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Topic: SG90 Servo Difficulties (Read 8310 times) previous topic - next topic

Bajdi

Well I'm afraid you have a broken servo... There is probably something wrong with the pot or the wiring from the pot to the little controller board in the servo.
www.bajdi.com

bloogoo


There is probably something wrong with the pot or the wiring from the pot to the little controller board in the servo.

How could I determine if there's an issue with the controller board itself? I've detached and reattached the pot to the board, and I know it's a good connection. Also, the pot is working well.

Robin2

The simplest test is almost certainly to buy another cheap servo and DON'T TAMPER WITH IT! If that works as expected it's a fair bet that the first servo is broken.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

bloogoo


The simplest test is almost certainly to buy another cheap servo and DON'T TAMPER WITH IT! If that works as expected it's a fair bet that the first servo is broken.

Let's go with the assumption that this servo is broken, because my other servo works fine. Is there anything I can do to fix it, or determine exactly where the issue is?

zoomkat

#19
Jun 06, 2013, 12:59 am Last Edit: Jun 06, 2013, 01:04 am by zoomkat Reason: 1
Quote
Let's go with the assumption that this servo is broken, because my other servo works fine. Is there anything I can do to fix it, or determine exactly where the issue is?


If your servo is spinning around like a continuous rotation, then two possible things may have happened. First most hobby servos have some type of travel stop to limit the rotation of the servo horn shaft. Your servo appears to not have one. Second, the servo pot must be attached to the servo horn shaft so that the pot rotates with the servo horn shaft. It appears the pot in your servo is either detached from the servo horn, or the pot has been damaged in some way. Below is a typical servo pix.

Google forum search: Use Google Search box in upper right side of this page.
Why I like my 2005 Rio Yellow Honda S2000  https://www.youtube.com/watch?v=pWjMvrkUqX0

bloogoo

#20
Jun 06, 2013, 04:04 am Last Edit: Jun 06, 2013, 04:09 am by bloogoo Reason: 1

Your servo appears to not have one.

Mine had one - it's one of the things that stop the servo from rotating past the 180 point. I removed it before starting this thread, hoping that the stop was the cause of my problem.


It appears the pot in your servo is either detached from the servo horn, or the pot has been damaged in some way.

I have attached pictures of one horn to show that the pot rotates with it, the movement is smooth and clean. I have also measured the resistance of the pot, and it seems fine (approx. 3.35kohm).

If I take off the metal "V", there will be no stop for the pot, and it should be able to rotate freely. How will this help the pot from locating different positions throughout its rotation?

zoomkat

Quote
If I take off the metal "V", there will be no stop for the pot, and it should be able to rotate freely. How will this help the pot from locating different positions throughout its rotation?


In a normal servo, the pot shaft rotates ~180 deg with the output gear. In a servo modified for continuous rotation (like the one modified in the picture I posted), the pot shaft does not rotate with the output gear. You can test your pot by sending your servo a 90 deg position command from the serial monitor, then slowly rotate the pot from 0 deg to 180 deg. The motor should change rotation direction as the pot cross the 90 deg position.
Google forum search: Use Google Search box in upper right side of this page.
Why I like my 2005 Rio Yellow Honda S2000  https://www.youtube.com/watch?v=pWjMvrkUqX0

bloogoo


You can test your pot by sending your servo a 90 deg position command from the serial monitor, then slowly rotate the pot from 0 deg to 180 deg. The motor should change rotation direction as the pot cross the 90 deg position.

I tried this, and it didn't work. I did, however, rebuild the potentiometer and checked its resistance once more. This time, it was measured as 5.2kohm. When I rebuilt the servo and I ran the sweep program, it worked perfectly.

AmmAr_KHalil

Hi
my SG-90 is completely jammed. Is it broken or any solution is possible?

Robin2

my SG-90 is completely jammed. Is it broken or any solution is possible?
Disconnect the servo from everything and see if you can't move the arm with your fingers (be gentle - but not too gentle) I would try taking apart to see if you can reassemble it with the gears positioned so it can move manually. Google shoud find plenty of examples of the insides of servos.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

AmmAr_KHalil

Thank you for your reply,
i've tried hard to rotate it with my hand but still did not moved.

A.

AWOL

Cross-post.
Thread locked.

Replies to here please.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

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