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- เผยแพร่เมื่อ 8 ก.พ. 2025
- HXT-900 servos can jitter when used with a heavier servo, maybe on the elevator. This shows the effect and a solution. It will vary with each installation due to wire length and equipment used, but the theory is the same. I use small metal gear digital servos on the elevator as it's most important and I've broken a few plastic gear servos on landing.
I never in a million years thought it would WORK!!! I assumed this was going to be another video where the problem was solved for everyone in the comments except me, I was wrong! Thank You So Much Man, keep up the great work!
Me: working on a small personal project, trying to relax and forget about the ongoing pandemic
Servos: 0:08 CORONA
I thought the same thing. Why is that word following me???!!!! LOL
Lmao
Legit
Most uncanny experience since lockdown lol
Didn't expect it to work ... had ZERO hopes but IT WORKS LIKE MAGIC! lesser and lesser jitter with every coil ...
man you are sent from above . perfect fix. didn't believe my eyes . THANKS
It really works!!! Thanks a lot, we had been working on our capstone project and we had servo jittering as well, and it was inconvenient to solder the capacitors in. Well, until we found your video. Bought some small ferrite cores, and it worked like magic!
Its great to see more Kiwis posting about RC. Such a great hobby!!
Awsome vid! Gunna sort mine out today! Cheers dude
Hi there, thank you for making those small video snippets with good informative info.
This is what I like about TH-cam, finding all those gems of info needed for a more or less a newbie in the RC hobby :)
Regards from Norway, Erik
This solved the issue I had with my servo. Thanks!
You deserve 1.million subscribers
For those that after trying this still have the same issue: you should try using a capacitor between VCC and power supply and it should fix the jitter.
that's something a bit different...
servo jitter is caused by interference on pwm (S+)
Noise on +5Vdc is a different story, you can have smooth and stable 5Vdc and still jitter,
although root cause of the problem is however mostly the same -> servo coil.
I'd give you 10 thumbs up if I could. You saved my day. Thanks!
its so crazy how it actually works, i knew about inductors already but i find it amusing
Great demo and video-- short, to the point, and practical, useful info!! Thanks!
Amazing.
Just fixed this issue being caused by a crossfire receiver antenna jittering a servo. Put a ferrite ring on it, perfect!!! I think it’s the cause of my in flight shakes
BanditFPV what is a ferrite ring? So i could find one. Thanks much
Impressive....worked perfectly for me....thanks man!
Sorry, another delayed response. I'll have to read my Gmail more often.
It is OK to mix analog and digital servos. Digitals put more strain on the power supply. Proven reliable, metal-gear analog servos are just as good as digital for most applications where you don't need the faster response that digitals can provide.
Awesome. I had the same problem once but the noise was coming from the external bec. After adding a little core with 4 turns the servo twitch stopped. The servos were just regular analog though. I've now noticed that some of the newer UBEC's already have the core installed on them.
I also check other website and so it seemed the HXT900 is very prone to jitters. I crash my aircraft using this servo twice. Although on the bench , the servo doesn't jitter but in the air, the aircraft was flying fine ,then it went out of control mysteriously ! No HXT 900 servo on any aircraft for me!
Put a large bypass capacitor across the 5V line and ground connected as close to the servo's as possible. That should prevent interference too.
Either way, ferrite increases the inductance of the wires, and the way it is done, common mode rejection is increased. (AC noise that's common to both pins, as in not differential) The effect is that the voltage will sag between the digital servo and inductor. That could be an issue it if was a lot, and take away slightly at the speed of corrections and performance. So a bypass capacitor on it would be very helpful. And also prevent electrical noise from being conducted to the rest of the servo's.
Great answer sir! And what exactly configuration of this capacitor can I use for this video setup?
I have the HXT servo, they jitters like crazy.
You are awesome thanks for this mate 👍👍👍👍👍
does the circular core has to be a magnet?
u can also twist ur servo wires and add a cap to the power wire
This is a good idea, every bit helps.
Twisting the wires reduces their ability to pick up and radiate interference if the signals or currents carried are ballanced. The power supply current is ballanced between +ve and -ve. Capacitors help a lot and are much better with a toroidal core added, or you don't need such a large capacitor.
When I was testing some small 12g metal gear digital servos I noticed current draw spiking to about 9 Amps, but for only very short pikes. Capacitors can easily suppress most of this and it doesn't bother most BEC/UBEC. These current spikes generate interference that can upset other equipment in the model such as reducing radio range.
Awesome 👍 ill give it ago cheers
Thanks for the solution, would you kindly tell me how to remove the noise of the servo motor
thx this helped very well
Great info video, thanks..
Thanks great video mate!!!!!!
may i know what is the actual reason behind this jitter? and how wrapping around the metal core addresses this issue?
+CA Hau The digital servo draws current from the power supply (the receiver and ESC or BEC) in very short but high current pulses. So the average current is low, but the peak current is high. These high current pulses upset the smooth supply voltage and cause interference that upsets the other servos. Especially servos that do not have good filtering already built in.
The circular core adds inductance to the lead and filters out some of the interference. Some interference still gets through, but if it is small enough that it does not upset servos etc. it doesn't matter.
Better filters are possible and advisable on larger, expensive or more dangerous models. But a filter core is small, cheap, simple to fit, and usually works well enough.
I always add a extra filter capacitor to the 5V power directly at the receiver for some extra safety margin.
+PMB-NZ thank you for the informative and prompt reply! Am i right to say that if i am only using a single unit of servo motor, the jitter can be solved just by either connecting a capacitor between 5v and ground or resorting to ur method?
+CA Hau I suggest both, the capacitor and the inductor core. You could try the capacitor first and add the inductor core if still a problem.
Keep the capacitor lead as short as possible.
+PMB-NZ Where did you get the capacitor and do you know the spec? Not clear on how you have the capacitor on the lead.. is it just connected to the positive and also to the negative (ground)?
+theskyisthelimit I just use 2200uF or 3300uF electrolytic capacitors rated at 6.3V, because I have a lot of them. They were originally for repairing computer mother-boards. +ve and -ve capacitor leads just connect to +5V and gnd (red and black) at the receiver. Keep the capacitor leads as short as possible.
I enjoyed this video.
I use it too in my bicopter. When the bicopter is not being armed, the servos go very well. But when that is armed, in throttle (over min throttle) the servo moves slowly to the left and the right 0 not center - whats; wrong?
Excellent video... hard to beat the HXT900 for the money LOL.
true, if they dont break on you before you get to fly lol, ive had bad luck with the little suckers lately the two 2 top gears seem to always break, also beware of the replacement gears for the HXT900 i ordered 10 sets and the 2nd gear down its tall gear is incorrect and will not mesh with the output gear, at least the sets i bought from HK , ended up having to send them all back. wish they would fix this!
That's not good for business as HK relies on being able to provide low cost batteries and servos to sell their products. I guess I should have said if you get a good one from a good batch... And I just got the popular 800mm Reaktor 3D plane that when you put a yardstick down the side of the fuselage the tail is almost one and quarter inches off to the side and it looks more like a banana than a plane's fuselage, and the wing looks like it has two different airfoils with one side visually thicker than the other side that has a sharp leading edge like on a fast flying pattern plane. To say this would be the worst flying 3D plane is an understatement and now I'm kicking myself in the head for not getting the Twisted Hobby's Crack Laser instead due to shipping costs and seeing I did not get the only banana being sold as a 3D airplane making sending back for a new one a risk. First negative issue with a HK product so hoping I get a straight one after sending it back.
My Techone Tempo measures right on and expected the same from it's little brother. I'll send it back and with the added shipping costs that's higher than most companies I didn't save a penny and ordered a lot to go with it. Could be my last plane order from HK as too much "savings" is going into shipping costs. I suspect the people making this stuff are getting angry as anyone with no experience could have done a better job. If the wing was OK I'd just unglue the hot glue and straighten the fuse but nothing can be done to fix the wing within reason. ERRR!
As for the HXT servos despite the usually good reports of dependability and fairly good performance I only use Futaba or equal quality servos. I have never had a servo fail except one and that was not the servos fault I purchased used with a dry bearing that rusted out after a year. But seems even the best amazing new servos coming out made by the new companies popping up fail once and a while and Futaba has backed down keeping up making better servos due to low profit margins showing the danger of buying "cheap". Just didn't try using a top quality digital servo that centers and holds it position under load well with no gear slop as it's hard to go back and be happy with your plane. This hobby is addicting and good servos are just one of many drugs used to keep you hooked;-)
John F Hendry Update HK seems to be matching Horizon Hobby in customer service. See what happens. Need to seed in the pictures and cell phone was no good enough and my real camera's batteries kicked the bucket and took a while to find the power cable.
Jeremy Vest
I don't think these small servos are as good as the original HXT900s from when I first bought them years ago. Just the gears don't seem as well made. I've still got quite a few operating.
I've been going off HK a bit in recent times for more technical bits. I've bought a few of their Multiwii flight controllers, most of which are modified copies of other boards. As copies they are not as good and lack basic information.
HK are still great for most other parts.
There's also another issue. If you put a digital servo on that receiver (not digital) the servo (HTX900) will go into analog mode wich is not it's best mode.
You should only use digital servo when you have a digital capable receiver or FC. In fact most modern fc's you can set the puls speed/width for a digital servo.
In every other case the digital servo will be in analog mode which causes the jitter.
I forgot to say that the advantage of digital servos (speed and torque) can still be used but you should chose all digital servos in that case, or use your solution if weight and space isn't an issue)
I have a ferrite rod from a radio kit.
Im itching to use it for something
Good demo.thanks
Great video.
thank you SO MUCH
Crazy thing is this was 9 years ago
Hi PMB....please advise if it is ok to mix digital with analogue servos in a plane....from your video it looks like it's possible without any problem.
I want to replace the analogue servos for digitals in the wings for the ailerons and leave the other analogue servos for the other control surfaces as they seem ok.
The reason is because I am not confident with the existing 645MG servos centering properly. I am using dual ailerons and elevator set up in a DX7s Tx.
I got the ring cores from Soanar/Jaycar but something similar should be available from Digikey, Mouser, Element 14 or RS Components. The bigger the core the more effective it is, but in model planes you also want to keep the weight down. Any core is better than none, and the more wire turns the better.
I'm getting a little jigger from my high-tec 645 what is it you're using that you're wrapping around the wire exactly
ThankX
Do you have a specification on the ferrite core? And a vendor recommendation? Amazon has some but they are one once, which much larger than yours.
You could try something like the HF60T18X10X10 from Digi-key. There are so many materials and specification. The ones I used came from a local New Zealand hobby electronics supplier many years ago. They still list them but no data.
Hi, just came across rthis interesting video while trying to solve a servo interference problem on a model railway. I have numerous 9G servos on the layout and some get interference (I believe) from the track power fluctuations when locos run over rail joints or points (turnouts). Would this solution help? Cheers!
They are twitching cause they are scared of corona.......LOL LMAO
I tried to do that but I just can not rotate the servomoterur in the opposite direction!! :/
Is that a metal core?
It's a ferrite core.
What is it that you put on the wire?
que es lo que husas? es un iman? o un metal normal como decir una tuerca?
I am not sure exactly. The cores are sold for this purpose, lower frequency rf suppression. RC hobby suppliers and mail-order electronics sell them.
Interesting idea. I wonder how effective a nut would be. I expect it would have some effect, but would be heavier for the same size.
My helli weighs about the same as that ferite ring
yea that is the downside of this solution. any other suggestion?
How about if I make 4 turn?
The more the better?
Yes, more is better.
thanks for that, do esc's generate more noise than servos?
Nope. (no pun intended)
@@Antonluisre lol, no pun found
Can you add More than 3 servos to the one receiver? I would need it for my latest invention :D
Would a capacitor in parallel work the same way..?
Thanks!
Not as effective.
The Green Ring , What is this ? name, please . thank you
ferrite core ring
Why does the jitter matter ? How does it negatively affect anything ? Do tell !
Try flying a model that does its own unrequested unputs on other flight surfaces.....Do you see the problem now? lol
Does anyone know why my servos twitch when i touch metal in the car with something metal?
where do you buy that part from?
Did you find out where to get these parts? I was wondering too
Another solution: buy decent servos to begin with. the blue little things only cost $5 or less but you get what you pay for.
I have had jitter issues from name brand servos too. I agree, don't risk expensive planes with cheap electronics.
What material is that O ring made of?
a high magnetic permeability material
wow that is so simple.
i did try on emax servo but still the same problem
vandamn jaunclode hey have you figured it out? I’ve got emax servos and they go nuts when I disarm my motor.
Have a problem, dont know where to go, so i'm coming to you. I got the Flysky CCT6B Tx and Rx.
1. I bound the Tx and Rx. Power to Rx is from a 9V DC battery through a IC 7806 - for 6V out.
2. After bound, the servo worked fine, (Ch1, Left and Right Control Stick). Turned 30 degree one side, back to center and turned 30 to other.
3. During my second approach, i added another servo (metal Geared), when switched on both started jittering. Dont know why.
4. So, i removed it and tried with one servo, again the same jittering at the moment power is on to Rx, and continuous the jitter.
I dont understand what to do. Any problem with the connection. Plz do help me if you can. What makes it to jitter.
read my above comment ,low current or noise is probably the cause of ur problem
Hello. Sorry, took me a while to see this.
What type of 9V battery? The small ones won't supply much current, and the voltage will droop. Servos often draw high peak currents for very short times. You need an oscilloscope to see it.
The 7806 regulator is not the best in this application. I should have the input voltage always at least 3V higher than the output voltage. 78xx regulators can easily oscillate at high frequencies if not decoupled correctly (capacitors on input and output.
A LDO (low drop-out) regulator would be better. But manu of these draw a high quiescent current (current draw with no load).
Good luck.
I have same problem, but it started happening after two weeks of normal operating, what is up with that, are my servos damaged (i highly doubt that) or is something else going on?
Or just use analog servos
Ummm.... while it solves the problem, adding ferrite core will puts a considerable weight to the overall final build.
Carona servo 🤔
good explanation/video.
good demo, thanks..