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Taming Unruly Servos

FL_Engineer

Well-known member
#1
I experienced something new to me last night when replacing the glitchy 3.7g rudder servo in my yet to be maidend Mini Mustang with a 9g tower pro knockoff. I used my radio to center the new servo and all was well but after install I turned my radio off and the servo began to spin continuously (shoving itself loose from its newly glued position). It wouldn't stop spinning until I connected the radio again. Repeated the same procedure with an identical servo and get the same results. Repeated again with a different brand (3.7g) and get no movement as usual. Used the same RX channel for each servo, what am I missing here? For now I'm just being extra mindful to keep the TX on at all times (I know that's what I should be doing anyway) but it is a little unnerving to know if I forget or perhaps it drops signal mid flight it will lose rudder.
 

Merv

Well-known member
#2
I have no idea what the cause of the problem, that’s never happened to me.

This underscores why you you should always turn the Tx on before plugging in the battery on the plane. AND unplug the plane before you turn off the Tx. You never want to have a powered plane not under the control of a Tx. Having a servo go wild is a problem. Having a motor and prop go wild could be a disaster.
 
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Timmy

Well-known member
#3
I have no idea what the cause of the problem, that’s never happened to me.

This underscores why you you should always turn the Tx on before plugging in the battery on the plane. AND unplug the plane before you turn off the Tx. You never want to have a powered plan not under the control of a Tx. Having a servo go wild is a problem. Having a motor and prop go wild could be a disaster.
Agreed
 

Hai-Lee

Old and Bold RC PILOT
#4
Actually it does not demonstrate much other than the need to know your radio system and how to properly set failsafe!

As for what your plane does when the Tx is turned off, it would be exactly the same in the air when you suffer from a Loss of Signal or out of range. In the case of a loss of Tx signal and your motor/plane does not have a properly set failsafe there is increased risk of actually injuring or killing someone. On the ground at least you can change the setup to make it safer which is niot an option if the first time you find that your setup is faulty is as you watch your model cross the horizon or head full throttle towards a crown of spectators!

Learn what you radio does and program/adjust it accordingly. Reject any radio system that suffers from unstable operation or random changes in programming, (loss of bind,reversed channels, etc).

I have set my radio/s up for Smart Safe operation with the Model becoming inert/dead in the absence of Tx signal. I always power up my Rx first and I use a throttle kill switch for times when the Tx is on as a somewhat less secure measure to prevent inadvertent motor start, and have done so religiously for over 3 years now. More than 2000 flights in well over 100 different models all without a single inadvertent motor start, Mind you i have also had no LOS events or fly-away models, but that is another setup topic entirely.

Learn the radio system you use and set it up for the safest possible at all times. Do what is safest for you and YOUR radio at all times.

Better safe than sorry!

Have fun!
 

FL_Engineer

Well-known member
#5
Failsafe is set to 0 on all channels except throttle (set to -100%). I would think it was failsafe but seems odd it only does it for those particular brand servos. I do also us a kill switch setup default to on with TX power up. @Hai-Lee I know you also use a Flysky Tx and have seen your posts on failsafe. Not sure I completely understand if your setup differs from mine but I'm open to input.
 
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Hai-Lee

Old and Bold RC PILOT
#6
My setup is simply the same as Spektrum calls Smartsafe. On doing a build/repair I test the :poop: out of everything.
I am also a little anal in relation to antenna positioning , it must be perfect or perform as I expect. I fly regualrly beyond 200 metres and those that try to follow often end up landing or dissappearing unexpectedly!

As for the meandering servos I have only experienced it once and that was in a glider running off of dry cells. as the battery voltage dropped the servos seemed to be constantly recentering. I fitted a 8.4V version of the "B" receiver and used a 2 cell LiPo and the servo drift dissappeared totally. Your issue may not be the same but stable Rx volts is mandatory!

I treat the Smartsafe operation as having 3 layers of throttle control rather than the usual 2. As for the Tx power off it becomes the absolute determiner of throttle operation.

CAUTION: If you use a mix of different brands of Tx abd Rx some difficulty can be encountered in having failsafe of any version set properly and even permanently. That is why it is important to know your radio system and how it behaves and then make your own decisions as to what is the safest you can set it up and program it for. I have a list of "GOTCHAS" for one particular radio brand but this is not to promote or beat up any radio system but rather to advise people to know what their radio system does and does not do.

Have fun!