What Killed this $99 Servo? A Postmortem
ฝัง
- เผยแพร่เมื่อ 7 พ.ค. 2024
- The $99 Chinese StepperOnline 180W servo I showed in a previous video for use on my Lathe Electronic Leadscrew died recently. Today we're going to figure out what caused the failure and get the ELS back up and running. So I can use my lathe again.
The servo:
*This site contains affiliate links for which I may be compensated
NEMA23 180W 3000RPM Easy Servo (StepperOnline*): bit.ly/37SctTB
Tools used in this video:
*This site contains affiliate links for which I may be compensated
Bondhus Metric Hex Key Set (Amazon*): amzn.to/3eqZzwb
Bondhus SAE Hex Key Set (Amazon*): amzn.to/3h9bJLZ
Starrett Precision Screwdriver Set (Amazon*): amzn.to/35taFJc
Rigol DP832 Triple-Output Power Supply (Amazon*): amzn.to/2FHtSfz
EEVBLOG Brymen BM235 Multimeter (Amazon*): amzn.to/2YKFSEk
DER EE DE-5000 LCR Meter (Amazon*): amzn.to/3ip3IT1
FLIR ONE Prot LT Thermal Camera (Amazon*): amzn.to/39ZGONa
Sharpie Magnum Marker (Amazon*): amzn.to/3mfgyIe
Mitutoyo Thread Pitch Gauge - SAE and Metric (Amazon*): amzn.to/3y4nFGC
Raw Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 3.0 License
creativecommons.org/licenses/b...
00:00 Intro
00:46 Testing
01:52 Testing the power supply voltage
02:49 Pulling the suspect servo
03:31 Bench testing the suspect servo
04:28 Disassembly
06:51 Visual Inspection
10:35 Electrical testing
14:02 FLIR thermal camera inspection
15:23 A suitable replacement
16:58 Programming the new servo
17:51 Installation
18:43 Testing
20:04 Conclusion
Do you have a lot of electronics background? As an EE of many years, I think you did a great job of explaining that whole process and identifying the operation of the various circuitry. Awesome job!
And I think you made the right move buying the same motor again, at that price point it would be silly to re-engineer it.
I agree with Stu completely and in both respects.
...and another point is spare part if somethin else fails in it...
unless its the same chip ofc.
"buy cheap, buy twice" ... in this case let's wait for part three ...
Jokes beside, nobody can tell if the expensive branded option would also have failed. Because of the circumstances that lead to this failure ... like over-voltage, shocks or the usual "produced on a Monday-product" ( hehe ). But all this is speculation and only one kind of person can exactly know what is the right thing to do: TH-cam commentators ... :P
But what you CAN say is that the brand-manufacturer provides guarantees. F.E. exchange in-between 2 or 5 years, or lifetime; Customer support and possibly help with the design of your contraption if some hurdles occur. You just have to RTFM!:) I don't see any reason to hold court about Clough42's decision to go for the cheaper exchange part. One way may be as good as the other. But one thing he said in the video made me think: that it is practical now, that he can just exchange the motor and has nothing new to adjust. Branded and certified products (this is why we in the industry use them ... and also to not land behind bars ... **g** ) guarantee a time-span when they are produced and can be supplied[1]. This is also guaranteed for spare parts and software for such systems, which are often modular and extensible. My opinion to the question if that was a good choice: It depends ... and you do you!:)
[1] Edit and Example: For example and out of the field, the not so cheap motor and motor driver parts including all connection systems and cabinet parts from Siemens come with extensive personal advice and guarantees on availability and service. Some parts will be in stock for 20 years, some are even guaranteed to be in stock and with maintenance support for 50 years. You will certainly look in vain for this at the "Alibaba" dealer.
Mtbf is 2 years. I can tell you from experience that the clear path would have lasted significantly longer as long as it was sized and installed correctly. Just my opinion, but decisions like that add up, and you can find yourself “going broke saving money” quickly. I watch people do it every stinking day.
@@VoteForBukele normally i would agree...but its obvious he does know a bit in electronics and is likely to solve many possible cenarios... guys like this are very valuble for any company...
If the new servo has the same PCB inside you might be able to exploit the ST-Link firmware-dump bug to extract the firmware from the new servo and flash it to a fresh microcontroller for the old servo. That's assuming the microcontroller's read protection is actually enabled; if not it's even easier to dump the firmware.
Had the same idea... I definitely would try it.
I was curious if something like this was even possible considering he had a "copy" in the new version.
Thanks
How can one typically extract firmware from an existing STM32? What kind of interface or dongle is needed to connect the the chip's pins to the computer?
@@pitot1988 I haven't specifically looked into this board but one thing I'd suggest researching is search for UART. It seems to be a serial connection and programming standard interface. The other you could try was searching for JTAG.
@@pitot1988 you could likely do it right through the programming header on the board, if there's no protection enabled, dumping the ROM is pretty straightforward, I'm sure someone has a video about the process here somewhere.
I think you did the right thing, hopefully this servo will work just fine. I'm saying it because I recently finished building your ELS for my lathe and I used the same servo. Hope you are reading this comment, I cannot thank you enough for your brilliant design and fantastic videos that guided me through the entire build process.
There are usually some internal regulators inside the microcontroller, outputting internal core voltages onto lowish value ceramic bypass caps near the micro. Those multilayer ceramics are some of the most common things to fail - they can crack when the board flexes or vibrates. If one of those caps is shorted, I'd expect the regulator in the micro to get hot. You might be able to identify the culprit with a multimeter, or by just pulling the bypass caps off one by one.
That sounds like a reasonable possibility. A servo is certainly something that can have some vibration, especially mounted on a large vibrating machine. I don't know how much the boards would flex, they looked reasonably well mounted. But it is certainly a possibility. The interesting question is whether the microcontroller would have survived after the internal heating.
An ohmmeter with Kelvin connections might get you into the ballpark.
The hard part with those ceramics is that if they're broken, it's basically impossible to know the value without the schematic.
@@Teklectic Could remove two, the bad one and a good one, then measure the good one with a capacitance meter.
Thanks for taking the time to share this. Are you considering a Clough42 redesign of the board that failed?
James. Thank you for this walk-through. Your explanations may be the only ones I can watch start to finish and truly understand the information. Have a great week sir.
You just popped up in my TH-cam feed.
Great work.
Great subject mastery.
Great video documentation.
Great honest, human communication! (Thanks for the Dentistry Lenses tip for "old man glasses!) Masterful - novices or skilled pros can't help but learn from this video, sir!
Great common problem of "buy replacement" or go through work of warranty, repair, research new source/parts - across all walks of life and lines of work. Of course your time and expertise are so obviously valuable, that the time saved in re-buying is wisest choice. Wow.!
Thanks again!
Great job putting all your tools in the description. That's hard work and dedication to a good video 👌
Getting the same servo isn't lazy... it's strategy! :D
Great content as always! Thanks again James!
So glad I stumbled upon this channel. Great stuff!
I watched this with keen interest (and was "rooting for you" through the diagnosis, hoping you'd find a simple fix) because I have the exact same servo driving your ELS on my MX-210V. Mine has been working perfectly well for about a year now; hoping for many more. Still, for $99, it's a terrific bargain -- unless these failures become a pattern. Thanks for the excellent walk through of the circuitry; very informative and entertaining.
Genius! Thank you for posting this video. I’m configuring these servos with a masso. Got the db9-usb cable from A..zon and finally have a connection. I’ll try 500 steps too as a starting point. I greatly appreciate your channel and hopefully your getting rewarded for your hard work!
thumbs up for knowing what you want, why you want it, and chasing after what you want., even in a failure, you're making it a win teaching us doubt it. thanks
Always pros and cons, you made the correct choice. Great video.
Love ur diagnosis method, very methodical, logical and we'll thought out
James I’d say it was a good idea to go with an even exchange. Now with that said, if this one craps out in a year or two, it might be worth stepping up (pun intended! 😂) to a more reliable long term solution. Thanks for the video. They are always a pleasure to watch.
These servos are typically great but i would’ve thought a 300w model would’ve been more appropriate for his application.
great content man, love how diverse your machining videos are.
I think you took the correct path, I personally do something similar with my projects.
Keep up the good work.
Hi James, useful walk through to show how to diagnose the problem. Thank you for spending your hard earned money to let us know if it is a generic fault! I've still got your wonderful ELS on a breadboard ...... one day, one day.
James, I love the diagnostics that I will never understand but understand enough to say that replacement of the component was perfect. no parts cannon here.
This is just awesome Sir. I've learn so much just by viewing this video. Thank you for sharing
That was an interesting postmortem, and well explained. I liked the idea of using the thermal camera.
A gremlin let the magic smoke out of that servo. I can honestly say that I have done the same, bought the same thing that betrayed me and sometimes it betrayed me again. Thanks for the video keep on keeping on.
Damn Son! You really do have all the toys.
I think you're an underrated channel here on the TH-cams, James.
Keep up the fine work Mr.
Thank you for sharing this video, you did the right choice to save time & effort, wish you good luck.
James you did the right thing nicely done!
Nice troubleshooting, satisfying to see a pro at work
Appreciate this update!
I enjoyed the diagnostic walkthrough, encourages me to do more digging on complex devices needing fixing :-)
good job and great explanation of what's going on.
I consider myself pretty good at a lot of things but I bow to you without any hesitation.
I enjoyed your explanations of everything. The component identification was great. I’ve tried watching other videos on electronic components, but they don’t have the entertainment flare you’ve got. And I wouldn’t say it’s dumb to buy the exact component that failed the first time around. If it craps out in a similar fashion as the first- “Huston, we’ve got a problem.”
Hi James, I thought it was a good idea to replace the servo with the same type as you will have an opportunity to extract the firmware from STM32 on the new servo. Could be the making of another great video for the future. Never a bad idea to replace a part with a known good one. I know lots of mechanics that do that very thing each and every day. Thanks again for all your efforts in producing great videos.
I think you did the right thing. It could have been a one-off failure with the device. Time will tell. Thanks for your explanation during the fault finding.
Love watching your videos, you do a great job of putting them together and are very informative. This might be an expensive request but is there any chance you could do a video comparing servo motors (not steppers). Personally I've used Clearpath motors in 2 CNC builds but I've since heard Delta servos are cheaper and better and then maybe Fuji servos?
Thank you James.
I have used about a dozen of this exact servo, we did have one break but in our case it popped one pair of mosfets on the 3 phase motor output. I simply replaced those FETs (and the fuses which blew as the rail was shorted) and the servo has worked fine since.
Remember, you now have a bunch of spare parts for the new stepper. Work that into your cost/benefit ratio.
Glad you are the kind of guy I would like to be from electronics to mechanics! Thanks
Well done, very sound knowledge of electronics as well, kudos!
I also had a problem with one of my Chinese stepper motors. For me it was a mechanical and I was able to fix it. Not before I purchased new one, but it's always good idea to have a spare if they are used in important place.
It's funny how they appeared to be relatively good quality but there is still some details which fail.
Mine stopped spinning but coils were powered and there was some sound when I drove it, though controller went immediately into error state. I suspected short circuit, but all coil resistances were OK. When I opened it up, I didn't find anything wrong but when I put it back together I realized what the problem was. Face and backplate were machined in a way they didn't lock into place. Alignment was maintained only by friction and it was big nema34 motor. It had been slipped and prevented motor from spinning.
I redesigned my mount so the motor body is supported by rubber, and it has worked well since that.
I've no idea if you've made a good decision. What I do know is you did what I would have done. Hope it works out. Thanks for all the great content.
nice analysis
The channel gets a new nick name... The Lazy Genius
We recently had an X-axis servo motor fail on a Juki Pick and Place machine in our factory. I very quickly came to the conclusion that they were not intended to ever be taken apart so instead of digging further I put it back in the machine with the power disconnected and ordered a replacement motor. After the replacement arrived I forcefully disassembled the motor and found the cause of death was a split magnet on the rotor from years of rusting and expanding until there was nowhere left for it to expand. The moisture must have gotten into there during manufacturing as the motors are entirely sealed from the outside world.
I built the ELS about 1 year ago and love it , no more gear changing , I was wondering if you had any plans to add any features to the firmware, such as automatic stop and start and return to the tap cycle Just a thought Thanks for the great projects looking forward to the future
Thanks James.
One thing, you always discharge capacitors before connecting an LCR meter.
Spend hours reconfiguing a new servo or $99.00 for the same one that fits. I'd do the same thing too, your time is money too. Now if it fails again then all bets are off as to if I'd take the time to reconfigure... I'd say you chose wisely. Oh, you forgot one tool in your list of tools used, like you my eyesight isn't what it used to be and I'd like to try the magnifier you used. Thanks for another great video James!
Thanks.
The smart thing to do is to do what works best for you.
Leadshine was the company that ripped off the stepper drive design from Gecko years ago. They sold them so cheap that Gecko developed an improved design that used programmable chips to slow down the Pirates.
I wouldn't be surprised if your servo drive was also stolen. That's the world we live in and the Chinese have different ethics than we're used to.
You may try and contact them to see if you can buy the replacement board without the motor to save a few pennies on a backup motor.
Dead on with the Chinese ethic on IP. Looks like a logical reason to stay with a replaceable controller but at $100 a copy it may not be worth it.
Hi James - I’m very interested in knowing more about the dental glasses. Source? Cost? Would you recommend them? Pros? Cons? Optical clarity?
FWIW, please do a video on the glasses. There are a bunch of us old guys out here, and not much info in YT machinist land for vision aids. OptoVisors work only up to a point.
I'm not old, i'm only 40, but i need all the vision help i can get as well!
+1. Looked for this comment to see if there was anyone else who is also old and blind. I tried one cheap rando dental loupe from Amazon and it was useless rubbish. I know some must be better than others, but I aborted my search.
I'd like to see a link for the dental loop glasses too.
I’m also interested in these. Can you provide a link for them?
+1. I d like to know about them , too. Real dental magnifiers are screamingly expesive though. I m hoping this has a more reasonable price tag.
If you go to the settings in the FLIR software, you can adjust and remove the paralax issue.
Im still using my itty bitty dual flexi extruder on my makerfarm I3v. Im a big fan of your work.
Have you thought about driving the speed of the spindle based on tool offset and position? So you can get a constant, or near constant FPM?
I think you made the right decision. Now, if it fails again in a short amount a time outside the warranty, time to change.
Nice video, you did the right choice. Are there any plans for upgrading the ELS, ex. Saving the settings in eeprom, so it's kept for power up.
Good choice, but maybe you should have bought two so you have a ready spare. And in refitting, I would definitely have turned that printed bracket over so it can pull back straight again. As for fault finding with a thermal imager, that was a game-changer when it became available. If you have time, save the thermal image of a good working unit for comparison when there is a failure.
Good to see you also have one of Dave's Multi metres.
You could read the flash to extract the binary file from the new motor's STM32and then replace the uC on the old motor, to then program the new uC.Will cost you a second servo anyway, but you'll have a replacement, at least.
Yes, I was looking at that debug connector on the main board.
Never hurts to have a backup.
Possibly... most likely scenario is that the flash read back lock bit is set. There are ways around this but takes time and energy.
Highly unlikely that the micro is unlocked for reads, but worth a try as the STlink is such an inexpensive programmer/debugger.
STM32C031C6T6 actually possible to buy one of these, ST Micro's parts have been out of stock for ages due to supply chain and stupid management issues.
Your explanations are great. (Of course it all went over my eighty year old head) But, I sure enjoyed watching. And, I did learn a little.
I LOL'd at you shaking your finger at the lathe door :). Based upon your Clearpath review and my own research, I bit the bullet and bought them for my future CNC router. What decided it for me wasn't so much the hardware, but the apps. The thought of buying something needing sw configuration from China just seemed ripe for disappointment.
Sorry to hear about the stepper killer- killer trouble but I'm glad it was solved relatively inexpensively. Have you looked any more into the lcd screen upgrade?
Interesting seeing you attempt to diagnose and fix that servo. I work in a motor repair shop and my specialty is servos but I would never get one of this type across my desk. Considering tech labor runs in the ballpark of 100-150 an hour it would never be cost effective to repair one that inexpensive and available. Generally if its under a grand and the shop manager lets it through the doors at all its give it a quick inspection to see if its something quick to fix and if not quote a replacement
I love the electronic autopsy!
I don't blame you for getting the same servo one bit. Screwing around and having to reconfigure your setup to swap in a different motor is a huge pain in the arse, you might as well keep it simple. Hopefully this one will last longer for you! 🤞 If not then I would consider switching servos so you're not having to spend money every year or so for a new one. 👍👍
Great Video
Your teardown was great- however the unprotected pins and lack of water/oil/swarf resistance wouild make me go for the Clearpath, hands down. I can't believe that wasn't full of chips and muck, there are no spots behind my lathe that don't get covered with oil droplets and metal dust.
I too have this same servo and all the components to build an ELS, I simply have not had the time to put it all together yet. I hope this new motor lasts longer than a couple years as well. Have you considered adding stops to the ELS to make threading to a shoulder easier?
Some micros have a boot from external memory option set by pullups/down during reset. If so a change of micro may be possible. Some other good suggestions in the comments (reg caps) . Great teardown. love the encoder/active leadscrew.
If it ain't broke don't try to fi... oh wait. I can't blame ya for replacing it with the same motor, I mean for only $100, I would have done the same thing. I really appreciate how you did a walk through of the electronics on the boards and showed how you troubleshoot the issue. The thermo-camera was a nice touch. Although, I'm a little disappointed you went through all the trouble and didn't take the time to sharpen your pencil. Come'on James! j/k 😂😋👍 I always appreciate your videos, definitely looking forward to the next one.
awesome video! you can change the microcontroller and replace the firmware with simplefoc
FYI, some Leadshine resellers or volume users can obtain new spare parts for the motors including the PCBs. I have replaced some of their encoder/hall sensors before now on their regular servos.
This was the comment I was looking for. Contact Leadshine and send a link to your video. Tell them you will do a video of the repair when they sell you the spare PCB or Microcontroller.
This video exceeded my expectations.
I would check the input signal voltage under every circumstace just to be sure there are no voltage surges happening. Something must have destroyed the chip. Sometimes its bad board design, but its best to be sure its not your input that destroys the chip over time.
Very interesting those thermal cameras, ive seen some good analysis done with these.
Greetings,
Jeff
That's a strange fault James. I would have popped the 3v3 regulator off or isolated the output. Perhaps the under voltage is causing the stm32 heating - unlikely as they do work from 1.8 upwards but it would have been worth double checking. I've had stm32 fail in particular under voltage conditions. Could be caps around the 32 as well I suppose. Cheers.
When dealing with electronically populated PCBs by using a pencil around the circuit (CCt) you can place carbon particles on the PCB which can cause short CCts in the most extreme case
If the new servo's microcontroller doesn't have an internal security fuse (or if it does and the fuse hasn't been burned) you could extract the firmware and possibly repair your dud. You just have to decide whether it's worth going down that rabbit hole for a $100 item. At those prices a one for one swap seems like a wise move. If you find yourself faced with having decide whether to buy a third one at some point, then go for a higher quality one. My $0.02.
Good choice. Nice troubleshooting.😊😊😊
With a little legwork you could probably source a replacement board; giving you a spare servo for the shelf.
Great video! Have you considered extracting the STM32 firmware from the new one and then writing it to a new STM32 and replacing it on the broken one? That way you could have two working units.
So how do you find those glasses, I have been looking at the same thing that is popping up on my FB all the time. Im in New Zealand so by the time I get it here its not as cheap as I suspect it would be in the US so Im a little hesitant having been bitten by some previous adjustable glass's I purchased that were useless. I do like the look of these and I assume I can fit them onto my prescription glass's and they dont fall off etc. Any suggestions/recomendations
You were correct to replace with the same, stm32 blowing seems a random failure, unless there is back emf appearing, very unlikely with what looks like optical isolators before the power electronics… would have been interesting just to break the power supply to the microcontroller and see if the psu and regulator recovered to 3.3v more out of interest then anything else.
The opto is between the STM32 and the outside world. But the stm32 is not isolated from the drive circuitry or the motor.
Great Video! I only wonder about two things. How many hours were on the servo before it gave up? What is the root cause of the failure? i.e. ESD, over voltage....
The part of this that really surprises me is that you were able to obtain the exact equivalent, 2 years down the road. I doubt you will be able to do that in another 2 years time. It's possible that the 'upgraded' model available then will be close enough in format and specs that you could fit it, if you are lucky. I think in your shoes I might buy another one now, whilst they are still available. I understand you would probably want a different model if this one fails again, but that's a lengthy project and will leave you without a lathe for a couple of weeks at least. With a spare, you could be up and running in 5 minutes, giving you time to implement a different servo/stepper installation. Not much more than the cost of a set of Starrett screwdrivers.
The design of the power circuit for the processer was fine and the caps were good so I think you just had a unfortunate processor failure. If it happens twice of course, time to upgrade, as logic dictates. You don't need captain obvious then 😊. I'm new to your Chanel and I must say, what a elegant solution you created. Having rotation speed feedback, nicely done. I am an admirer.
one major advantage is you can find spares for future use form the old servo
You are clever, nae brilliant on many levels.
great in depth look! It really hurts having to bin an entire servo just because of a 3$ IC. Even reselling for parts wouldnt be economically viable. We should require for stuff to be easily repairable. Manufacturers should provide firmware blobs at least, so one can just replace and flash a new IC without the whole thing go to waste.
Whhen dealing with power circuits from a random chinese manufacturer, I usually swapped the power related capacitors with Japan made capacitors, that usually helps prolong the device and made it run cooler...
I have bought one of these electronically screws from you and it is absolutely fantastic. I built it into my mini lathe. I printed a plastic 3-D enclosure for the main circuit board and put that in the enclosure where the changed gears used to be and the belts are still located. I have also bought one of these built-in stepper motor and driver seems to be okay at the moment. Initially I had some problem with interference. But the development board was not earthed to the main chassis of the lathe. Switched mode power supply and I suspect coupling capacitors caused the potential of this board to fluctuate. As there are Opto couplers everywhere. As soon as I earthed the board to the lathe all problems went away..
I noticed there were several SMD caps around the microcontroller. These have a habit of failing short. Given the heat your seeing on the micro i would guess one of the caps had gone short. I would test each one for short.
Hi, great vid. Would you please be so kind as to publish the urll for those magnifying specs. Thanks
I kind of expect a video in about two years, introducing the "Stepper Killer Killer Killer".
Since when do ST's go bad? I'd say it was a safe bet to buy the same. I'm glad you took out the thermal camera, you watch Northridge Fix too?
Your a genius!
A man after my own heart. Skip the schematic - this stuff is all the same, just dive in and a bit of logic, problem solved. You and me are the people everyone needs the day the SHTF. Great presentation sir. I was thoroughly entertained.
If it's not broken, don't fix it. If this one drops you can upgrade. With the way tech goes it'll probably be smaller and have more power by the time that one farts and let's the smoke out.
Any chance the servo was getting a bit too much heat from the main motor of the lathe? Seeing the servo next to the cooling fins.of the main motor (despite the airflow) made me a bit curious if that helped with the early death
For your ELS project, any thoughts on pro/con (if it's even possible) of using an integrated stepper/driver motor?
Is it possible to cut rifling using the electronic lead screw? I collect and shoot antique firearms. Every now and then i have to put a barrel liner in a gun. Colts originally had Progressive rifling. so it would start off straight and then progressively add more and more twist. I would love to be able to replicate this rifling. How difficult do you think this would be using electronic lead screw?
Not having to go through reprogramming is a good thing. James - Can you put up a link for those "cheaters"? Something that works at those distances would be great for my 68 year old vision!