External Power Source

Projects General Guidance
1

Hey, I,ll just tell you my task and you tell me what to do.

Scenario

  1. I have 5 servos 4.9v (Futaba S3003), each connected to an external power source, their GND is common with arduino.
  2. I have 5 potentiometer 10k, which I will use to control the servos.
  3. Two 24v DC motor also connected with an external power source via Relay.

My Questions

  1. Do I need to use separate power source for servos 4.9v and 24v DC motors? or a 24v battery would be sufficient, if yes then do I need to use step down the voltage for servos?
  2. Does potentiometer requires external power source, or I could directly connect it to 5v from arduino?
  3. What type of relay should I use? or lets just say I dont know what relay to use.
  4. If I am using 5v relay, can I directly operate 5 to 8 relays from 5v arduino? or I require again the external power source?

thats all, these are the question I have for now, I have tested different basic stages of arduino with LEDs and servos, so now increasing the difficulty level, your guideline would be helpful.

Thank you

2
  1. Do I need to use separate power source for servos 4.9v and 24v DC motors? or a 24v battery would be sufficient, if yes then do I need to use step down the voltage for servos?

Obviously a 24v supply would destroy the servos. You could step down to 5v with a switching supply often called a 'buck converter'. These are available on eBay at low cost. The supply could also power the Arduino. Draw current for the servos EXTERNAL to the Arduino.

  1. Does potentiometer requires external power source, or I could directly connect it to 5v from arduino?

Potentiometers draw small currents. Connect it to the Arduino.

  1. What type of relay should I use? or lets just say I dont know what relay to use.
  2. If I am using 5v relay, can I directly operate 5 to 8 relays from 5v arduino? or I require again the external power source?

Use 5-8 solid state 5V relays easily driven by the Arduino. The relays are 'powered' by the 24V source.

Why do you need so many relays with only 2 DC motors?

3

Why do you need so many relays with only 2 DC motors?

I need to use 5 relays for my another project.

thank you for the help

Conclusion

I can use 24v battery as an external power source to use two 24v DC motor via Solid state relays (or maybe mechanical relays), five 4.9v servos by stepping down voltage and also for arduino 9-to12v. Potentiometer does not require external power source as it does not take too much current and can be used directly by arduino.

My Project Details

I am making a robotic arm (very common these days) with 5 DOF, which will be mounted on a moveable trolley which can go to x,z direction (driven by 2 dc motors). A play station joystick is used to operate all these movements, the servo will be operated by the four potentiometer joystick, the two front button will operate the dc motor movement and so......

I hope you understand what I am doing, and will post the video once its completed, further if you guys have any guideline or suggestion, that would be very useful.

Thank you

4

I would not go with a cheap o voltage regulator for your servos.

  1. because they could pull a lot of current
  2. because the input voltage is high

Something like this would be best

You might also consider a motor driver to move your motors

5

I suggest you get a couple UBECs like below to power the servos at 6v for best performance. At 5v, the arm might not be able to support itself.

http://www.ebay.com/itm/Hobbywing-5V-6V-3A-UBEC-Switch-BEC-max-5A-Lowest-RF-for-Rc-Heli-Rc-Planes-HW3A-/321153340619?pt=Radio_Control_Parts_Accessories&hash=item4ac63b14cb

6

You might also consider a motor driver to move your motors
Speed Controllers

Actually, I am controlling this via voltage as it will complete my requirement but off course if someone want a better speed control then definitely you need a drive.

and thanks all