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Old Jun 06, 2015, 03:02 PM
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Help!
Controlling brushless motor/ESC with Arduino

Hello everybody! I need your help. Desperately.
I have real trouble making this combination work. I have some knowledge/experience with this, but feel free to explain me like I'm five.
So I bought this pack: http://www.dx.com/p/a1504-2700kv-bru...4#.VXMrJ9Kqqko
And this battery: http://www.dx.com/p/11-1v-1200mah-li...7#.VXMq3NKqqko
After this combination did not work, somebody told me to try with 2S battery, so I took this one: http://www.dx.com/p/zop-7-4v-1300mah...7#.VXMqw9Kqqko
I also tried this ESC: http://www.dx.com/p/mystery-speed-co...icopters-34338
I use this code for arduino: http://www.instructables.com/id/ESC-...Upload-sketch/
Problem that I am experiencing is that motor/prop does not produce enough static trust of ~250g. I have calculated it here: http://adamone.rchomepage.com/calc_thrust.htm
While I change input value to ESC (700-2000), motor speeds up, but it stops somewhere around 1400. After 1400 it just rotate with same speed. Without prop it stops somewhere around 1700. And static thrust it produce is negligible.
I don't have anybody to ask in person, so I was trying to fix this for half year alone using just tutorials on the internet. Now I don't have any other ideas, so please help me.
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Old Jun 06, 2015, 09:14 PM
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Most ESC's require a "calibration" routine be done at least once. Some need it every time they power up. The calibration sets the ESC to recognize the range of signal that is being sent to it. The standard signal range is 1000 to 2000 microseconds. They also require a startup routine that usually has the signal at the 1000 microsecond level when the ESC is powered up. Your control program for the ESC will have to take these requirements into account.

As far as how much power you are getting from the motor, you have a rather small motor so you will not get a lot of thrust out of it. There are probably little or no specifications as to what the maximum current and what voltage you are supposed to run the motor with the "shaft" provided in the package. (BTW most people call that "Shaft" a propellor).

If you were to tell us what you want to accomplish with the motor and prop we could recommend a setup that would get you there.
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Old Jun 07, 2015, 05:30 AM
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With prop/shaft:
I tried what you described, but behavior is the same. Signal is on 1000, I connect the battery, motor play one long beep as usual, I change signal to 1200, motor start running, I change signal to 1400, motor speeds up but now I can hear how it is not working well. It's struggling. Speed is varying up and down. Then I set signal to 1600, nothing changes. Then to 1800, nothing changes for a second, then motor stops.
Without prop/shaft:
Same situation, but motor does not stop at 1800. It is still running as on 1400 and struggling. It can go like that to 2000.

btw. Battery is new and full (7.4V, 1300mAh, 2s, 20C, measuring with multimeter it says 7.6V, at the moment when motor stops with prop it is 7.49V).

Can you tell me how much static thrust can I expect from this combination I'm using? Maybe I do not enter right data in the calculator and I get wrong result.

Regarding what I want to accomplish.. Well I just wanted to learn how to make an airplane. I was learning from many different tutorials and everything about RC airplanes, but I wanted to do it myself. Not by following some already defined tutorial, step by step. So I decided to start wit this pack I mentioned in the first post, but from that point, noting is going as planned
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Old Jun 07, 2015, 07:28 AM
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I'd suggest you get a wattmeter and measure the voltage and current when running. Another approach would be to try it with the ESC driven by a receiver or servo tester to see what happens when a known standard signal is used instead of your untested software.

But if your battery is only measuring 7.6V with no load on it then it isn't fully charged. A fully charged battery should be 8.4V with no load. What are you using to charge it ?

Steve
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Old Jun 07, 2015, 07:40 AM
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1. As mentioned, a fully charged 2S battery reads 8.4V

2. Motor manufacturers and sellers tell tall tales about the performance of their motors.
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Old Jun 07, 2015, 08:29 AM
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Maybe it is the calibration scheme in the firmware not being satisfied with you dealing with the safety and calibration requirements.

Try this for a common calibration scheme,

1 - Set the throttle device to about 3/4 throttle (1200-1300 or so should work) and then applying power to the ESC? The motor should not run because of safety considerations in the firmware programming.

2 - Give it a few seconds, if you get one beep, advance it to full throttle and wait for another beep or two, That is what gives the ESC the full throttle rate setting and signals to give it zero throttle

3 - Reduce to zero throttle and the ESC should give more beeps and arm . The number of beeps usually will relate the voltage to a number of LiPO cells (12V = 3S = 3 beeps, 8V = 2S two beeps, etc.).

Jack
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Old Jun 07, 2015, 01:20 PM
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Huh.. that's shame on me that I didn't checked what voltage should be for full battery. Upon arriving (I order batteries online) I just gave them to my assistant at faculty to charge them for me, because I don't have a charger for LiPo. He just returned them to me and said they are full. I'm talking about 2S and 3S batteries I mentioned in the first post. So I assumed they are full.
Regarding power supply, I have also tried using power supply from PC (12V) and car battery (also 12V). Same results.

Another approach would be to try it with the ESC driven by a receiver or servo tester to see what happens when a known standard signal is used instead of your untested software
That would be great, but unfortunately I don't have such equipment. And I don't know anybody in may area who might have it.

Motor manufacturers and sellers tell tall tales about the performance of their motors
If we take in account that motor is bought online, that might me true as well.

@jackerbes
I did what you told me, and here are results:
1) on 1300 at powering on the ESC I get beep. I would say that it is the same beep I get on 1000. It arms immediately.
2) When I set to 2000, motor start running, then stops after couple spins. If I set to 1900 it do the same, but then enter programming mode.
3) Didn't get here
Repeated the procedure with other ESC (mentioned in first post), same results.
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Old Jun 07, 2015, 03:08 PM
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Jack
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So that routine does not work for you ESC, there was no guarantee that it would...

Here is the manual for the Mystery 30A ESC:

http://www.hobbyking.com/hobbyking/s...6X63807X15.pdf

Here is a servo tester that also displays the PWM rate, it can be used for a throttle. If your ESC has power on the BEC/Throttle lead it will power the tester, if not you can supply external power to the tester:

http://www.dx.com/p/hj-digital-servo...icopter-194793

The specs and instructions (such as they are) for using the HJ tester are on the DX page...

"..While I change input value to ESC (700-2000), motor speeds up, but it stops somewhere around 1400. After 1400 it just rotate with same speed. Without prop it stops somewhere around 1700. And static thrust it produce is negligible...."

That sounds like it is working right and normally. It should be starting somewhere around 1000 or so and be at full throttle at1500 or so. The ESC I use for testing starts a motor at 980 and is at full throttle at 1460 for example. And it is the same every time as long as I use the same procedure to start up and calibrate the ESC.

You have a 2700 Kv motor, a charged and rested 3S pack will be at about 12.3V (4.1V per cell) if your run a no load test (full throttle with no prop on) you would have an RPM of about 2700 x 12.3 = 33,210 RPM.

With a prop on and at the continuous rating it would normally be at about 75% of the no load RPM. At full throttle it would be at about 90% and that would be time limited due to eventual overheating.

75% = 24,907 RPM
90% = 29,889 RPM

You have, I think, 4.1 x 4.1 prop. I think it is this one:

EMP 4.1x4.1 - www.flybrushless.com/prop/view/290

Static testing shows that prop at 25.000 RPM to be good for a little over 400g of thrust. And looking the the input power for 25,000 RPM that appears to be about 200W or a little more may be. You can study the various motors to refine that but the input power at a given RPM will be about the same with any motor unless there is a pretty bad Kv to voltage mismatch.

You motor is a 16g motor as near as I can tell, I can't find any specs for that say that but this looks like it may be the same motor (the Suppo A1510):

Suppo - A1510 - www.flybrushless.com/motor/view/452

If it 16g it will handle about 2.5-3W per gram at it's continuous rating and when it gets up to 4W or so it will over heat probably. You can look at the test data there with similar sized props but your prop was not tested with it. The GWS 4.5 x 4 is a similar prop and it pulled this on 3S so it might be a reasonable expectation for your 4.1 x 4.1 prop:

GWS HD 4.5x4
10.9V
6A
65W
16950 RPM
Pitch Speed: 61 MPH
Thrust 261g 9.21 OZ.
RPM as % of Kv*V: 70%

If your motor is the Suppo 16g motor (it was sold under a number of names and brands) the 3W per gram or 48W is reasonable expectation for an input power. That would be loads that draw about 4A on 3S (12V) or 6A on 2S (8V).

Everyone needs a watt meter in this hobby unless you are just going to buy and fly without any further experimentation or curiosity as to what is going on.

I think some of your questions are answered here, I still don't if or why you are having trouble getting the motor and ESC to pair up normally and work right...

Jack
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Old Jun 07, 2015, 06:07 PM
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@jackerbes
Thank you very much for such detailed explanation and that you spend your time to write it. I read it twice and some things are more clear to me. For example, I didn't know that RPM at full throttle is different with and without prop. Which actually makes sense...
Anyway, I think I solved one problem. I removed connectors on motor and ESC-s and soldered connection directly. Now I'm getting around 100g of thrust at 70%. It is measured using approximate method, because I don't have balance at place right now. But let's say that's ok. At full throttle I think I get voltage cutoff, because voltage drops under 6.8V. Also, struggling is not present anymore.
So I would say that all this mess was produced by one (or more) bad connector.
Anyway, thank you very much for your time and help! I hope that when I charge my batteries that I'll be able to proceed to next step of making my airplane, and that I will present you here my toy
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Old Jun 07, 2015, 06:40 PM
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Jack
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Quote:
Originally Posted by biserx View Post
@jackerbes
Thank you very much for such detailed explanation and that you spend your time to write it. I read it twice and some things are more clear to me. For example, I didn't know that RPM at full throttle is different with and without prop. Which actually makes sense...
Anyway, I think I solved one problem. I removed connectors on motor and ESC-s and soldered connection directly. Now I'm getting around 100g of thrust at 70%. It is measured using approximate method, because I don't have balance at place right now. But let's say that's ok. At full throttle I think I get voltage cutoff, because voltage drops under 6.8V. Also, struggling is not present anymore.
So you are using 2S and not 3S? That changes all of the number of course. Here it is again corrected for 2S.

Your charged and rested 2S pack will be at about 8.2V (4.1V per cell) if your run a no load test (full throttle with no prop on) you would have an RPM of about 2700 x 8.2 = 22,140 RPM.

With a prop on and at the continuous rating it would normally be at about 75% of the no load RPM. At full throttle it would be at about 90% and that would be time limited due to eventual overheating.

75% = 16,605 RPM
90% = 19,926 RPM

Now we can use this thrust calculator to see the thrust at those RPM estimates:

http://www.flybrushless.com/tools/thrustCalc

75% = 16,605 RPM = 184g
90% = 19,926 RPM = 267g

So that is what you can look forward to for thrust on 2S with that prop (if it is the prop you have).

Quote:
So I would say that all this mess was produced by one (or more) bad connector.
Anyway, thank you very much for your time and help! I hope that when I charge my batteries that I'll be able to proceed to next step of making my airplane, and that I will present you here my toy
Bad connectors happen all the time, you have to be able to solder or learn to do it better. It is best have connectors and for your small motors I would recommend 2mm or 3.5mm bullet connectors. The 2mm connectors would be my first choice.

When I solder bullet connectors on I use a toothpick and put a very light smear of Oatey's No. 5 lead free paste flux[/URL] inside the wire socket and then fill the socket about half way up with solder. Then I tin the stripped end of the wire, using the flux again usually, and remelt the solder in the socket and plug the wire into it letting it get hot enough for the solder to flow on the wire.

Let it cool and pull on it hard, if you don't have a good connection it might come off but I have have them come off when I use the flux and do it that way.

Are you in the U.S.? I
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Old Jun 07, 2015, 06:43 PM
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Jack
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Quote:
Originally Posted by biserx View Post
@jackerbes
Thank you very much for such detailed explanation and that you spend your time to write it. I read it twice and some things are more clear to me. For example, I didn't know that RPM at full throttle is different with and without prop. Which actually makes sense...
Anyway, I think I solved one problem. I removed connectors on motor and ESC-s and soldered connection directly. Now I'm getting around 100g of thrust at 70%. It is measured using approximate method, because I don't have balance at place right now. But let's say that's ok. At full throttle I think I get voltage cutoff, because voltage drops under 6.8V. Also, struggling is not present anymore.
So you are using 2S and not 3S? That changes all of the numbers of course. Here it is again corrected for 2S.

Your charged and rested 2S pack will be at about 8.2V (4.1V per cell) if your run a no load test (full throttle with no prop on) you would have an RPM of about 2700 x 8.2 = 22,140 RPM.

With a prop on and at the continuous rating it would normally be at about 75% of the no load RPM. At full throttle it would be at about 90% and that would be time limited due to eventual overheating.

75% = 16,605 RPM
90% = 19,926 RPM

Now we can use this thrust calculator to see the thrust for that prop at those RPM estimates:

http://www.flybrushless.com/tools/thrustCalc

75% = 16,605 RPM = 184g
90% = 19,926 RPM = 267g

So that is what you can look forward to for thrust on 2S with that prop (if it is the prop you have).

Quote:
So I would say that all this mess was produced by one (or more) bad connector.
Anyway, thank you very much for your time and help! I hope that when I charge my batteries that I'll be able to proceed to next step of making my airplane, and that I will present you here my toy
Bad connectors happen all the time, you have to be able to solder or learn to do it better. It is best have connectors and for your small motors I would recommend 2mm or 3.5mm bullet connectors. The 2mm connectors would be my first choice.

When I solder bullet connectors on I use a toothpick and put a very light smear of Oatey's No. 5 lead free paste flux[/URL] inside the wire socket and then fill the socket about half way up with solder. Then I tin the stripped end of the wire, using the flux again usually, and remelt the solder in the socket and plug the wire into it letting it get hot enough for the solder to flow on the wire.

Let it cool and pull on it hard, if you don't have a good connection it might come off but I have have them come off when I use the flux and do it that way.

Are you in the U.S.? It makes a difference on the materials you can find and use. You can edit your profile to tell us where you are and that will get you better help from people that know your area.

Have you picked a plane? Will you build with foam? I may know good plan for you.

Jack
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Old Jun 08, 2015, 04:08 AM
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Well, I have 2S and 3S, and I will probably use 3S to get more thrust. I just had connected 2S to the system, so I tested and measured with it.
But I got the way how to calculate thrust from your post, so now I would know to calculate thrust for any battery.

Regarding connectors, I learned the hard way that it is important which connectors are used. I had some old connectors, not bullet connectors. Now I will order those you recommended.

And I am not from U.S. Unfortunately. I am from Serbia and for me, the most accessible way to get components is to order them on dx or aliexpress and wait month for them to arrive by post.

Regarding the plane, I did not done that yet. I was just testing the electronics and trying to confirm calculated thrust, so after that I can have input data which I can use to plan the airplane (dimensions, materials etc).
But anyway, I'm planning to make flying wing or something like skysurfer but smaller ofc.
And I am open for any suggestions
Edit: Yes, I would use foam to build plane.
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Old Jun 08, 2015, 08:01 AM
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Jack
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Pusher designs with the motor on a pylon are a waste of time in my opinion. The prop size is limited and the pylon adds a lot of drag to the glide.

For a high wing trainer the BB 24 would be a good choice, that has been built as light as 50 grams or so I think. Look for the plans in the list here:

** Blu-Baby Primary Trainer ** Plans, Pics and Fun! - http://www.rcgroups.com/forums/showthread.php?t=681556

Look for the KFm2 wing plan for the BB 24, that will be better than the under cambered wing, especially if you want to fly it outdoors and have it handle a little wind.

Scale this KFm3P wing down to 24" or so and it will make a flat wing with a strong center section and that is a very nice flyiing wing too. Does good on a RET trainer and if you add ailerons later that works well too, much better than if you add ailerons to a wing with dihedral at the center joint.

Building a 32" KFm3 Flat Wing w/Ailerons - http://www.rcgroups.com/forums/showthread.php?t=1335888

For a flying wing I like the Divinity design the best, it can be scaled up or down easily and is a wonderful flyer. Easy to build and easy to fly too. Even a newbie could handle it with a luck if it was trimmed out right and the control inputs were tamed down a little at first. Or if the newbie were a very patient newbie and did not let his emotions get the better of himself.

The Divinity was originally built as a 42" wing but it was also scaled down to 32" and a few other sizes. the thread is here and if you look at the attachments in the thread from the Thread Tools link you can find the other sizes and plans:

http://www.rcgroups.com/forums/showthread.php?t=1023254

The dimensions (in Inches) for the 32" version are here:

http://www.rcgroups.com/forums/showa...4&d=1240690993

This post is the starting post of five posts with my build of the 42" version made with 1/4" (6mm) foam:

http://www.rcgroups.com/forums/showp...&postcount=322

Enter the thread there with the yellow link at the top right corner.

You can see some photos of my build on the 32" version at this link, I used 3mm foam for that and Nylon strapping tape for spars and the finished bare wing only weighed 98g without the motor or electronics on it. So your 16g motor should fly it well. A thrust to weight ratio will give you a very acrobatic capable plane, it only takes about 0.5:1 to get a stable flyer.

http://www.rcgroups.com/forums/showp...&postcount=558

Jack
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Old Jun 11, 2015, 03:28 AM
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jack, you made me owe you a beer

I was looking these designs you posted and I think I'll go with Divinity. I really liked your one on the thread you posted.
And I think I'll make the wing while I wait for my lipo charger to arrive. I'll keep you posted as I make the progress
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Old Jun 11, 2015, 05:16 AM
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Jack
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The 32" Divinity will be a great choice. It is small and light so it will be very responsive to control inputs.

I fly with kind of a heavy hand and tend to over do it on the controls. For the Divinity 32 I found that having about 1/4" or 6mm of up and down deflection on the elevons gave me all the control I wanted or needed for normal flight.

It is good to set up your TX so that you have some exponential to soften the response a little at the stick's center position. And also to use dual rates so that you have the 1/4" travel for relaxed flying and can also go to high rates to get really small loops and abrupt maneuvers.

Good luck with it

Jack
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