Sweep and knob examples on sg90 servo

Other Hardware Robotics
1

I have tried these 2 examples as suggested by people on this forum. In both examples using the sg90 servo you get a lot of shivering of the servo at different places. This would not be good if you were trying to do delicate things with the servo. It may just be a problem with this particular servo.
It has been suggested that the current to the servo is too low. I don't believe this is the problem as I have used a 5v supply with a 4 amp capability. I bought a lab power supply especially so I could do this. The result is no different from my normal 800ma supply.
I have used another coding with much better results. Much less shivering. I have uploaded this. Can anybody comment on their own experience with sg90?
servo_test.ino (269 Bytes)

2

It would have been more convenient if you had posted your code rather than attaching it so here it is

#include <Servo.h>
Servo myservo;
int pos = 0;
void setup()
{
    myservo.attach(9);
}
void loop()
{
    for (pos = 0; pos <= 180; pos += 60)
    {
        myservo.write(pos);
        delay(2000);
    }
    for (pos = 180; pos >= 0; pos -= 60)
    {
        myservo.write(pos);
        delay(2000);
    }
}

There are fundamental differences between it and the Sweep example such as the number of steps in each sweep and the delay() between them so I am not surprised that it behave differently

3

Did you connect the servo ground, servo power supply ground and Arduino ground all together?

4

I should have also mentioned the knob example Bob. Shivering was occurring around 1v on the pot input. The rest of the pot movement was ok. If you were using a sensor input here instead of the pot you are going to be having the same problem when your sensor input is around 1v.
As I have said previously I am new to servo motor control. I would like to get these problems out of the way before going further. I want to, for instance, put in a light dependent resistor(LDR) in place of the pot in the knob example.

5

Yes, all ground Fungus. You have to be careful and makes sure of that. Perhaps the shivering problem is exclusive to the sg90 servo. That is why it would be great if I could have input from others on their experience with the arduino examples and using sg90. There might be a better servo out there without that problem.
I am using a 100uf, 16v capacitor across the power lines of the servo. I will try a bigger capacitor. A voltmeter attached to the control of the servo gives a steady voltage. No fluctuating voltage to indicate that the servo is shivering.
It may be in the gears. They may not be fine enough causing a bouncing back and forth.

6

Maybe you have got a poor quality counterfeit SG90 servo.

From the manufacturer's website:

There are many counterfeit servo of TowerPro from China dealers selling on eBay, Amazon and Alibaba websites.
If the suppliers removed “TowerPro” logo from the photos and the products description, they are selling counterfeits low quality servo.
Please identify the supplier before you purchased the goods. Only our authorized dealers who provide reliable quality servos and after services.

7

Unfortunately there is not such a thing as "the sg90 servo" because there are many, many cheap and nasty clones of it around. It has become the name for a servo of that size and you cannot rely on its quality

One factor is the quality of its internal potentiometer and gear train. Are the gears metal, for instance and how much backlash is there in the mechanism ?

8

Thanks Bob. Could be a nasty clone. Bought it through JAYCAR. Thats not to say its not a clone I suppose. Backlash is the word I want for the shaking I get at certain points in the movement. Can you recommend a good one available through a reputable supplier? I am in Australia. From your name you may be in the UK.

9

The servos associated with RC are generally reliable and accurate. In the UK I would favour buying these servos for a serious project, but don't know about an Australian source

Note that they are metal geared servos

Are there any reputable suppliers of RC equipment that you know of ?

10

Thanks Bob. I will try to locate the one you are recommending.

12

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