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Author Topic: ES08A range of travel not 180 degrees?  (Read 1367 times)
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Hello, Everyone.

I am very new to Arduino and a first time poster on this forum.

As I began playing with my Arduino (Uno R2) and trying out some example sketches, I saw some strange behavior with the Servo > Sweep example.  It seemed that the sweep would start fine, but then near the end of the angle-increment cycle, the servo would jump ahead and sort of get stuck briefly before beginning the angle-decrement cycle.

I tried both ES08A servos which came with my Maker Shed starter kit, and the result was the same.

Here is the setup:

Arduino Uno R2 connected to Windows PC via USB
5VDC wall wart positive lead to servo positive, ground to Arduino ground
Servo ground to Arduino ground
Servo control line to digital pin 9 for PWM

With the example "Sweep" sketch I saw an issue near the end of the sweep toward 180; it was not possible to tell exactly at what angle.

Using Zoomcat's "servo-test-21" sketch (available in a number of places including http://arduino.cc/forum/index.php/topic,21912.msg163771.html#msg163771), I was able to enter many different angles and the servo would seem to go there OK, though the higher the number (closer to 180), the less accurate it visually appeared based on where 0 was.  What I found repeatedly, again with both servos of the same make and model, was that I could go to 156 degree smoothly and without issue, but entering 157 or 158 degrees, the servo would jump all the way to what looks like just beyond 180, and then vibrate like it was trying to move further or just confused.

Entering a number less than 156, the servo would immediately go there and be happy.  This continues to happen with both motors at any degree specification above 156.

Has anyone else seen this behavior?  Am I doing something wrong?

Thanks in advance.

Kamal
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BTW, the 5VDC supply is 3.6A - more than enough power for this little servo.

Before getting the external supply I had different issues plugging the servo directly into the 5V on the Arduino - the board got very unhappy intermittently.  After hours scratching my head about that, I got the external supply and things got much better, but the issue with the travel of the servo still plagues me.
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I'd be curious to hear any responses to this query also. I have a similar issue with the Sweep program driving a low amperage micro servo. It appears to reach the bottom end of the range fine,but doesn't get to 180 degrees before it sweeps back to the starting point. The start and end points of the sweep are consistent, but it certainly isn't making a full 180 degree rotation before reversing.
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I seem to have this issue as well. I have even went as far as placing Both hobby servos (ES08A's) side by side and controlling them both from Pin 9 at the same time. Once thing i have noticed is...After about half an Hour of playing with them and letting them run. I can now get upwards of 178 degrees outa them before the symptoms show up. If i keep them 175 degrees or less... everything seems to be okay. I'm going to leave them alone a while and let them...Cool off... and see if i have the same thing happen all over again when i start playing with them again.
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Could be some type of issue with the internal pot, which are generally very simple/inexpensive hardware wise. Exercising the pot in the suspect area might clean off dust or something else on the contact rubbing surface. Squirting the pot with contact cleaner and then exercising it might get better results.
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