Hello,
I have had a total of four HS-645MG servos overheat; each one broke and was rendered useless. I have come to the assumption that, because multiple servos have broken, it must be something with my setup. I have attached a picture of my wiring. I checked the power my servos are receiving, it is 6.52 Volts.
It may also be my code. Can you take a look at it and ensure that I am commanding it correctly and not ‘over stimulating,’ over moving, or overstretching its limits? The code can be found here: github.com/crcali/BrainBot/blob/master/BrainBotTestCode.py.
Do you have an explanation as to why my servos are malfunctioning and overheating? If my voltage is too high, how do I change it? I am using the battery that RobotShop recommended.
It seems your picture is now showing up. You can edit your post and attach it using the Attachments bar in Full editor mode (see the attached image below for details).
Also, pictures of your robot and where the HS-645MG is place would be helpful. Please also include some details about how they were used and damaged, such as:
]An estimate of the amount of torque they are providing/:m] ]How long were they holding a position under load before damage/:m] ]How often did you let them cool down between uses/:m] ]etc./:m]
The more details you provide the better for understanding the situation. You may also want to upload one or more videos (< 20 MB if uploaded to your post) to show what the motions of your robot are.
As for voltage, if you are using a 6 V DC NiMH battery pack, then there is no voltage issue. Damage to motors in such a case (with the details you currently provided) is almost always due to the torque demand being too high or sustained for too long.
Hello,
I have attached an image of my wiring and servos. The servos circled in purple are the servos that are malfunctioning.
One began overheating after 15 minutes or so of use. After cooling them down and using them later that night, the other servo began overheating after 20 minutes or so of use. They were simply maintaining a position and I was sending commands to the SC-322 to make it walk.
Usually, I use them for about a half an hour, then turn them off, and use them 2-3 hours later.
Attached is a link of a video I took a while ago when I was just testing the servos, but the video demonstrates the position I attempt to keep the servos in so the robot can stay upright.
I am not home right now, but when I get home I will record a video of how I am currently operating my robot.
Thanks again,
Christopher
Here is a video of my robot moving. Although it is not what I was doing when they overheating, the position that they are in is where I keep them when the servos are waiting for anther command. drive.google.com/open?id=1JgDhWfa-4SZARK3NrEKYi7wRHWnlOH0B
(sorry it is a link; when I tried to upload a video it told me that it was too large) Image of wiring .pdf (5.52 MB)
Thank you for the detailed update. Here are our thoughts on this situation:
Wiring seems good. It is not visible in the picture, but I assume the VL wires are going to a 9 V DC battery?
Please note that 15-20 minutes of continuous use under load sounds about right for a hobbyist-grade RC servomotor. Of course, this depends on the load the motor is under / the torque it is providing.
Are you always testing your gaits on top of the surface seen in the video? If so, we strongly recommend you move your testing to a flat, hard surface (and not cloth), as this can increase the amount of torque required (such as seen in the beginning of the video, when the front right leg is pushing against the cloth, trying to “get out of it”).
It should also be noted that depending on how you programmed your gait, it is possible that you are performing motions that are not efficient and pressing too hard against the “ground”, which could very easily lead to motors overheating quickly. Since you mention the motors overheating within 15-20 minutes of continuous use, it is quite possible that is what is happening. Please note these RC servomotors are originally not meant for robotic uses and therefore need to be cooled properly between uses (and, of course, not allowed to overheat / damage themselves).
No problem. The limit on the forum for attachments is 20 MB. It is easy to go over that limit with videos, so a google drive link is fine!
I have taken a video of my lastest movements; this demonstrates what caused the Servos to overheat. As you will see from the video, there is one missing Servo, so it is not clearly fully functional. You will also hear a high pitched hum; this is from the new, very high torque Servo I purchased and I am using.
The video will most likely not reveal anything new, and I agree that the overheating is likely due to a high torque requirement.
I went to a hobby shop today and asked them about what they recommend. They assessed my situation and also told me that I am overusing the Servo and required too much torque. They recommended that I purchase a high torque servo that will better fit the quadruped. As I stated previously, there is a high pitched hum in the video; this is from that new high torque servo that the hobby shop recommended.
I have only purchased one, but I am considering purchasing three more to place on the middle leg Servo (this is the Servo that is most heavily used and is holding the most weight). The Servo that I purchased is the HS-5585MH5. Do you also recommend that I use the more powerful Servo? I want to continue using my quadruped in my current manner as it has a specific purpose and the quadruped may need to stand upright for extended periods of time and be able to move forward periodically.
I am planning on contacting customer service and requesting a refund for the four Servos that do not function as expected and sending those back.
The torque requirement is a combination of the load on the motor due to the mass of all the parts and also the wait the gait is performed. Therefore, if you continue as is, you will most likely need more torque, yes.
Usually, most DC motors (such as the ones used inside RC servomotors) can support about 20-30% of their stall torque continuously (rule of thumb / approximation). Therefore, if the HS-645MG RB-Hit-29] met your requirements torque-wise (i.e.: it is able to easily move the load required) then something with more capacity will most likely do much better for your use case (extended periods of time). Therefore, something along the lines of two to four times the torque capacity should work for your project. The HS-5585MH RB-Hit-120] has a stall torque of 17 kg-cm (as opposed to 9.6 kg-cm for your previous motor), which is nearly double. If this is not enough torque, we do have other, more powerful RC servomotors, such as RB-Hit-151 (25 kg-cm), (29 kg-cm) and RB-Hit-91 (38 kg-cm). Just make sure their size fits with your existing setup, as they may vary a bit in width/length/etc.
Well, to be honest, the servos most likely did perform according to their specifications and you did mention you are most likely using them well above those. See our notes above concerning torque.
