Solved Newbie with electronics trouble

[Adam F]

Hey! I'm trying to get back into the hobby, but I'm a bit stuck. When I give it any throttle my motor starts spasming (rapidly alternating directions and making a buzzing/ticking sound), or won't work at all. All my servos respond, though. I'm guessing it's that one of the wires connecting the ESC and motor isn't conducting. There's no pattern to working/not when I try jiggling the connections, so I'm pretty sure it's not that they're loose. I've only got this setup, so I can't test if it's a faulty ESC or motor by switching one out. A few questions: a) do you think my guess is correct? b) if so, should I replace all the wires out of the ESC to the motor, or is there a better course of action? c) if I try replacing those and it doesn't resolve the problem should I buy a new motor, or is there something else I can do? Thanks!

 

[quorneng]

Adam F
It might help is you can give some details of the motor, the ESC, the battery and how it is being controlled.
Normally motors and ESCs are very reliable "out of the box" provided the battery voltage being used is within the ESC's specification. Always remove the prop when testing a motor.

However if you are absolutely certain the ESC to motor connections are "good" then the likely hood is either the ESC or the motor has failed.
Unfortunately there is no practical way of repairing either so the only way of finding out which is bad is to replace one, usually the ESC . If the motor still oscillates with the new ESC good then the motor has to be replaced. At least you will then have a spare "good" ESC!

Be aware that when a motor oscillates as you show the ESC is actually delivering full power pulses down each wire in turn. Leave it pulsing for too long and the ESC will overheat and fail even if it was actually good to start with!

 

[LitterBug]

It also would not hurt to make sure the screws you are using to mount the motor are not so long that they are contacting the motor windings.

As Mentioned above, please provide pictures of your setup.

LB

 

[Adam F]

Components are from the old version of the FT power pack A kit and a 2s 1800mAh 35C battery. As you can see, the insulation on the ESC is in a rough way (cat got to it, somehow ), but the wires themselves seem intact. Interestingly at one point one of the wire pairs disconnected but the motor kept oscillating.

It also would not hurt to make sure the screws you are using to mount the motor are not so long that they are contacting the motor windings.

Checked this, but it's not the problem. Thanks for the suggestion.

Be aware that when a motor oscillates as you show the ESC is actually delivering full power pulses down each wire in turn. Leave it pulsing for too long and the ESC will overheat and fail even if it was actually good to start with!

Good to know! Thanks. I figured it would probably be best to limit how much I was running it as is.

Thanks for the help!

 

[Merv]

... should I replace all the wires out of the ESC to the motor, or is there a better course of action?...

First remove the prop. You don't want it starting unexpectedly.

Try unplugging one of the 3 wires between the motor & ESC, then run the motor. If there is no change, that's the wire with the problem. If there is a change, that wire is OK, plug it back in and try the next one. Gently tug on the bullet connectors, they can look OK, but one with a bad solder joint will come off when pulled. Next try gently tugging on the wires, a broken wire will stretch a bit. If all the wires check out, it most likely a bad ESC.

Today I had a motor quit on me mid air. Tomorrow I'm going to troubleshoot it using these steps.

 

[Adam F]

First remove the prop. You don't want it starting unexpectedly.

Try unplugging one of the 3 wires between the motor & ESC, then run the motor. If there is no change, that's the wire with the problem. If there is a change, that wire is OK, plug it back in and try the next one. Gently tug on the bullet connectors, they can look OK, but one with a bad solder joint will come off when pulled. Next try gently tugging on the wires, a broken wire will stretch a bit. If all the wires check out, it most likely a bad ESC.

Today I had a motor quit on me mid air. Tomorrow I'm going to troubleshoot it using these steps.

This is very helpful. Thanks for the step-by-step.

 

[Merv]

Update

I did my gentle tug test this morning & one of the ESC wires just fell off into my hand. For me it's a easy fix to solder it back on.

 

[AIRFORGE]

Update

I did my gentle tug test this morning & one of the ESC wires just fell off into my hand. For me it's a easy fix to solder it back on.

View attachment 256673

"Tug Test". Preventing pilots from having to share their insurance information since way back when.

 

[quorneng]

Your picture shows the motor and ESC (I note the uninsulated solder joints on the motor wires!) but what is controlling the ESC via the black servo plug?
The ESC needs a speed control mechanism to work. It can be a receiver driven from a transmitter or simply use a servo tester, like this setup I use for bench testing motors.

Note I use simple screw connectors to temporarily join the wires. Just a instantaneous short circuit "touch" of bare motor wires when under power can "fry" an ESC.

 

[Adam F]

Your picture shows the motor and ESC (I note the uninsulated solder joints on the motor wires!) but what is controlling the ESC via the black servo plug?
The ESC needs a speed control mechanism to work. It can be a receiver driven from a transmitter or simply use a servo tester, like this setup I use for bench testing motors.

Note I use simple screw connectors to temporarily join the wires. Just a instantaneous short circuit "touch" of bare motor wires when under power can "fry" an ESC.

Yeah, the bullet connector pins broke so I cut them all off and am just really careful not to bridge any. I won't fly it like this, just easier for testing. I haven't seen those screw connectors before, I should get some. The ESC is plugged into a receiver.

 

[Adam F]

I've done some testing and watched some troubleshooting videos and am pretty sure it's just the ESC output wires, and the ESC electronics and motor are fine. Suggestions on where to get new wire and bullet connectors to solder on? Are eBay/Amazon going to be my best bet, or is there somewhere cheaper? What rating/gauge wire should I get?

Thanks, all, for your patience answering basic questions.

 

[Merv]

... Suggestions on where to get new wire and bullet connectors to solder on? Are eBay/Amazon going to be my best bet...

That depends on where you are at. If you have a local hobby shop, I'd support it. If you are like me, with out a hobby shop anywhere close, and want it quickly, then yes, eBay or Amazon. The Chinese vendors will be cheaper but it takes 2-3 weeks to get stuff. If you are replenishing inventory, this is not a problem.

 

[Adam F]

That depends on where you are at. If you have a local hobby shop, I'd support it. If you are like me, with out a hobby shop anywhere close, and want it quickly, then yes, eBay or Amazon. The Chinese vendors will be cheaper but it takes 2-3 weeks to get stuff. If you are replenishing inventory, this is not a problem.

I'm also without a local shop. Is quality often an issue with generic vendors that I'd be better off with somewhere else? I've heard a bit about BuddyRC, GetFPV, Tot's, etc. and not sure if these are significantly more reliable?

 

[quorneng]

Looking closely at the picture of your ESC I am a bit concerned with the state of the motor wires where marked.

A brushless ESC has very sophisticated electronics. On starting it sends a pulse down a pair of wires at random. This makes the motor jerk. That motor motion causes a minute voltage to be generated down the third wire. From the polarity of that voltage the ESC works out which way the motor has turned and then sends the next pulse down the correct pair of wires to continue, or reverse, the direction of rotation. It does all this in a micro second.
If for any reason like a broken or a higher resistance "poor" connection it is unable to properly "read" that tiny third wire voltage then after a fraction of a second it simply sends a pulse again, hence your motor oscillation.
The connections to the motor have to be really good as when the motor is running a full speed it has to "read" that voltage over a hundred times a second in which ever wire is not carrying the main power pulse!

I would strongly suggest getting a replacement ESC to see if that cures the problem.

 

[Adam F]

Looking closely at the picture of your ESC I am a bit concerned with the state of the motor wires where marked.
View attachment 256730
A brushless ESC has very sophisticated electronics. On starting it sends a pulse down a pair of wires at random. This makes the motor jerk. That motor motion causes a minute voltage to be generated down the third wire. From the polarity of that voltage the ESC works out which way the motor has turned and then sends the next pulse down the correct pair of wires to continue, or reverse, the direction of rotation. It does all this in a micro second.
If for any reason like a broken or a higher resistance "poor" connection it is unable to properly "read" that tiny third wire voltage then after a fraction of a second it simply sends a pulse again, hence your motor oscillation.
The connections to the motor have to be really good as when the motor is running a full speed it has to "read" that voltage over a hundred of times a second in which ever wire is not carrying the main power pulse!

I would strongly suggest getting a replacement ESC to see if that cures the problem.

Fascinating, I had no idea. I assumed as long as there was a fairly intact connection it would be good enough. Ok, I was hoping hold off on getting a new ESC since I don't have a large budget, but it seems like it might be necessary after all. Thank you.

 

[Merv]

...Is quality often an issue with generic vendors that I'd be better off with somewhere else?...

I use the cheep stuff for the most part. All of my flying buddies use the name brand stuff. My stuff fails at about the same rate as theirs. I can't say there is any quality difference. There is a huge difference is service. My buddies all get a lot of free replacement parts. I just chuck the busted part and grab another from my supply bag.

If I'm buying something expensive like a Tx, I'll stick with a known supplier. But cheep stuff, like servos or connectors, I get from a generic supplier.

 

[Mr NCT]

There is a huge difference is service. My buddies all get a lot of free replacement parts.

That's my experience, too. I bought a name brand esc that the second time I used it (still on the bench to set control throws) the bec bit the dust. I got a mild lecture when I called the supplier but they sent me a new esc at no charge and they covered the shipping.

 

[Bricks]

For foamies I buy the cheapest I can find and like Merv said chuck them if they go bad.

 

[Adam F]

Ok, I know this is digressing a bit, but if I am getting a new ESC and bullet plugs with shipping it’ll be about the same price as a cheap A2212 motor/ESC combo that would save me some soldering. Would an A2212 1400KV be way out of scale for a Tiny Trainer (the only plane in my hangar as of yet)? The 2212 is about 50g, so over double the 23g 1806 motor that comes with Power Pack A, and of course way more powerful.

 

[Merv]

...Would an A2212 1400KV be way out of scale for a Tiny Trainer...

It will be fine, the 1400 kv will work, it will be a little fast. If I had a choice, I'd go with a lower kv, say something around 1000kv. I like the 2212 in the simple cub.