Unexpected servo behavior

Other Hardware Motors, Mechanics, Power and CNC
1

Hi there
Im getting started with arduino and Im making my first project, its about controlling a bunch of servers with a kinect following the closest point.
Im starting with a very simple exercise (Moving a servo from 0º to 180º) and I notice that the servo is doing a strange or unusual movement.

You can find the code for my exercise here: http://www.oomlout.com/oom.php/products/ardx/circ-04

I star with a small servo (The one that came with the starter kit from sparkfun heres the link, SparkFun Inventor's Kit for MicroView - SparkFun Learn) and it works just fine but when I upgrade to a bigger servo (Also from SparkFun Servo - Generic Metal Gear (Micro Size) - ROB-14760 - SparkFun Electronics) It make a strange movement.

Does anybody knows why?

2

iVinx:
when I upgrade to a bigger servo . . . It make a strange movement.

Does anybody knows why?

Probably because you're powering from the Arduino's 5V line. Servos require a lot of current and the Arduino's regulator can't supply enough.

3

Actually that was my first guest since at first the bigger servo didn't move at all, I plug in a extra power supply and then the servo started moving (Its a 9VDC adapter by the way)

4

Its a 9VDC adapter by the way

Most servos can't take more than about 7 volts, so you risk damaging yours with that adapter.

The general recommendation for servo supplies is 5-6 volts, capable of at least 1 ampere per servo.

5

My guess is iVinx is using the 9V power to the Arduino's barrel jack and powering the servo from the 5V line.

This will save the servo from burning out but might kill the Arduino.

@iVinx, I second jremington's advice about the servo power supply.

6

Thanks for the replay,
So what your saying is that the 9V adapter is making that noise? and Its posible that I burn my arduino with that adapter?

If I use a 6V adapter the problem will be solved?

7

A 6v adapter can power the servo. It is borderline for the Arduino but it will most probably work if it is also powered from 6v.

8

Ok, Ill try this.

I'm trying to do something like this:

I already have the algorithm that detects the moment of several points and now I need to mode each panel according to the distance between the point and the panel.

Can anybody orient me of this subject?
I did the prototype with one servo and it work just fine but now I need to use more and I don't know how.

9

You need to understand how much power the servos use. What is the maximum voltage they need? How much current do they draw?

I've been looking at servos recently and it's easy to find their voltage specification but hard to find current. They're usually powered from batteries and batteries can deliver a lot of current when required, so the servo people don't really care about peak current. Depending on the size of the servo, I would expect to need at least 2 amps per servo. So you need a 6V power supply of 8 amps, just for 4 servos. That's a pretty big power supply.

10

Attached pix shows how to power the servos.

servo power.jpg