Quadcopter motor twitching. What next? | BAD MOTOR OR ESC TROUBLESHOOTING GUIDE
So what now im joshua, bardwell and youre gon na learn something today well, the very first thing were gon na. Do when weve got a bad motor or esc or anytime were troubleshooting on the bench is were gon na take off our props, never have your battery plugged in and your props on on the bench at the same time. Well, if youre using a smoke stopper, maybe you could get away with it, but were gon na need to spin these motors to test them and a smoke stopper wouldnt. Let us do that so props off for safety. Now that the props are off. How do we know that the motor or esc is broken, and the number one symptom that youre going to see is that when you arm the quad and try to spin the motor it twitches instead of spinning now you cant see this, but i can also feel That when i spin the motor theres a lot of resistance there, let me see if i can demonstrate that, for you here is a good motor and you can see bearing doesnt sound real great, but the motor spins pretty normally. But this motor, which we suspect to be bad, if i try to spin it Music, you can see it. It just will not spin its really bound up when we have a situation like this, where a motor twitches but does not spin, it almost always points towards the esc, the motor uh or the wiring in between them, but not the flight controller.
Why not? The flight controller, because a flight controller, all it does, is it tells the esc how fast the motor should be spinning and then its up to the esc to actually make the motor spin that fast. So you could imagine a situation where your idle percent in beta flight was too low, especially if you had a really big heavy motor that needed a higher idle speed to get it going. And when the flight controller said to the esc, lets get the motor going. That value that throttle value that the flight controller was sending was too low and the motor didnt start spinning. But what you would see there was kind of a push pushed pushed like like when you raised the throttle, slider uh in the betaflight motors tab, and you wouldnt see that kind of tick, tick, tick, tick, tick, tick, tick, tick, tick like were seeing here, so the Twitching motor that were having is either related to the motor, the wiring to the esc or the esc itself. And you might think that the fact that the motor is physically bound up its dragging would immediately point to the motor itself as the problem and youre right. But not 100 of the time. Yes, a mechanical problem with the motor like a damaged bearing or a bent shaft thats, allowing the motor bell to rub on the magnets could cause the motor to drag but im going to bring in this perfectly good rcn power motor to demonstrate that there are also Electrical things that can cause the motor to drag, and so, if i just take the motor and spin it it just spins normally, but if i take two of the motor wires and touch them together and short circuit them to each other.
Well, youll have to take my word for it. You can do this test yourself. There is more drag on the motor and the motor will slow down faster and the reasons for that are outside the scope of this video. But suffice it to say that if you have an esc that has a shorted out fet, it can cause those motor wires to be shorted together inside the esc and that can also cause motor drag and theres. A difference in feel between mechanical drag and electrical drag. So were going to start our troubleshoot with a physical inspection of this motor and were just going to look and see if we can find any defects. And the first thing im going to do is im going to look at the motor edge on and im going to rotate the motor bell and im going to look at this gap right here between the motor uh bell, the bottom of the bell and the arm Or maybe the gap between the base and the bell, but im gon na eyeball, a gap like that and im gon na just rotate it and im going to see. If that gap changes size, you could even use a caliper or a feeler of some kind to measure it. But what im looking for here is whether the shaft is bent and the bell is off center and i dont see it. It looks pretty freaking square. It looks pretty dead on, i dont see any wobble there, so i dont think we have a bent motor shaft were going to go back to this rc and power motor for this next point, because we need to look up inside the motor and its not easy To see that, when its actually mounted on the quad, what i want you to see is that the motor is constructed of a steel ring which has magnets glued to it.
These are the individual magnets and then from there there are stator poles, the poles of the stator here and if the shaft is bent or if the bell is out of round, if its an oval instead of a circle, what well see is and will feel, is That, as we rotate the bell, there will be a rubbing at certain points, its usually not all the way around its usually like right here, youll feel a rub and then itll release and thats. Another thing were going to check for when were doing our physical inspection of the motor, but with this motor i dont feel any rubbing at all. It is perfectly smooth all the way around its just that there is a sort of a constant drag and heres the other interesting thing. The faster i spin, the motor, the more there is drag its almost like pulling an ore through the water. If you go slowly, theres very little drag if you go quickly, it pushes back harder, and that to me is telling me potentially that we have an electrical problem in the esc that is characteristic of that type of electronic drag, as opposed to a mechanical problem with The motor but lets proceed with the troubleshoot and see where it goes. Another check is to look at the windings here from the top and see if there is any sign of damage specifically looking for discoloration or burned spots. Sometimes you can also smell it.
If you literally put your nose up to the wine, you can smell the burned enamel. I have had cases where i slightly smoked a motor, but then the motor continued to work. Fine, i didnt burn all the way through the enamel and the motor was still functional in general, though, if youve got a case where a motor doesnt spin – and there is any sign of damage to the windings, discoloration or or black scorched spots, thats a sure sign That the motor is just cooked and you just need to replace it. The other mechanical check that i like to do on a motor is to check for vertical play, and what im going to do is im just going to push or pull up and down on the motor and feel how much vertical play there is in the shaft And this motor has like literally none you cant, see and i cant feel any movement. There could be as much as maybe a half a millimeter of vertical play and, like some motors, like the iflight motors, have a little bushing inside the motor as a shock absorbing so you may get a small amount of vertical play depending on the motors construction and How tight the motor screw is on the bottom, but if youve got a motor with more than about maybe half a millimeter of vertical play. That may not cause the motor to refuse to spin, but it certainly isnt helping your gyro, and it could indicate that the motor has been subject to enough damage that hes replacing anytime youre dealing with a bad motor or bad esc.
Youre always going to want to have one of these, and this is a v fly short saver and its like an electronic circuit breaker when theres over current. It will trip and cut off the circuit and prevent damage except a circuit breaker. Does it trips way faster than a circuit breaker like in sub millisecond time, hopefully before any damage can be done? The v flash short saver is the one that i think is the best ill put a link in the video description. If you want to pick it up, there are other ones out there smoke, stoppers and so forth. They all are fine, but this is the one that i like to use so were going to plug a battery into the smoke stopper or short saver, and then this option here, the blue light means were on a 2 amp setting. The no blue light means were on a one amp setting. I always like to start on one amp, because you want the lowest trip point as possible, that will minimize the odds of damage were going to plug in here and then were going to power up the quad. Now the v fly short saver has an on off switch, which im going to use to power the quad up and down. If you dont have that, then you can just plug in and do what im about to show you and what im going to do. Is pinch the suspect motor in my fingers and im going to power up the quad and you know how, when a quad first powers up, it goes doo, doo, doo, doo.
Well, it turns out thats the esc, maybe making those beeps and the actual speaker thats, making the sounds. Where is it wheres, the speaker thats actually making those beeps its? Actually, the motors the esc can vibrate the motor coils in such a way that it actually makes sound in fact, theres actually custom esc firmwares out there that, like literally make your escs talk or can play a sound file, but the heli doesnt do that. It just goes, do do doot, and you want to understand what those beeps mean. The doo da doot means that the esc is powered on and talking to the motor. It makes the motor beep and then the dut means that the esc has seen signal from the flight controller and is ready to spin the motor. But we cant just listen, because if weve got one good motor were going to hear those beeps from the good motor. We want to know what the bad motor is doing and thats. Why were going to pinch it in the finger and feel as well as hear the beeps? Here we go ready. Okay, one amp, didnt cut. It lets, try two amps, no its tripping again! Well, thats a shame, but its also a great demonstration, so the smoke stopper tripped on one amp and it tripped on two amps at this point. What some people would do? Go freaking, smokestopper whats your problem and they would plug in the battery and then something would smoke.
What the smokestopper is telling us is that we have a short circuit somewhere in this quad and it is protecting us from smoking. Whatever has the short circuit. So, where do we go from here? Well, the good news is that uh, this quad is the rotorite solder free build, which means it has mt30 connectors on the motors, and it is super easy to just unplug this motor or, if you didnt, have that you would desolder the motor and see if the Short circuit condition goes away anytime, you have a short circuit, you just start desoldering things and see where the short circuit is and by the fact that the short circuit goes away when you disconnect the last the thing that has it so here we are again were On one amp and weve got the motor unplugged and were going to try again, okay, well, that it started to go, but the one amp, i think was not enough. So lets go to two amps: okay, perfectly normal, so the smoke stopper tripped when we had the motor connected, but it didnt trip when we disconnected the motor and thats, certainly starting to look like we have a bad motor lets talk about motors and how they go Bad because weve identified that we dont have any obvious mechanical defect in the motor we checked the motor to see if the shaft was bent or the bell was rubbing the bearing felt okay. Everything seemed basically okay in that motor, but the electrical problems are much harder to figure out so im going to put my multimeter into continuity, check mode and thats the mode where, when theres electrical continuity between the probes, you get a beep and normally thats how you Chase down a short circuit, you test for continuity, and if there is continuity, then you have a short circuit, and that tells you where the short circuit is, but that doesnt work with brushless motors watch.
This is a perfectly good brushless motor and im going to check for continuity between the motor, pins and sure enough continuity is there, and the reason for that is that brushless motors always have electrical continuity between the motor wires. So why dont they like just short circuit and fry the minute you apply voltage to them. The answer is that the esc has the ability to control the amount of current going through the motor and when it drives the motor it just doesnt. Let a short circuit happen: why is it bad? Why is this? Why is this motor bad? Because it has a short circuit and this motor isnt bad, when it also has a short circuit. But it turns out that if there is a connection between the motor wires anywhere other than the very end of the wire, so the wires go into the windings. They wrap around the windings in a certain pattern and then in the very center the wires come together and if the motor has been damaged, for example, its been overheated and the enamel coating of the wire burns off youll get a short circuit between the two wires Between the two phases, where its not supposed to be, and then you end up in a situation like we just saw here where you have a bad motor that causes the smoke stopper to trip. But the takeaway of this situation is that you cannot use a multimeter to test for short circuits in a dc brushless motor, at least not the kind of multimeter that most of us have.
You need a very, very sensitive multimeter that can measure like down in the milliohms or you need something called an inductance or henry meter which can measure the inductance of the motor coils to tell you that its bad. Now, in this situation, we have pretty definitively identified that this is a bad motor, but i dont want to just discuss this exact situation. I want to give you tips for troubleshooting in general. What i might do next, if i wasnt sure, is, i might disconnect the motor from the esc and c if there still was that drag on the motor or, if it now spins freely. The short circuit that is causing the drag on the motor could be in the motor or it could be in the esc if we disconnect the esc and suddenly the motor spins freely that points to the esc as potentially having a blown fet. And there actually is some troubleshooting you can do with a multimeter if you have an esc that you suspect, has a blown fet im not going to go into that in this video, but ill put a link down in the video description to another video. I made that goes into that in more detail. So next thing were going to do, is were going to take this motor off and were going to swap it with a good motor and were going to see if that fixes the problem. Any time youre taking motor screws off and you have an even partially script, screw, throw it out and replace it.
Its only going to get worse from there youre going to end up with a motor you cant change, because youre stuck in the field with a stripped motor screw. So here is the esc wire, where the bad motor was were going to take the good motor and were going to plug it in there. I dont even need to mount it were going to take our battery were going to plug it in and were going to power up perfectly good. So at this point for this specific troubleshoot, we have definitively identified that this motor is bad and basically need to discard it and replace it, but were not going to stop. There, like i said, were going to continue the troubleshoot, so you could solve other problems and what i said you should do is pinch the motor and feel how many beeps there are boom and i can feel all five of those beeps. So what does that tell us when you feel the first three motor beeps boo, boo boop, that pretty much tells you that the esc is good, its, not a hundred percent, but it pretty much tells you the esc is working as it should. The esc has power and the esc is able to drive the motor poles at least a little bit if you didnt, feel those beeps or if those beeps were much weaker on one motor than on the others. Then that could potentially tell you that there was a problem with the esc or the motor, but if we feel those three beeps real strong, we can conclude that the any problems that were having are not probably not related to the esc or the motor.
The last two beeps boop boop that tells us that the esc is seeing throttle signal from the flight controller. So if we felt the first three beeps, but not the last two beeps, that might be if you didnt, select a motor protocol in betaflight betaflight ships with uh when you first flash it, the motor protocol is disabled and you need to set it to d shot. 600 d shot 300 or whatever, if youve left it undisabled youll get boo, boo boop, but you wont get boop boop. If you had some super old esc that didnt support d shot and you had your flight controller set to d shot, you could get boo boo, boop, but then not the last two, because it just doesnt understand the uh input throttle signal that its seeing the other Thing that could cause the missing last two beeps is: if there is a problem with the wires connecting the esc to the flight controller, are you kidding me right now? Hey there its joshua from the future. I know why joshuas esc is not making any sounds right. Now, hes terrified that its a bad esc and hes literally had this esc die on him in the middle of the video but thats, actually not what it is and hes just about to show you how he figures that out and what it really is. But before we do that, if youre enjoying this video, if youre learning a lot and if you think more people need to see it, would you mind going down and hitting the like button, it sure does help the analytics.
It really means a lot. Okay lets go. Watch joshua squirm. Well, what i wanted to happen was to power up the esc with the esc wire unplugged, so the flight controller was not connected and what i expected to hear was doo doo doo with no do, but instead it brings us to the next thing that you could Have get which is no beeps whatsoever if you plug in the battery and you feel or hear no beeps whatsoever. That tells you that your esc is not getting power or your esc is dead and in the case of a four in one esc, like weve got here, we get a little bit of additional troubleshooting information because we didnt hear any beeps at all, which means none Of the four, if you had a four in one esc, you could have one bad esc and three good ones, and you would still hear doo doo, doo doo. You just would have to pinch the motor to feel that one of them wasnt beeping, but in this case we have none at all, which is a beautiful opportunity to continue troubleshooting, and the first thing im going to do is just get my battery checker and see. If ive killed this battery by accident, no its at 4 volts well in theory, if the battery was dead, then we could get no beeps, although usually you would kind of hear you wouldnt get no beeps at all. Well heres! The next check that i would do.
I will plug the battery in im gon na power up im gon na have my smoke. Stopper turned on for safety im gon na get my multimeter out and im gon na check at the esc power pads that the esc is getting voltage and i dont see how it could not be. But you never know im going to be real, careful not to short circuit anything here, although i do have my smoke stopper as a safety check. How many volts have i got oh ill use the legs of the capacitor thats an easy way to do this? No! No voltage theres something wrong with my smokestopper. Is my smokestopper, not outputting voltage its not has my spokes number died, how its glass, not my esc, v fly. I vouched for you. What are you doing? I got another one i got another v fly lets check it. Okay voltage, ladies and gentlemen, 15 volt thats what we should see thats what i expected to happen. I dont know why, but my smokestopper seems to have suddenly died on me, the best possible time to demonstrate more troubleshooting opportunities um. So that was an example of three but three beeps due to dude and an example of no beeps and how to troubleshoot that, in the in the case where you get no beeps at all. The first thing i want to do is verify that the esc is getting power at all, and i do that with a multimeter.
I test with a multimeter to see whether there is voltage on the power pads uh, and in this case we saw zero volts, which told us the esc was not powering up and then i sort of chased that problem upwards from the esc to the battery right. Do i have voltage coming out of the battery? Yes, do i have voltage coming out of the smoke? Stopper! No huh! Well theres your problem. If you have voltage getting to the esc – and there is no beeps at all, the esc is dead, its just dead sucks but thats thats, the thats, the conclusion so weve discussed a damaged motor and a damaged esc. What about the situation where you have a damaged flight controller uh, and this one is frankly, more rare of the two um when flight controller, when flight controllers die, they tend to die by like the five volt regulator, dies and the whole flight controller shuts down, or The gyro goes bad, but the individual motor outputs on a flight controller are not usually the first thing to go, but lets discuss that situation anyway. What youre going to see when you have a bad motor output on a flight controller is number one. The motor wont spin at all most of the time Music youll get due to do, but not do do and that again tells you that the esc is working fine, probably, but the flight controller is not talking to the esc.
At that point, you have to decide if there is an issue with the flight controller configuration or, if theres an issue with the wiring. Now when i say issue with the wiring, what i mean is you have to literally inspect the wires? Do you just literally, have a broken wire, give a tug on the motor wires? Did you build this plug yourself and you didnt insert one of the plugs all the way and its not making contact unplug the wire and look in there at those pins? You can barely see them and see if one of those pins is bent over and not making not actually making contact, look on the esc and the flight controller and just inspect the wire. Is it pinched in a standoff and getting cut, but literally just inspect the physical connection between the esc and the flight controller? If thats not the issue, then we can think about the flight controller configuration and the first thing im going to do is i am going to look in the motors tab and if i have a quadcopter, i want to see one two, three four motor sliders there. You can get in a situation where, if you have messed up the resource assignments, if youve been trying to remap motors or if youve been playing with the mixers like youre, trying to build a hexacopter or an octocopter, but youve accidentally set the flight controller. To be a quadcopter, then you will see that theres missing motors there in the motors tab uh at that point, youve got to fix the configuration set, the mixer correctly or, if youve been playing with motor remapping and youve screwed it up.
You may need to just reset the configuration of the quad entirely default, put it back to defaults and start from scratch and thatll at least get them working again. Now, if you do discover that your flight controller has a bad motor output, there are ways you can fix it. Uh you can reassign that motor output to a different pin or pad on the flight controller. It does mean that you wont have all your motor wires in one little neat plug youre, going to need to take it out of the plug and solder it somewhere else on the flight controller. But at least you can keep the flight controller alive. Ive got a video about how to do that ill, put it down in the video description. If you want to see that tutorial on motor remapping, unfortunately, sometimes it is actually the esc. That is the thing that is dead, not the esc motor drivers, but the actual motor input signal on the esc thats. The problem. How do you tell, which is which so youve got a case where the esc is not seeing motor signal from the flight controller and youre, not sure whether the flight controllers output or the escs input is the problem? What im about to show you is a giant pain in the butt, but it is a way to answer that question and if it saves you a 60 or 70 or 80 esc itll be worth your time.
The first thing youre going to do is youre going to identify, based on the pin out diagram of your esc, which of these motor wires is the suspiciously bad one. If its motor number one two three or four youre gon na look at that pin out youre gon na identify, this is motor number four and then what youre gon na do is youre gon na remove that wire from the plug and youre going to pick any Other motor and youre going to remove it from the plug and youre going to swap them and put them back in the plug and at that point, youve swapped, the motor outputs at the esc and at that point, if the bad motor. If the motor thats, not getting those last two beeps moves, that tells you that its the flight controller, that has the problem and if it doesnt move that tells you that its the esc thats having the problem. Think that through. If you need to thats how you figure that out by the way, if youve never done this before the way to remove these, is you get like a little thin knife like a razor knife or utility knife, and you lift this little tab right here, come in From the side and lift this little tab and then just pull outwards and then what i like to do is just push down on the tab, gently and then reinsert the wire and then thats how you thats, how you switch them, make sure you put those wires Back in right side up, they can go in upside down.
Look carefully at the cons of the wire when it comes out at which direction its facing and make sure you put it back in facing the same direction or itll. It wont work right now. This whole time, weve been talking about troubleshooting. This quad and ive been kind of waving it in front of you, a solder free, build thats. True, you can put this whole quad together without ever picking up a soldering iron, not the flight controller, not the esc, not the air unit, nothing, and on top of that, you dont have to connect it to betaflight or blheli to get it going and to put This idea to the test i brought my friend ken herron out ken, has a quite a channel about dji drones uh, but he he flies fpv drones, but he doesnt know a ton about building them and i invited him to come build this drone. In fact, this is the very drone that he built uh.