Benefits [and down sides] of HIGHER PWM Frequency! 🙀💪

[@SkySeeker]

Recently tested 96kHZ with thrust linear at 25. Drone flys amazing, ultra smooth, and very responsive. I could even reduce filtering as the motors are much cooler now. Prop wash is completely gone. I was so impressed that I am switching all my quads ESCs to enable 96kHZ.

[@AerialWaviator]

Great insights. This perspective is just from the ESC, but to properly understand what happening we should be looking at ESC and motor together. A motor coil is an inductor and has a resistance, so unlike the MOSFET being driven by a digital signal, the coil will alter the power waveform. (a ramp at constant rate of change vs instantaneous vertical change in power) Depending on kV of motor, it's inductance (L) and resistance (R) will vary and have a power ramping time. This is governed by τ = 1/(R*L). It takes ~1τ to ramp 63% of power and ~5τ to ramp to 99% of power level driving the inductor coil (ie: motor windings). The point I'm working towards is that at lower PWM frequencies; less than 5τ (the natural frequency a motor coil), the coil will not become fully energized prior to the MOSFET turning off. Thus actual power would be less than expected if just considering theoretical square wave power source. At higher PWM frequencies there will be less variation a motor coil energing (de-energies) so coils will provided a more consistent power level with what is expected. The effect of motor coil on power soured by the MOSFET could be viewed by examining one of 3 phases powering a motor on an oscilloscope. (my insight into ESC firmware is limited, so not sure if ESC make compensations for this effect; but to do so they would need parameters on motor kV, (ie: R, L values) unless making generic assumptions) This deeper detail than the video; looking at the square MOSFET driver waveform and duty cycle. Thought it worth mentioning, for possible future topic (or those wanting more detail).

[@PIDtoolbox]

I've been flip-flopping between 24khz and 48khz. I've tried TL to help give better low throttle torque, but I still find 24khz to be better in this regard. For super stable cruising even in windy environments, 24khz just seems best. Now for propwash, I don't know why but 48khz almost always seems better. This is all anecdotal of course :) Awesome data here though! It will be fascinating to begin to understand how these ESC settings contribute to various flight related issues

[@chrissofpv3017]

Really interesting,many thanks.I,m off to Spain soon..so I can experiment more easily with the own frequencies...(e.g.its not raining,or blowing a gale,DAILY,..like here in England!)

[@DominicClifton]

Woohoo, I did the same 3 years ago!

[@tehllama42]

Finally catching up - I'm amazing at how dead time dependent that is, even at the low end for braking torque, that's crazy. 7" Is plenty happy on 48kHz, but yes, adding thrust_linear into the equations drastically helps with control at idle.

[@MCsCreations]

Really interesting, Mark! Thanks a lot! 😃 Stay safe there with your family! 🖖😊

[@banzaiib]

Built my first drone in 10 years last week (yeah i'm old)... used stock betaflight settings and stock timing (24kHz) on a 7" 1300kv, mamba F722 build. Motors so hot i couldn't touch them after 5 min flight. 1350 mAh of the 6S battery used. Just tried setting the max and min pwm to (as an experiment) 128k in blheli_32. The motors barely get warm now, and i'm getting 30% greater flight time. Flew for 6 min and only 900 mAh used. I thought my telemetry was borked, but the charger confirmed it! Big yaw inputs cause a throttle blip for some odd reason... but I think i'm headed in the right direction. Will probably set a lower min PWM freq, but will try to compensate with PIDs before that.

[@DronoTron]

This is amazing. This shows why 48khz is recommended for small whoops motors since they have less inertia so the initial and braking torque doesn't present a great issue. But the added thrust allows for more efficient energy usage, which is critical with the tiny lipos they use. Very interesting info , thanx!

[@princesfpvdrones]

You the man as usual, I just put my LR Flywoo 4" together and now going to set it up for tuning using your info here, that makes sooo much sense!

[@Gosuminer]

Until now I had 24 kHz on all my 5" quads and 48 kHz on 3" and smaller but I will set my 5" to 48 kHz and give it a try. Of course, rapid breaking is desirable but I doubt I will notice and smoother motors are always nice.

[@PIDtoolbox]

super interesting!

[@CgitEinsteins]

must try this

[@ZombieSS77]

Fun FYI, when dead time > 5% of the PWM period (50kHz = 20us period, so dead time should be < 1us) it increases low frequency harmonics which will reduce delivered power by a few percent and can also increase motor heating.

[@Samiron]

I'm wondering how to convert two digits in blheli_s firmware deadtime (30 for example) to µs.

[@Dennis-ve2vd]

I just love this channel! High quality content.

[@brknpropfpv3899]

Thnx for the cool data. Do you mess with motor timing? Should I? 😎🎮🤙🏻stay up

[@eskrace1104]

Been going back and forth with 24 and 48. It depended all on the build, but for bigger than 6" builds I've had most of the success with the tuning on 24khz, but then again with a lower timing than 23 degrees.

[@BBFPV]

Saw you yesterday at Pawel stream

[@vonpwnz0r]

Regarding whoops, it is my understanding that the 1S whoops doesn't have a FET-driver and that the MOSFETS are run directly from the BB2 MCU. That gives the 1S boards an incredible deadtime of just 5. If you look at the almost similar 1-2S boards, they need a FET-driver and have more normal deadtimes of around 50. This makes the 1S boards (like Mobula6) prime candidates for 96 and 48khz.

[@alkamotors158]

Take an esc and look at the output pulse length to the motor at 24khz and 48khz on the scope. Its not proportional at the same dshot value. You would expect the pulse at 48khz to be half of 24 but it won't be.. It will be slightly higher.

[@airdronelongford2027]

Thanks for that 👍

[@SKIDOOSH]

Always great info..TY sir!

[@Shauny_D]

I get desyncs in 48khz but no issues on 24. (With whoops blhelis) or I think desyncs... Heavy or sudden throttle changes and it flips or motors cut out. Or if I cut throttle after a high throttle maneuver the motors spin up instead of slow and the quad climbs instead of decends.

[@Krunked]

48khz, 23 timing, demag high, thrust_linear = 25. :)

[@uavtech]

Oh I know it. But see others comments as well.

[@HaraldLabout]

I run all my quads on auto timing recommended by Bardwell for extra smooth response. Picked up that tip 2 years ago and since then all on auto. Bad tip? 23 better?

[@Krunked]

@@HaraldLabout yes 23 is better..

[@mattimehner9193]

I also found this to work best, but additionally I had to increase the PIDs overall by about 20% on my 5 inch quads. On one quad I got some issues with D oscillations which are controlled really nicely with tpa of 0.8 at a break point of 1250. Posted an extended post on that over on FB just a few minutes ago, link to the blackbox log is there. facebook.com/groups/291745494678694/permalink/945354222651148/ Still you can feel the loss of authority when hovering in front of an obstacle. So I am staying on 24khz with my freestyle builds. 48khz is the way to go for racing rigs (for me).

[@j.finesseflights1403]

Good to kno, thanks bro!

[@Inertia888]

The 'UAV Tech BF Preset for 5-inch Quads, With Go-Pro' (up to about 700 grams AUW) has two options for PWM: 16 & 24kHz or 48+kHz > If in BL Heli-32, I have it set for 24kHz (Low) and By RPM (High) on an ESC with 128kHz capability, ?> Which option should I select? 16&24kHz or 48+kHz --- Both ?

[@MrSmithersFPV]

incredible as usual!!!

[@ivanrossi7257]

summary what is the best frequency?

[@sjoervanderploeg4340]

I've stuck to 24kHz on my bigger quads, but 48kHz on my smaller ones. As the frequency goes up, resolution also goes down and this is very noticeable on my bigger quad that just feels lackluster at anything above 48kHz. With lackluster I mean it smoothes out the throttle band too much and feels much more floaty.

[@torchbeareraerial4660]

I have a quad that feels like it drops too fast. Would increasing pwm maybe help with that?

[@sjoervanderploeg4340]

@@torchbeareraerial4660 no.

[@-xeL]

since i got an esc that is shipped with 96khz enabled by default i was wondering about the pro's an con's - thanks for that!

[@CrashAndRebuild]

Seems like we need a firmware capable of adjusting PWM frequency on the fly based on erpm of the motor so we get the best of both worlds. Low end torque at slow speed with lower pwm timing and more top-end thrust and smoothness in the upper rpm bands with higher pwm timing.

[@uavtech]

Auto-PWM exists. Just not in stock BLHeli_S or 32 (yet).

[@jjj25313]

Very cool! Im also curious as to how it wears out the esc differently?

[@themountain59]

There is a big discussion going on between RC crawler enthusiasts in the moment....What kind of esc would be suitable to have a , lets say 1800Kv motor, run smooth and ....very important silent ? 48kHz....more....?? Awesome video BTW ...kudos !

[@uavtech]

Higher PWM makes for smoother, but less breaking torque.

[@themountain59]

@@uavtech Yes I know ...holmes hobbies introduced a esc recently but its limited to 4s and the BEC is not what they thought it was. What would you consider a good ESC for low rpm running ? I read something about neutronrc coming out with a Gmodel esc that has AM32 firmware.

[@trajanfpv]

Interesting stuff!

[@FreshPanda97]

24khz-128khz vs fixed for freestlye ? dont get it :( so confusingfor me

[@martinchristiansson658]

First of all, great content! I have a question, since I have developed my own flight control hardware and software, I am now getting interesting in ESC and how they work. Perhaps you can answer this? : how can a ESC know when to apply active breaking? For me its strange since FC only sends "power commands" input to ESC and the rpm will be accordingly all factors considered. BR Martin

[@TechnicallyTom]

I usually use 48 with thrust linear but I do not run at the recommended setting of 25. After testing and finding that it did work, I got curious whether that high a setting was necessary. I experimented a bit and fount 10 to 12 was enough to clear up the issues I was getting with 48khz PWM

[@highducky420]

is it normal that you can hear the difference between 24 and 48 khz when you arm the quad? when its set to 48KHZ you can hear that they run smoother

[@uavtech]

Yup

[@ibnfpv]

so with 48khz, it is more nassasery to set the timing to 23-25 to overcome the less magnet timing and compensate it in this way?

[@benfoust1]

so i know 24khz might help my propwash performance but would setting the thrust linear on 48khz give the same effect?

[@controlflow89]

I wonder if it's possible to make PWM frequency dynamic in ESC firmware... 48kHz at high throttle values for more thrust, 24hHz at low throttle for better breaking and more low end torque (less probability of de-sync on throttle chops/on reversed flow through props)

[@uavtech]

There is Auto PWM in the testing from 24 to 48khz. It seems like it takes too long to update, which makes less thrust. But check it out.

[@Krunked]

I wonder if kiss/fettec ESC's do this.. seeing they are 128khz. Seems like a dynamic pwm adjusting with throttle makes. Sense.

[@uavtech]

I know APD ESCs do it. But that just means I know they have an Auto option. I have no idea what it does or if it is even better. Like Timing, Auto might not be better.

[@kumquad_fpv]

@@Krunked the last firmware for the fettec ESCs has some kind of dynamic pwm. But you also have to take in mind that the fettec/kiss ESCs are simulating a sinus curve and not a fixed rectangular one. blog.seidel-philipp.de/kiss-sinhybrid-sinwave-backemf-hybrid-kommutierung/

[@Krunked]

@@kumquad_fpv yeah. For sure.

[@pablofpv]

Great video, could this be the reason for the throbble issue I had that went away When I switched from 48KHz to 24KHz PWM? As that would make sense, as the issue only occurs When you chop the throttle to a very low idle and the motor breaking torque would Be lower at 48KHz?

[@uavtech]

Yep

[@jtaraskus]

These video kiks me deep in hardware :) Thanks!!!

[@ericklassen13]

Any thoughts or testing on variable PWM?

[@uavtech]

Not that I know of.

[@ZylonFPV]

This is very interesting - I’ve been having a lot of low throttle oscillations using a blheli32 40a hobby wing 20x20 esc. Do you think dropping down from 48khz to 24 would fix that?

[@uavtech]

Yes, or adding Thrust Linear should help too. 25.

[@towersfpv9575]

Yes it worked for me on my 7in.

[@rollinondubz2002]

Would 48kh cause my 2.5inch drones not wanting to turtle as well.. i seemed to noticed it after doing 48kh

[@uavtech]

I reckon it could. Switch back and test. However, on a 2.5", it does help with battery time, soooo...

[@ariafpv]

Would a variable frequency that is changing automatically in flight make any sense? Or wouldnt that work?

[@uavtech]

Auto PWM tested didn't seem to perform as well for some reason. Take a look.

[@Redbeard682e]

Anyone have input on what would be a good frequency to look for in a pwm for a trolling motor?

[@uavtech]

Like for a boat?

[@Redbeard682e]

@@uavtech yes more specifically for a kayak.

[@marlin-fpv]

How many notches at what Q you sat up without RPM?

[@uavtech]

3 and 300

[@afifathnin]

Would it work better with blheli32 48khz low and 96khz high

[@uavtech]

Unknown.

[@km_photo]

Using only JazzMaverick 48kHz on every esc I got, and it's mostly 16.80. What was the other firmware?haven't heard of them ever before.

[@uavtech]

Which? JESC? Alkin? Just other options. JESC seems to produce the most thrust. Check it out.

[@km_photo]

UAV Tech you have to live under a rock, not knowing about JESC but I was wondering about this other one: ALKIN? Where to find and how good is it?

[@uavtech]

It is being developed in BF Slack. I would need to search for Github. Seems to produce less thrust at the moment, but look at the comps for yourself.

[@alkamotors158]

Thrust is the same for the same output power.. please contact me for details.. look at 10:34 in the video . you can find the project here. github.com/conuthead/AM32-MultiRotor-ESC-firmware.

[@IvanEfimovLimon]

Does this explain somehow why whoops fly longer on 48khz?

[@uavtech]

Less breaking torque. So motors are not cycling up and down on micro RPM changes as much. Seems for the small motors, less mass, it has an impact.

[@nistax2880]

0:49 literally wrong, like not true at all. escs use "on/off" and not "in between" because it requires a lot more components to achieve that "in between". and it doesn't have that much difference on the motor. But it is possible to have an ESC that does output smooth voltage radher than pwm , it's just much more complicated

[@uavtech]

Right, i was just saying how ESCs work as of today. I'm aware of VFDs.

[@nistax2880]

@@uavtech well you said "electricity" not "ESC", odherwise great vid man

[@gotdrift8]

Bro how do you even know this stuff? My guess is you do something to do with this tech for a job?

[@DronePlayground]

👍👀🇭🇷