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I have 4 batteries which is two 12v and two 6v which i used to power my 4 motors.. stepper, servo, and two dc motor.. my stepper can operate ranging from 6-12 volts.. my two dc motors are 6volts amps of 2A. my servo is 6v-1ampere... im using arduino to control the 4 motors. everything works fine.. but....

i wan to supply my motors with only one power supply because 4 batteries are way too heavy.i'll be using an adapter with an output voltage of 12v and 1amp as my main power.. how can i supply all of my motors with one supply only and still operate the same as with using  4 batteries.. i'ts like it's centralized.. thanks..

[Reply #1 on:]

Use a 12V battery.
Use a switching power regulator to drop the 12V to 6V for driving the lower-voltage motors.
Optionally, use another switching power regulator to drop the 12V to 5V for inputting to the VCC/+5V of the Arduino (to save the loss of the linear regulator on the DC-in.) Else just run the 12V into the Arduino DC in jack, too.

Warning: your 6V converter needs to be rated for enough current -- looks like at least 3A in your description.
Such converter are generally pretty big/expensive (compared to simple components like a 7805 regulator.)
Some people would recommend you go to a hobby store and search for an "UBEC" circuit (ultimate battery eliminator.) These are usually cheap switching regulators built in China, and typically over-rated. If you find one that says "up to 5A" it probably has a 3A part on it, and not enough heat sinking to actually deal even with that under heavy load. However, it is a cheap way to get started. When it burns out, get another one, or get the industrial version :-)

[Reply #2 on:]

Can't. 12 V at 1 Amp is 12 Watts. The motors you list are 30 Watts. You would be better off trying to supply 6 volts at 6 amps( assuming the stepper is less than 1 amp...). That's what your motors would all want if they are running at the same time...

[Reply #3 on:]

Else just run the 12V into the Arduino DC in jack, too.

Can i also do it at the Vin input pin of arduino?.. and what's the max current and voltage can be supplied in the Vin?

[Reply #4 on:]

can i use LM317 for the 4 motors?.. split them 12v = 4 LM317 = 4 Motors.. one Lm317 for one motor?

[Reply #5 on:]

can i use LM317 for the 4 motors?.. split them 12v = 4 LM317 = 4 Motors.. one Lm317 for one motor?

A LM317 <--- max current 1.5 A.... No WAY... 

Here an idea... buy a lead-acid 6 V motocycle battery. And wire the motors direct - with the motors controller.   

[Reply #6 on:]

Here an idea... buy a lead-acid 6 V motocycle battery. And wire the motors direct - with the motors controller.   

but what i need is a plug supply.. i have power supply unit that i got from my computer but it's way too big to fit my system..

[Reply #7 on:]

So you want a supply from the main ( 120 / 220 ) ? right ?

[Reply #8 on:]

So you want a supply from the main ( 120 / 220 ) ? right ?

I have an adapter that will be plugged to 220 that has an output of 12v with 1 amp.. i want it to be my main supply for the 4 motors.. but if i want to supply from the main what should i do?

[Reply #9 on:]

Else just run the 12V into the Arduino DC in jack, too.

Can i also do it at the Vin input pin of arduino?.. and what's the max current and voltage can be supplied in the Vin?

Yes, as long as it's not the VCC/+5V pin. The main idea is to send it in ahead of the power regulator, not after it :-)

Current is never "pushed" -- the Arduino will draw what it needs. If you try to draw more than about 200 mA THROUGH the Arduino, it may fry the chip. This is why you use buffers and transistors and driver chips on the output when driving strong things like motors.

You need a regulator that can provide at least 5.5A 6V. That's a *lot* of current; most regulators don't do this. You'll probably end up with a "power supply" more than a "regulator."
Although you can get a number of 3A regulators, and use one per motor. However, using linear regulators like that is a big waste of power -- you'll burn off half your battery power in heat before it even gets to the motor. Use a switching power supply instead.
Also, if you are driving the motors with PWM or stepper controllers or similar, you want more voltage available to the controller than the ratings of the motor, and then want to current limit the motors instead. With the right drivers, you can run the 6V motors directly from 12V, without needing a step down at all.

Here's a 5A power converter that can go from 12V to 9V, for $19: http://search.digikey.com/us/en/products/APXW005A0X3-SRZ/555-1172-1-ND/2341120

[Reply #10 on:]

jwatte is correct. You need a "bigger" supply. You need a supply that provide : Motor 1 = 2 A, motor 2 = 2 A , servo = 1 A and step-motor = 2 A <-- Assuming

Let see..   2 + 2 + 1 + 2 = 7 A  <-- Need a supply to provide at LEAST 7 A. 

I don't know what type of stepper motor you have, therefore I don't know what voltage is need. I have a few, they operated at 12 V ( come from 5 1/4 drive ). Motors are not picky about voltage regulation. But the Arduino is very picky.