Servo keeps burning out - Page 1
Forum section: electronics / beginners

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 26, 2019, 08:23:02 pm
content: Hello i have a problem with one particular servo that keeps burning out. I have 6 Servos driving a robotic arm (2 on the base , 1 for the elbow joint , 1 for the wrist movement , 1 for the wrist rotation and finally one for driving the claw mechanism. Problem is the one that keeps burning is the one that drives the claw. All other servos are working fine. The base ones carry the most load and the one that burns out does so while its not even moving or carrying load.The servos are the cheap MG996R's and the IC that releases the smoke is an APM4953http://www.artschip.com/pdf/APM4953.pdfThe writing of the second chip that burned on the board is not readable.Is this a problem with the power supply ?

author: Benta
author_rank: Super Contributor
timestamp: January 26, 2019, 09:00:41 pm
content: Quote from: ChrisGreece52 on January 26, 2019, 08:23:02 pmCould be. You haven't mentioned in one word what the power supply is.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 26, 2019, 09:06:37 pm
content: Oh sorry i was writing the thing in a hurry its my thesis project and i will showcase it on Monday... problem is the servo just burned out and i have one replacement.I use a laptop power supply which outputs 18.5 V at 3.5 A then i have three voltage regulators connected in parallel everything grounded together. One outputs 5 V for the logic circuitry , the second 12 V to run the stepper motor and the third 6 V for the servos (they can handle up to 7.2 V as their datasheet states)

author: Andy Watson
author_rank: Super Contributor
timestamp: January 26, 2019, 09:42:09 pm
content: How does the claw work? Of all the motions that you mentioned it is the only one that is naturally limited. Are you asking the claw servo to go somewhere where it cannot get? If so, it's going to try to full-torque/force as soon as it hits its limit.

author: Ian.M
author_rank: Super Contributor
timestamp: January 26, 2019, 09:45:47 pm
content: If the claw servo is the only one that repeatedly fails, and they are all the same type and on the same 6V supply, it cant be the PSU. However, check the ground to the claw servo, I bet it doesn't like having +6V applied with the control signal low and a missing ground.Otherwise, IMHO the most likely explanation is its overloaded, probably because its commanded resting position is outside of the mechanical limits imposed by the claw mechanism travel.Edit: Andy shares my opinion and posted while I was replying.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: January 26, 2019, 09:55:20 pm
content: The range of motion i have it running is between 0-180 degrees. I now changed it to 15-165 so i am sure i am not asking the motor to move beyond it mechanical limits but still 0-180 should not cause it to burn up.Anyway upon further inspection i saw that there metal shavings from the gears on the housing indicating that the gears rubbed against each other violently.So i blame mechanical stress due to the shavings but i will check its connections to make sure it is grounded. Thank you.