Power Supply of Multiple Servo Motors

Other Hardware Motors, Mechanics, Power and CNC
1

Hi All.

I would like to get opinions or guidance on the electrical design involving 6 Servo motors. There are 5 FS5109M(FeeTech FS5109M Servo Specifications and Reviews servos and 1 Towerpro SG90(http://www.towerpro.com.tw/product/sg90-7/)

I know I'm going to need an external power supply for the motors. I am looking at a 2 cell 7.4 V LI-PO rechargeable battery. Additionally, I'm looking at placing a voltage regulator before each servo motor to avoid current issues. My idea is to use 5V and 3.3V voltage regulators, that produce a maximum current of 1A, for the FS5109M servos and the SG90 servo, respectively. Please view the schematic below if the explanation was unclear.

Firstly, can this design work? Secondly, will this affect motor performance because I am limiting the voltage supply under that of the rated voltage? and lastly, are there better ways to do this in terms of circuit protection and adequate current supply?

Also, I have read on the forums that it is good practice to keep the motors and the microcontroller on separate power supplies. However, if I was to use a voltage regulator before placing power into the Arduino 5V pin, would this acceptable and safe?

Thank you all in advance.

Motor Voltage Reg sketch.jpg
Motor Voltage Reg sketch.jpg1575×840 102 KB

2

I can't see any point in having multiple voltage regulators, certainly not 7805-style linear regs. And I doubt if 1A per servo is enough for those FeeTechs.

Also why do you want to run the SG90 at 3.3V? It will be ridiculously slow and weak at that voltage. It may not even work reliably.

A single high current switch mode DC-DC converter might make more sense. Polulu have a few good ones or you could use one of the BECs intended for RC models. Castle Creations do an excellent 10A BEC.

Steve

3

Hi there, thanks so much for the helpful reply. I like the suggestion of a DC-DC converter. My concern is will a single DC-Dc converter be able to deliver enough current if all servos are used simultaneously. Also, the micro servo will be powered with 5V - I have no idea what went through my mind to power it with min rated voltage.

Although BECS are really nice and convenient, they are rather pricey in South Africa for good quality. Additionally, this system forms part of a bigger project with a limited budget.

4

If you can find a DC-DC converter with the ability to deliver at least 10A it should be fine.

I generally use BECs for the convenience and because I'm used to them from RC models. But I have no idea about pricing and availability in South Africa.

Steve