Hi everyone,
I want to power up 4 12v-motors and 4 6v-servos. For now I have a regulated power supply, but later I'll use a 11.1v Lipo-battery instead. I'll connect 11.1v battery to the motor driver and to a breadboard which is connected + and - cable from 4 servo. The motor driver has 5v regulator for arduino.
I did 2 separated trials. One with motors, one with servo.
For motor it needs at least 0.6-0.7 A to move the robot ( certainly, with 11.1V). While running it needs from 0.4 to 4 A ( max current of motor is 7.5 A) . (That's for all 4 motors)
For servo, it needs 6v and 0.14 A to hold the position and 1.32A to turn. For all 4 servos
I wonder how to limit the power from 11.1V with 0.4-4A to 6V with 1.3A
Thanks in advance
Fang,
What motor controller are you using?
Hi,
this one here
http://robokits.co.in/shop/index.php?main_page=product_info&cPath=73&products_id=342
with this motor
http://robokits.co.in/shop/index.php?main_page=product_info&cPath=2&products_id=328
You need one of these for the servos.
and run the motors directly from the battery. If that does not give you enough voltage to run the motor correctly then use one of these:
Your title is wrong you do not want to limit the current you just want to regulate the input voltage.
Fang,
The motor controller you specified only works for brushed DC motors. You will need a different motor controller specifically for servo motors. I use this one from Pololu all the time and its fantastic, easy to use, and cheap:
They make them with different amounts of channels (up to 24) for controlling more motors. You will need one of the step-down DC/DC converters that Grumpy Mike listed... one that can accept 9.6-12.6V input and that has an output of 5V with at least 1.5 amp max output current. You need the 9.6-12.6V input range because a 3 cell LiPo battery can be as low as 9.6V (fully discharged) and has high as 12.6V (fully charged). The DC/DC converter will make sure that that servo will have a continuous 5v no matter what the LiPo voltage is.
Servos specs are typically given using 6 volts, but most people just power them using 5v, which is just fine. The servo won't be able to give as much torque or move as fast as it could at 6v, but there aren't really many DC/DC converters that output 6v so you will have to just work with 5v.
Making sure the DC/DC converter has a high enough output current is important. If your servo draws 1.4 amps, you want to make sure the DC/DC converter can supply that much current. Also, heads up, using 5v instead of 6v will draw a couple hundred more milliamps.
Hi,
Thank to all for the suggestions.
I know what to buy and what to do now XD
Have a good day
ps:@mike: title is changed
Fang,
Just to double check, you are using both a brushed DC motor and a servo motor in your project, correct?
The brushed DC motor and motor controller you listed below will work together just fine:
white_fang82:
Hi,
this one here
http://robokits.co.in/shop/index.php?main_page=product_info&cPath=73&products_id=342
with this motor
http://robokits.co.in/shop/index.php?main_page=product_info&cPath=2&products_id=328
However, for a servo motor like this one, you will need the Pololu Maestro that I posted about earlier.
not a, but 4, 4 motors and 4 servos, certainly with a arduino mega.
my serso is hs-5485hb. Do I really need the Maestro, when I can control the servo with Arduino?
Correct me, if I'm wrong. The Maetro is almost as same as a a microcontroller like arduino. Also It's used to control servo.
While the arduino has the ability to control a servo, it is not designed specifically to do so. The Maestro's entire purpose is for controlling servos, so it has a ton of important and helpful features that will make your life a lot easier in the end, especially when it comes to controlling 4 servos at the same time.
You can control the Maestro from your Arduino using serial communication.
Ah ok, I'll try it . Thanks 
pcdangio:
so it has a ton of important and helpful features that will make your life a lot easier in the end, especially when it comes to controlling 4 servos at the same time.
That's debatable - if you can code a state-machine you won't have any difficulty driving
N servos at once surely?
I wonder how to limit the power from 11.1V with 0.4-4A to 6V with 1.3A
Search on ebay for a UBEC. These are made for powering servos from higher voltage batteries and are very efficient. I doubt you need an external servo controller unless your arduino code is complex. You can always get a servo controller if you have issues directly controlling the servos from the arduino.