Moving to Betaflight 2.5.x - Throttle settings - min, max, min_check etc.

[Roland Sausage]

I followed a facebook post to a recent video about throttle settings.  I';ve never really considered it before and always ran motor stop with min throttle set approximately and full throttle set at 2000.

Moving to a newer version of betaflight with airmode got me thinking more about my setup.  I';ve set up a separate arming switch and a three way switch with airmode as middle position and airmode with buzzer as bottom position.  I';m not too sure about setting min throttle and min_check though.  I';m not sure how low to set my motor idle speed - I';ve got them spinning without stuttering but with prop load I might not have them high enough.  Landing is going to be a new experience too - disarm before touching down?

Does the guy in the following video speak sense?  I';ve watched the video 5 or 6 times now and I';m getting my head around what min_check does but what he suggests about leaving 20us either end goes against other advice I';ve read about setting max throttle at 2000.  Is it not necessary to leave any headroom for FC correction at full throttle any more?

Also, his advice about setting ESC min and max in BLHeli then never calibrating again - any good?  It';d be great if so.

https://www.youtube.com/watch?v=CnYr5cwYwIY&list=WL&index=3

This has also been helpful to me:

https://www.youtube.com/watch?v=WFU3VewGbbA

Any advice on this would be appreciated.

[Cheredanine]

Frankly the guy is a bit off, he doesn';t even understand the symbol for micro seconds, it is not us but μs

Let';s deal with a bit at a time

Min and max check are signals from the RX to the flight controller. As long as you are in that range the quad believes you are telling it to do things with the throttle, typically this is 1100 and 2000.  Your signal should actually go from 1000 to 2000. That gicpves you the bottom 10% of your throttle as deadband for things like stick arming.
With air mode the general advice is to switch arm rather than stick arm to avoid flipping the quad whilst arming and disarming, accordingly min check can be lower and I believe Boris has lowered it to 1050 or 1040.
This is fine you don';t need to touch it

Min command, min throttle and max throttle.
These are all signals sent to the motors by the FC.

Min command - is sent when the motors should be stopped. Generally the default value of 1000 is fine you only need to bother moving it if your motors move or twitch (other than the plug in twitch) when they should be idle (when the quad is disarmed or motor stop is active)

Min throttle and max throttle are the two extremes of signal when the motors are moving.
Min throttle should be set as follows:
In configurator, on the motor tab spin up the motors individually and see what speed they spin up at - not just stutter but actually the value they just start to spin. It may vary slightly from motor to motor, let';s say they spin up at 1029, 1031, 1034 and 1033.  You take the highest value (1034 in the example) and add 10 (1044) that is your min throttle - some people say more but that has always worked for me, if you have motors stopping when they shouldn';t then up it a bit. (A more specific example my last quad all motors spin up at 1020 so min throttle is 1030)

Max throttle - in 2.5.1 and most versions, set it to 2000

All that is pretty much verbatim advice from Borisb, the creator of cleanflight. (Not me)

You should always calibrate after changing these settings and the latest advice from the betaflight gurus is you should always calibrate ESCs from the configurator NOT on the ESCs directly, this is because it does not matter if the values are set to the same thing between the ESC and the flight controller, what matters is they think they are, if that makes sense, what the FC sees as 1234 the ESC may see as 1239.
By setting them manually this can lead to mismatch. Where';s when you calibrate from the FC it says to the ESC this value here is min throttle, the fact the FC sees it as one thing and the ESC as another doesn';t matter because they both recognise the value, regardless of what they individually think it is, as the same and they are syncd

Generally a single switch is used for arm and air mode - dissarm, arm, arm and air mode.  No reason to have buzzer on your arm/airmode switch, indeed if you want to activate lost quad the last thing you want is air mode to activate and spin the props

Nowerdays I have gone back to having motor stop enabled, it gets overridden anyway by airmode so I just flip airmode off on takeoff and landing
Another approach is to have "stop motors at any throttle" or whatever the setting is on the config panel disabled, this means the motors do not stop when disarmed until you also drop the throttle, you can then dissarm as you come in to land and the quad will still fly until you drop the throttle

[atomiclama]

Holy Molllly Cheredanine

Why don';t you just write up a proper sticky guide to setting everything up and post here.

[Roland Sausage]

Thanks for taking the time to create such a detailed reply  it';s really helped my understanding.  I';ll get flashing 2.5.1 and make some changes.  Here are my thoughts...

With air mode the general advice is to switch arm rather than stick arm to avoid flipping the quad whilst arming and disarming, accordingly min check can be lower and I believe Boris has lowered it to 1050 or 1040.
This is fine you don';t need to touch it

I saw mention of that in release notes, I';ll update to 2.5.1 and leave it at default as I had messed with it on the advice of the video I linked to.  The guy in the video suggested it should be at or below what your ESCs are calibrated to - I currently have it at 1020 matching his advice on ESC settings.

Min command - is sent when the motors should be stopped. Generally the default value of 1000 is fine you only need to bother moving it if your motors move or twitch (other than the plug in twitch) when they should be idle (when the quad is disarmed or motor stop is active)

Min throttle and max throttle are the two extremes of signal when the motors are moving.
Min throttle should be set as follows:
In configurator, on the motor tab spin up the motors individually and see what speed they spin up at - not just stutter but actually the value they just start to spin. It may vary slightly from motor to motor, let';s say they spin up at 1029, 1031, 1034 and 1033.  You take the highest value (1034 in the example) and add 10 (1044) that is your min throttle - some people say more but that has always worked for me, if you have motors stopping when they shouldn';t then up it a bit. (A more specific example my last quad all motors spin up at 1020 so min throttle is 1030)

Mine are all spinning up around 1019 so I';ll set min throttle to 1030.

By setting them manually this can lead to mismatch. Where';s when you calibrate from the FC it says to the ESC this value here is min throttle, the fact the FC sees it as one thing and the ESC as another doesn';t matter because they both recognise the value, regardless of what they individually think it is, as the same and they are syncd

This makes sense and was part of what was confusing about the suggestion in the video to set all ESCs via BLHeli Suite to the same values.  Thanks for explaining that clearly.

Generally a single switch is used for arm and air mode - dissarm, arm, arm and air mode.  No reason to have buzzer on your arm/airmode switch, indeed if you want to activate lost quad the last thing you want is air mode to activate and spin the props

I had visions of myself overshooting the middle switch position when turning airmode off to land or while in flight and disarming the quad.  That was my reason for a separate arming switch.  Would you recommend the three way switch approach?  I don';t really need a buzzer switch as I used to have it set up to activate on failsafe and I';ve got a loc8tor fitted too.

Nowerdays I have gone back to having motor stop enabled, it gets overridden anyway by airmode so I just flip airmode off on takeoff and landing
Another approach is to have "stop motors at any throttle" or whatever the setting is on the config panel disabled, this means the motors do not stop when disarmed until you also drop the throttle, you can then dissarm as you come in to land and the quad will still fly until you drop the throttle

This is very helpful info.  I had no idea airmode overrides motor stop.  I';ll just keep motor stop enabled then.  So, that would mean armed with no props spinning, take off, flick airmode on, fly, come in to land and flick airmode off, land, props stop on throttle down, disarm?  Brilliant.  No juggling the disarm switch as I';m landing - is that right?

Thanks again!

Jon

[Cheredanine]

Thanks for taking the time to create such a detailed reply  it';s really helped my understanding.  I';ll get flashing 2.5.1 and make some changes.  Here are my thoughts...

it';s no worry mate, we have all been in the possition you were in

I saw mention of that in release notes, I';ll update to 2.5.1 and leave it at default as I had messed with it on the advice of the video I linked to.  The guy in the video suggested it should be at or below what your ESCs are calibrated to - I currently have it at 1020 matching his advice on ESC settings.

the really reason fit it is stick arming and the ability to stop motors with certain settings, stick arming is a hang over from other craft, there is no real reason for it not to be 1020 as long as you calibrate the ESCs after setting it (it is used in the calibration process according to Boris)

Mine are all spinning up around 1019 so I';ll set min throttle to 1030.

should be spot on

This makes sense and was part of what was confusing about the suggestion in the video to set all ESCs via BLHeli Suite to the same values.  Thanks for explaining that clearly.

I had visions of myself overshooting the middle switch position when turning airmode off to land or while in flight and disarming the quad.  That was my reason for a separate arming switch.  Would you recommend the three way switch approach?  I don';t really need a buzzer switch as I used to have it set up to activate on failsafe and I';ve got a loc8tor fitted too.

the way I have it set up it the way I originally set it up when air mode came out, it is the way Boris recommends: three way with dissarm/arm/arm and air mode
I know a fair amount of the testers are moving to air mode always on but I prefer landing and take off with it off.

I have never flipped it too far by mistake but I suppose it depends on your radio, the taranis switches are pretty definitive, I have no worry of them going too far, also I have the amber voice pack on it and audio tracks, I did get a bit carried away I can';t mistake where I am :)

This is very helpful info.  I had no idea airmode overrides motor stop.  I';ll just keep motor stop enabled then.  So, that would mean armed with no props spinning, take off, flick airmode on, fly, come in to land and flick airmode off, land, props stop on throttle down, disarm?  Brilliant.  No juggling the disarm switch as I';m landing - is that right?

Yep that is exactly what I do.

Thanks again!

Jon

it is no problem, I spent long enough struggling with this myself in exactly your possition, all sorts of duff info out there.