the DC motors. 6V battery to the servos, grounds connected. Seems good?

Well if it were me I would power the servos with a switching voltage regulator. Then you only have one thing to switch to power your circuit on. You don't have to bother with multiple batteries discharging at different rates, and the whole soupy stem is lighter and smaller with only one power source.

I got a 6V.. so I'll use that for now..if the system gets too heavy, ill use the regulator! Thanks for your help :)

A voltage of 6Vis too much to apply to the 5V pin and not enough to apply to the Vin pin of the Arduino.

6V for the servos and 12v to the arduino & motors. It's difficult to run it on a single battery..

OK one last time.

It's difficult to run it on a single battery..

No it is not. Get a 6V switching regulator to run the servos and feed the 12V into the Arduino power jack.

I have a 12V 2200ma Li Ion battery. I have to power 2 servos, 2 DC motors and an arduino. From what I have read, Servos require atleast 1 amp current to work properly. So should I still use the same battery pack? Will it be able to power everything. And sorry, but just the one last time :)

I have a 12V 2200ma Li Ion battery.

No you don't. You have a 12V 2200mA*H* Li Ion battery, do you know the difference? It means, simple mindedly, that it will supply 2200mA for one hour or 4400mA for half an hour or 1100mA for two hours. Or any such combination of current and time. ( just don't push this too far though ).

If you get a switching converter a 6V load that runs at 1A will only take just over 500mA from the battery.

From what I have read, Servos require at least 1 amp current to work properly.

That depends entirely on the servo. And what it is doing.

So should I still use the same battery pack?

Yes.

Will it be able to power everything

Yes.

Thank You grumpy. You have helped a lot! I am almost done with the hardware and electrical stuffs. Now I am stuck with the coding. I am making a remote controlled car which can grip and lift using servos. Now I am struggling with making the Xbees communicate!

OK I would start another thread on that.

Now I am struggling with making the Xbees communicate!

In the Networking and Protocols section.