Motor power reducing

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Cheezey
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Joined: Tue Apr 08, 2014 11:38 pm

Motor power reducing

Post by Cheezey »

I'm working on my first Quad. At first, it would get about 7 feet off the ground and then crash due to stabilization and mechanical issues. The altitude that it could reach gradually lowered on sucessive tests while I fixed the problems. Today, I replaced a motor and ESC that were damaged. On my first test, it got about a foot off the ground before crashing as it was untuned. A few more tests made it lower even more. Now it won't even leave the ground. Sometimes it fails to connect to my TX. Battery is charged and balanced, meter reads 12.40V, alarm is green. All the connections are good, ESCs are calibrated.

Any ideas on what could be causing this problem?

waltr
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Re: Motor power reducing

Post by waltr »

Bad solder joints?
Quad too heavy for ESC/motor/prop combination?
Are the ESCs or motors getting hot? Are any of the solder joints or connections getting warm?
Does the battery have a high enough discharge rating for the motor/prop combination? What is the battery Voltage under load?
Does your alarm monitor each call in the battery or just the total battery pack Voltage? Could be a weak cell.

As for stability then crashing this is just due to still needing to learn how to fly plus some possible tuning of the PIDs.
These are best tuned on a string which is also good for troubleshooting problems. Tuning on a string is done like this:
http://www.youtube.com/watch?v=YNzqTGEl2xQ

Cheezey
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Re: Motor power reducing

Post by Cheezey »

waltr wrote:Bad solder joints?

Nope. It uses bullet connectors.

waltr wrote:Quad too heavy for ESC/motor/prop combination?

Shouldn't be; I haven't added more than a few grams of weight since my initial tests.

waltr wrote:Are the ESCs or motors getting hot? Are any of the solder joints or connections getting warm?

No.

waltr wrote:Does the battery have a high enough discharge rating for the motor/prop combination?

Yes. Normal discharge rating is 35C, which is 77A. The motors draw a maximum of 13A each.

waltr wrote:What is the battery Voltage under load?

I don't know. How do I test this? I get a little nervous when close to spinning propellers.

waltr wrote:Does your alarm monitor each call in the battery or just the total battery pack Voltage? Could be a weak cell.

Individual Cells.

waltr wrote:As for stability then crashing this is just due to still needing to learn how to fly plus some possible tuning of the PIDs.
These are best tuned on a string which is also good for troubleshooting problems. Tuning on a string is done like this:
http://www.youtube.com/watch?v=YNzqTGEl2xQ


OK, thanks. I worked out those problems. Still needs some tuning but it needs to get in the air first.

waltr
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Re: Motor power reducing

Post by waltr »

Nope. It uses bullet connectors.

But the wires are soldered to the bullet connectors.
Also, the battery connector and PDB have the wires soldered on.
So still could be soldering.
There have been several reports on bad soldering on the battery connector as purchased that was fine for a while then got funny, then failed completely.

I use that alarm and it does monitor each cell. Are all the LEDs green?

waltr wrote:What is the battery Voltage under load?


I don't know. How do I test this? I get a little nervous when close to spinning propellers.

Tie down the quad or setup for tuning on a string. Then connect your DVM to the battery balance connector and run up the motors.
Does the Voltage drop as the motors slow down?
If not then the battery is good. Now connected the DVM to a point past the power distribution. Does the Voltage as the motors slow down?
Is yes then there is a bad connection between this point and the battery. Now divide the circuit by moving the DVM until you find the bad connection.
If not then its a different problem.

This is difficult to troubleshoot and hard to do on a forum.
Just trying to go through items that might cause the problem and things to check.

Cheezey
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Re: Motor power reducing

Post by Cheezey »

Everything seems good. At full throttle, the voltage dropped by less than 0.1V. Anything else I could try?

Cheezey
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Re: Motor power reducing

Post by Cheezey »

Anyone?

waltr
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Re: Motor power reducing

Post by waltr »

Cheezey wrote:Everything seems good. At full throttle, the voltage dropped by less than 0.1V. Anything else I could try?

Where was this measured? At the ESC?

Did you setup the quad on a string for testing and tuning?

Another thing to try is run the Erase EEPROM arduino sketch then re-load multiwii.
Last edited by waltr on Tue Apr 29, 2014 1:32 am, edited 1 time in total.

PatrikE
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Re: Motor power reducing

Post by PatrikE »

Have you Calibrated the ESC's?

Is the Propellers mounted correct way?
I managed to do it wrong last week!
Should think one should know how to mount them after 25 years flying;)...

Cheezey
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Re: Motor power reducing

Post by Cheezey »

waltr wrote:Where was this measured? At the ESC?

At the power distribution board, where the ESC is connected. I loosened the bullet connectors and attached alligator clips.

waltr wrote:Did you setup the quad on a string for testing and tuning?

I removed the props, actually.

waltr wrote:Another thing to try is run the Erase EEPROM arduino sketch then re-load multiwii.

Ok, thanks. I'll try that.

Cheezey
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Re: Motor power reducing

Post by Cheezey »

waltr wrote:Another thing to try is run the Erase EEPROM arduino sketch then re-load multiwii.


Still didn't work. Anything else?

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Gartenflieger
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Re: Motor power reducing

Post by Gartenflieger »

Cheezey wrote:I'm working on my first Quad. At first, it would get about 7 feet off the ground and then crash due to stabilization and mechanical issues. The altitude that it could reach gradually lowered on sucessive tests while I fixed the problems. Today, I replaced a motor and ESC that were damaged. On my first test, it got about a foot off the ground before crashing as it was untuned. A few more tests made it lower even more. Now it won't even leave the ground. Sometimes it fails to connect to my TX. Battery is charged and balanced, meter reads 12.40V, alarm is green. All the connections are good, ESCs are calibrated.

Any ideas on what could be causing this problem?


Actually, there is no reason why the 'untuned' craft would crash in the first place. What happened when it crashed?

Cheezey
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Re: Motor power reducing

Post by Cheezey »

Gartenflieger wrote:Actually, there is no reason why the 'untuned' craft would crash in the first place. What happened when it crashed?


It just sort of rose off the ground, wobbling, then careened off in one direction and hit the ground. Maybe it was because I had stable mode on but hadn't calibrated the accelerometer and gyro.

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Gartenflieger
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Re: Motor power reducing

Post by Gartenflieger »

So in the meantime you had some stable hovers, but the apparent power has reduced with each flight?

In multiwii, unexpected power loss is sometimes caused by heavy vibration. If you feel safe doing so, you can hold the craft in your hand (or both hands withh a buddy at the Tx) while powering up to get a feeling for the amount of vibration and for the available lift.
Sometimes the firm grip dampenes the vibrations enough to result in more lift than would be available in free flight and you have identified the reason for the loss of power.

Another reason could be one motor providing reduced lift. Check each ESC/motor using a servo tester.

Cheezey
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Re: Motor power reducing

Post by Cheezey »

Gartenflieger wrote:So in the meantime you had some stable hovers, but the apparent power has reduced with each flight?

Exactly. It was unstable at first, but the last few times I tried it it was very stable after I tweaked the PID.

Gartenflieger wrote:In multiwii, unexpected power loss is sometimes caused by heavy vibration. If you feel safe doing so, you can hold the craft in your hand (or both hands withh a buddy at the Tx) while powering up to get a feeling for the amount of vibration and for the available lift.
Sometimes the firm grip dampenes the vibrations enough to result in more lift than would be available in free flight and you have identified the reason for the loss of power.

OK, I'll try this.

Gartenflieger wrote:Another reason could be one motor providing reduced lift. Check each ESC/motor using a servo tester.

I don't have a servo tester. Could I try this guide?

waltr
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Re: Motor power reducing

Post by waltr »

That is an interesting read but not what Gartenflieger was suggesting. A servo tested produces a PPM signal for controlling Servos which is the same signal the FC sends to the ESCs. If you do not have a Servo tester then use the Throttle channel on your RC receiver and the TX's throttle stick.

Cheezey
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Re: Motor power reducing

Post by Cheezey »

waltr wrote:That is an interesting read but not what Gartenflieger was suggesting. A servo tested produces a PPM signal for controlling Servos which is the same signal the FC sends to the ESCs. If you do not have a Servo tester then use the Throttle channel on your RC receiver and the TX's throttle stick.


Ok.

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Gartenflieger
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Re: Motor power reducing

Post by Gartenflieger »

Actually, I think you can use the vibration monitoring function within MutiWii, it must be enabled somewhere in the config.h and you have to reload the firmware without it again later, but probably easier than rewiring everything.

Cheezey
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Re: Motor power reducing

Post by Cheezey »

waltr wrote:If you do not have a Servo tester then use the Throttle channel on your RC receiver and the TX's throttle stick.


OK, I did that. One of the motors seems to 'buzz' and make noise at a lower pitch than the other motors. Should I replace it?

waltr
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Re: Motor power reducing

Post by waltr »

Try replacing the ESC then the motor.
Or swap the motor to a different ESC to see which one is bad.

Cheezey
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Re: Motor power reducing

Post by Cheezey »

waltr wrote:Try replacing the ESC then the motor.
Or swap the motor to a different ESC to see which one is bad.


OK, I did that and it had the same results. I'll buy a new motor.

waltr
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Re: Motor power reducing

Post by waltr »

Ok. If one motor's power drops off then MW decreases the power to the other motors to hold level. A bad motor explains why your copter just descends.
Lets us know if the new motor gets your copter flying properly.

Cheezey
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Re: Motor power reducing

Post by Cheezey »

waltr wrote:Ok. If one motor's power drops off then MW decreases the power to the other motors to hold level. A bad motor explains why your copter just descends.
Lets us know if the new motor gets your copter flying properly.


Nope. Replaced it, still nothing. I also replaced some screws that had fallen off, which reduced vibration a little, but still it won't lift off.

EDIT: I tried installing a fresh copy of MultiWii, but it wouldn't arm, so I went back to my old copy, and it still won't arm. I tried both the aux switch and the stick combo, no luck.

EDIT 2: I calibrated the ACC and MAG and now it arms, but the old problem is still there.

Cheezey
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Re: Motor power reducing

Post by Cheezey »

I'll provide some more information to see if it helps.

If I adjust the yaw while the motors are spinning, it lifts, but not enough to fly. Also I can get it to flip over with pitch/roll.

Is there a way to enable PassThrough mode? That might help determine if it's a stabilization problem, but I don't see it in the GUI.

ttsalo
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Re: Motor power reducing

Post by ttsalo »

If you haven't already, you could plug the ESCs one at a time directly into the RC receiver's throttle output (with the copter tied down) and test the motors one by one with a fully manual throttle signal. That should at least help verify whether you have a bum ESC or motor, or whether the problem is on the flight controller side.

bluecnc
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Re: Motor power reducing

Post by bluecnc »

I don't know if this will help, but...

For the past month I have been wrestling with a problem of instability. Or for that matter crashing. I would be able to hover for a couple of minutes and then bam... into the dirt.

I went through most of the electronics replacing them one at a time until I narrowed it down to my ESC's. They were overheating in the 90 plus degree days we have been having.

As an experiment I removed the plastic cover(not recommended) and the heat sink(kind of fell off) off of each ESC. Now the craft is steady as it was in the cooler weather.

Not saying this is what your problem is. My quad was rock solid until the hotter weather arrived.

Hope you get it sorted.

Rob

Cheezey
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Re: Motor power reducing

Post by Cheezey »

Hi! I'm not dead. Just a lot of stuff has been going on, life, vacation, etc.

ttsalo wrote:If you haven't already, you could plug the ESCs one at a time directly into the RC receiver's throttle output (with the copter tied down) and test the motors one by one with a fully manual throttle signal. That should at least help verify whether you have a bum ESC or motor, or whether the problem is on the flight controller side.


OK, I tied it down and each motor has an obscene amount of thrust. It seems like it's on the FC side.

bluecnc wrote:I don't know if this will help, but...

For the past month I have been wrestling with a problem of instability. Or for that matter crashing. I would be able to hover for a couple of minutes and then bam... into the dirt.

I went through most of the electronics replacing them one at a time until I narrowed it down to my ESC's. They were overheating in the 90 plus degree days we have been having.

As an experiment I removed the plastic cover(not recommended) and the heat sink(kind of fell off) off of each ESC. Now the craft is steady as it was in the cooler weather.

Not saying this is what your problem is. My quad was rock solid until the hotter weather arrived.

Hope you get it sorted.

Rob


Doesn't seem to be the problem, as it's not even taking off. Thanks though.

scrat
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Re: Motor power reducing

Post by scrat »

How heavy is your quad? What motors do you have and props? Did you calibrate all esc's at once with ESC_CALIB_CANNOT_FLY?

Cheezey
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Re: Motor power reducing

Post by Cheezey »

scrat wrote:How heavy is your quad?

I'm not sure, because I don't have a scale. I don't think it's too heavy, though. It used to fly decently. Also, when I tied it down, I tied it to a box filled with a set of screwdrivers and 469g of LiPos, but just one motor easily flipped it over.

scrat wrote: What motors do you have and props?


Motors: http://www.hobbyking.com/hobbyking/stor ... duct=23911
Props: http://www.hobbyking.com/hobbyking/stor ... duct=45269 (they were cheap and in stock at the US warehouse)

scrat wrote: Did you calibrate all esc's at once with ESC_CALIB_CANNOT_FLY?


Yep.

Cheezey
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Re: Motor power reducing

Post by Cheezey »

I discovered a useful piece of information!

Two of the motors aren't getting much power most of the time: when I put it on full throttle, the motors start up at about the right speed but it quickly drops off. When I use the yaw, pitch, or roll levers, it briefly gets more thrust. This was tested without a lipo plugged in, but it's consistent with what I've observed in the tests with the motors on.

Here's a screenshot:
Screenshot
Screenshot

Those behavior stayed about the same no matter how I tilted it.

waltr
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Re: Motor power reducing

Post by waltr »

Look at the YAW value from the receiver.......it is telling the FC to YAW the quad so this is the correct motor response to a command to Yaw.
Second, if the copter is NOT in the air then the FC can not get correct made since the props are not doing anything. So the motor values are completely normal.
Also, none of your stick values are properly centered. They all need to be EXACTLY at 1500 else you will see odds issues.

Cheezey
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Re: Motor power reducing

Post by Cheezey »

waltr wrote:Look at the YAW value from the receiver.......it is telling the FC to YAW the quad so this is the correct motor response to a command to Yaw.
Second, if the copter is NOT in the air then the FC can not get correct made since the props are not doing anything. So the motor values are completely normal.
Also, none of your stick values are properly centered. They all need to be EXACTLY at 1500 else you will see odds issues.


I fixed the centering issue with some calibration and a larger deadband. The GUI values are fixed, and in tests it seems more stable. But it's still not getting off the ground.

Cheezey
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Re: Motor power reducing

Post by Cheezey »

Dare I say... bump?

I just switched to a turnigy 9x since my ct6 died, but I'm still getting the same problems.

brewski
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Re: Motor power reducing

Post by brewski »

Boy are you having problems. I would have given up by now!
Have you tried good quality props (CF or Composite) & adapters plus accurately balanced them? Also have you set LPF filter (start with 43Hz) for your Gyro/ACC in Config.h? If using Atmega 2560 based FC use 4096 when doing EEProm Clear & then upload modified sketch.
I'm assuming you are running latest MW V2.3 or MW 2.3 Navi b7 if you have GPS & want advanced flight features together with matching WinGUI or MW Config for these versions.

Cheezey
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Re: Motor power reducing

Post by Cheezey »

brewski wrote:Boy are you having problems. I would have given up by now!

Well, I've spent a lot of time and money and I don't want that all to go to waste. Also, if I ever get it working, I can tell people it took 6 months because it was so amazing!

brewski wrote:Have you tried good quality props (CF or Composite) & adapters plus accurately balanced them?

Guess I should try!

brewski wrote: Also have you set LPF filter (start with 43Hz) for your Gyro/ACC in Config.h?

At 10hz it takes off a few inches, but isn't stable.

brewski wrote:If using Atmega 2560 based FC use 4096 when doing EEProm Clear & then upload modified sketch.

It's a 328.

brewski wrote: I'm assuming you are running latest MW V2.3 or MW 2.3 Navi b7 if you have GPS & want advanced flight features together with matching WinGUI or MW Config for these versions.

You are correct.

So, it looks like I need better props, as suggested by both you and the source code comment ("Use this only in extreme cases, rather change motors and/or props"). I guess I'll order some :|

brewski
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Re: Motor power reducing

Post by brewski »

You won't regret it.
When I first tested my X525 with the flimsy plastic props & adapters that didn't correctly centre, quad would hop around the yard. When I set 42Hz for MPU 6050 it would actually lift off but was lacking power & very unstable. A set of APC composite 10 x 5.5 with matching adapters sorted out the power loss & instability caused by vibrations & it's been flying well ever since with stock PIDS.

Cheezey
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Re: Motor power reducing

Post by Cheezey »

I'm having some trouble finding carbon props that will fit. All the ones in stock at HobbyKing are for 4mm or 8mm shafts, but I have my props attached to a 5mm threaded shaft.

Any suggestions for a place to find suitable props in the USA? I even checked eBay, but no luck.

brewski
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Re: Motor power reducing

Post by brewski »

I bought the APC Composite props & adapters from my local hobby shop. The composite are much cheaper than CF & very strong. The balance was also spot on.

mposchl
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Re: Motor power reducing

Post by mposchl »

Hi all,

I'm also new in multiwii, but I experience the same problems - if i put off all props, stable the model, connect to multiwii conf, arm it and give full throttle, all motors are approximately at full power according to the graphic in the mw gui...but in time, without doing anyting, some motors loose power (the indicators go down)...and it is not possible to power it up until I move the throttle stick down, motors stop and I give it full throttle again. Also, if I let the power down again and try pitch, yaw or roll, the motors (indicators) dont get back to previous state before i move the appropriate stick - is it normal? After all - when i try to fly, i usually get off the ground nicely (but from most videos i see on youtube it should be MUCH MUCH better), but i'm really not able to fly it, it just wobbles, falls down and even if i give full throttle, it doesnt lift...so it is a huge challenge to even hold it in the air... I had many suspisions - vibrations (i crashed and bent some of the shafts, but i changed to new motors), bad props (yes, i use cheap plastic ones, but i try to balance it as good as i can), i calibrated ESCS, gyro, acc...with no change. I am starting to be desperate :(. Should I really start tuning the PID? As I can see, very few people have to do this, most of them fly, at least in the beginning with factory PID and it flies nicely, smoothly...

It is HJ450 frame with mwc SE 2.5, it runs 2212/13T KV1000 cheap motors with 10x4.5 plastic props...particularly, it is the one kit from dx.com (www.dx.com/p/313508)

please, help, at least, where to start...i invested much money so far and still cant get it work at least "acceptably"

brewski
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Re: Motor power reducing

Post by brewski »

As in above vibration is your issue. Hold quad firmly from below & connect to MW Config using USB or better BT & EZ-GUI. Observe the sensor lines for ACC & Gyro as throttle is increased. You will also feel the vibrations directly in your hand. You must get the vibrations as low as possible as the ACC & Gyro will try to compensate for them & kill power as well as making quad unstable. When you have vibrations under control you can set MPU LPF filter to 42Hz & see how it flies.

mposchl
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Re: Motor power reducing

Post by mposchl »

ok, so i will wait for new motors and lets see what happens. also i try to do string tuning... anyway - i bought antivibation pad with silicone balls and put it under mwc, but there was really no change. Also - it doesnt change with and without props...so maybe really the PID is the key?

Cheezey
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Re: Motor power reducing

Post by Cheezey »

The new props really helped, it takes off now. But progress is slow because I haven't actually had a stable flight yet, both times it's tumbled through the air and broke something because I have no idea what I'm doing.

brewski
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Re: Motor power reducing

Post by brewski »

Even with good quality APC Composite or CF props you still need to balance them. Have you calibrated & trimmed your ACC & take off in Horizon mode?
You might like to read thru this guide I prepared on how to achieve successful first flight viewtopic.php?f=18&t=5363

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