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Motor Pulsing

Old 05-24-2017, 05:35 PM
  #1  
garyp1029
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Default Motor Pulsing

I have a new (7 or 8 flights) EFlite T28 (older version with fixed landing gear) with stock prop (balanced), motor, and 30A ESC. The motor makes a pulsing noise in flight which has occurred using several different battries, all of which were fully charged. What is the cause of this?? What is the remedy?? Thanks. Gary

Last edited by garyp1029; 05-24-2017 at 07:47 PM.
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Old 05-24-2017, 09:22 PM
  #2  
Turbojoe
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Sounds like LVC. Low Voltage Cutoff. Your batteries may be charged but not up to the demands of this motor so voltage will sag below the preset cutoff voltage programmed in the ESC. A static full throttle run up using a wattmeter will confirm this. A DVOM will work too if you can probe into the battery leads safely while it is run up.

Joe

Last edited by Turbojoe; 05-24-2017 at 09:23 PM. Reason: spelllling
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Old 05-24-2017, 11:22 PM
  #3  
ron_van_sommeren
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How high was the current you measured at WOT? Some for rpm.
What are the battery specs?
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Old 05-25-2017, 12:20 AM
  #4  
garyp1029
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Will put the plane on wattmeter tomorrow morning (right now it is well over 100 in our Tucson garage where my planes are stored--NOT the batteries). Batteries are all Turnigy 11.1 v, 25-35c, 2200 mah. Have used same batteries within the last 5 days in a Formosa and Leader 480 without any problems. They were fully charged (4.20/cell) before todays flights; read 3.8-3.9 per cell after each 5 minute flight. Gary
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Old 05-25-2017, 01:17 AM
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Turbojoe
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If the batteries test good then check ESC programming. Per the website: Programmable low voltage cut-off with settings for 3S Li-Po (9.2V), 4S Li-Po (12V) or 74% of battery starting voltage. 9.2 volts is pretty low and your packs would have to be complete junk to sag below that in normal flight. I'd expect them to come down very hot and puffed. I'll bet the ESC is set for 4S operation.

Link to the ESC manual is HERE. Click on manuals and support.

Joe
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Old 05-25-2017, 01:35 AM
  #6  
garyp1029
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I will check the cutoff tomorrow. IF the esc is set on 4s, should I change it to 3s OR 74% (which is the default setting)? I have had these same batteries for some time and used them in several different planes without incident; they take a full charge and come down evenly to 3.8/3.9 every time, so I suspect the problem in with the esc. Gary
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Old 05-25-2017, 01:41 AM
  #7  
Turbojoe
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Yes. Set it for 3S.

Joe
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Old 05-25-2017, 04:25 AM
  #8  
dereckbc
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Originally Posted by garyp1029 View Post
I will check the cutoff tomorrow. IF the esc is set on 4s, should I change it to 3s OR 74% (which is the default setting)? I have had these same batteries for some time and used them in several different planes without incident; they take a full charge and come down evenly to 3.8/3.9 every time, so I suspect the problem in with the esc. Gary
You said you have 11.1 volt 2200 mah batteries right? That is 3S. A fully charged 3S battery is 12.6 volts and below the cutoff voltage of 4S. A 4S battery is 14.8 volts and LVC is 13.2 to 14 volts. So a fully charged 3S (12.6 volts) is completely dead at 4S voltage profile. and would certainly fool your ESC if programmed for 4S profile. .

In my eyes is an engineering oversight on the ESC manufacture. If the ESC were set to 4S, and you mistakenly used a 3S battery, the ESC SHOULD NOT ARM THE THROTTLE and go into an Alarm Condition warning the user something is seriously wrong, and not allow you to take off.

But what do I know? I am just an engineer.

Last edited by dereckbc; 05-25-2017 at 07:09 PM.
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Old 05-25-2017, 05:07 AM
  #9  
garyp1029
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Problem solved. Thanks to Turbojoe and Dereckbc. The ESC was setup for 4s cutoff. It is a new ESC which came installed in the T28, so I have no idea how or when it happened. Since EFlite has no ESC program card, I will follow the manual intructions on how to change it to 3s by moving the throttle back and forth and counting beeps. Thanks for all the ideas and suggestions. Gary
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Old 05-25-2017, 05:23 PM
  #10  
Rockin Robbins
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Problem solving at its best! Wattflyer just justified its existence. Joe and Dereck get attaboys and another day's worth of food!
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Old 05-25-2017, 06:26 PM
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Just to add a final little bit .... (I know its not OP's cause).

Pulsing of motors ... serious where it cannot fly is usually down to faulty connection of one motor wire to ESC ... sometimes causes CHUGGING ... but in lesser cases PULSING.

AS OP has now found his ESC was basically pulsing because of low voltage. My Mig29 does this when the flight battery gets low and its time to land. It's an option on some ESC's to do it instead of cut-off etc.

As RR says ... Wattflyer gets it right ...

Nigel
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Old 05-27-2017, 01:20 AM
  #12  
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Was my second plane. You will love it. When you get bored stuff a 15 motor in it and go 4S.
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Old 05-27-2017, 01:51 AM
  #13  
dereckbc
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Originally Posted by Rockin Robbins View Post
Problem solving at its best! Wattflyer just justified its existence. Joe and Dereck get attaboys and another day's worth of food!
Not a great pilot or builder as most of you know from my own questions here. But after 40 years of being an EE and ham radio working with batteries, radios, motors, controls, and circuit design I got the electrical part down and help where I can.

To the credit of the Forum I am a better builder, err repairer now than I was few years ago. To bad I cannot learn to be a better pilot. Real planes are easier to fly in some aspects, just not as forgiving to mistakes.
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Old 05-27-2017, 04:28 AM
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Judging by the ee statement i am guessing that like me you are at the age where the learning curve is a little softer, and the hand/eye team isn't as fluid as it used to be. It's all good by me. The challenge is what keeps me engaged, and pulling off simple maneuvers gets me excited.
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Old 05-27-2017, 06:35 AM
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solentlife
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Originally Posted by Vic Z View Post
Judging by the ee statement i am guessing that like me you are at the age where the learning curve is a little softer, and the hand/eye team isn't as fluid as it used to be. It's all good by me. The challenge is what keeps me engaged, and pulling off simple maneuvers gets me excited.
Getting older has meant my depth perception is bad. Landing is the good example. For some reason - my Hummer / Mig29 and similar that are basically dump on the ground jobs - I can land close to me. But serious models that require proper glide slope in and rolled landing - I have trouble getting right on the runway ... they always end up further away from me than intended. Where they should roll past me about 20ft in front - they end up 50ft or so !

Its getting that if I go home without any damage or repair to make - its been a magic day !

My latest model - the Tiger Moth has shown me that I can still fly OK - but need to slow it down. I think as my high performance stuff 'suffers' from my old hands - I will move more towards more docile stuff ! Or build a Wot4 !!

Nigel
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Old 05-27-2017, 02:14 PM
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Mr. Luther

Welcome to the not so Golden, GOLDEN Years!

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Old 05-28-2017, 04:29 AM
  #17  
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Originally Posted by solentlife View Post
I think as my high performance stuff 'suffers' from my old hands - I will move more towards more docile stuff ! Or build a Wot4 !!

Nigel

I have always liked my gliders but am enjoying them a lot more lately because they are more docile. I always take one flying and spend more time flying them than planes lately. I am off my blood pressure tablets now and really don't want to have to start taking them again.
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Old 05-28-2017, 06:05 AM
  #18  
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Originally Posted by Panther View Post
I have always liked my gliders but am enjoying them a lot more lately because they are more docile. I always take one flying and spend more time flying them than planes lately. I am off my blood pressure tablets now and really don't want to have to start taking them again.
That's awesome to hear.
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Old 05-28-2017, 08:34 AM
  #19  
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Thanks Vic Z
It was great hearing the Doc say that.
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Old 05-28-2017, 02:58 PM
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Vic Z
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Changes in lifestyle?
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