Hi, I'm new to the hobby and now planning for my first 250 mini quad.
I'm having some trouble trying to find the suitable motors, escs & battery.

To be clear, I'm not intested in any FPV or Aerial flying (so no cameras, VTx,...).
What I'm interested in is to learn about autonomous flying and & I'll also try to build and code my own flight controller from scratch!

What I want, is to build a basic quadcopter & get into the air quickly. Then, I'll modify my build by adding either:
- Pixracer kit or the
- Arduino Uno

So what I'm looking for is a build that has all the parts except for the FC to be quite durable so that I can reuse them later on.
Also I'm looking for a build that can handle additional weight, so a 3:1, 4:1 thrust:weight ratio is suitable for me I think. No more than that because I'm not looking for super high responsive acrobatic performance.

Following many guides & suggestions I found online, here's the build I'm planning:
- Emax Nighthawk 250 quad Frame                  181g (w screws)
- CC3D EVO                                                  15.2g (w box)
- 4x motors                                               4x 28.6g (I took the Emax RS 2205 S 2300Kv motors for weight reference)
- 4x ESCs                                                  4x     6g (I took the Racerstar RS30A for weight reference)
- Kingkong 5040 Props                                4x     6g
- Matek PDB w xt60 jack                                    11g
- 3S, 2200mAh                                                200g
- Battery alarm                                                   5g
- Receiver                                                          5g
------------------------------------------------------------------
- Total                                                            580g
- Total w wires & jacks                                     600g

So here's the math:
Total thrust = 600 x 3 = 1800 g
Thrust per motor = 1800 / 4 = 450 g

According to my frame, a 5-6 inch prop should be OK, I chose 5 inch for my build

There are many popular & good motors I've seen including:
- Racerstar BR2205 2300/2600kv motors which are rated around 800-1000 g thrust at 100% throttle
- Emax RS 2205 S 2300 kv motors which are rated up to 1400 g thrust at 100% throttle

As you can see, the thrust is way too high compare to what I wanted. However, I think I can still buy these good motors then try to limit the power by either:
- Lower my battery to 2S
- Use 4 inch props
- Limit the power in BLHelisuite?

These options are all weird I think. I don't know if it's even possible to do so! And then I'm not using what I've paid for

So what do you guys think? I'm getting stuck at the motor selection and can't move on to choosing ESC & battery (I need to know how much current)

I'm also considering motors like the Emax MT1806 2280KV or the MT2204 2300KV which have a much closer thrust rating to what I need. I'm just not sure which to choose. Please help.

Thank you in advanced

Having more power than you need is not something you should try to design out.

More power, even if the target application is autonomous flight, gives you better handling and is going to drive the motors at a more efficient part of the throttle range which will be kinder to your batteries and give you longer flight time.

The minimum thrust should be calculated at 50% throttle. If you take the thrust achieved by a motor/prop combination in a static thrust test, you should use 75% of what the thrust test shows as static thrust is not the same as dynamic thrust. At 50% throttle, the combined thrust of all four motors should be equal to, or preferably slightly higher than the all up weight of the craft.

The absolute minimum power to weight ratio for safe control of your craft is 2:1. Even better is 3:1 or even 4:1. If the craft is too quick, you can always tame it by changing flight controller settings but if the craft is underpowered, you can only fix that by changing the hardware or using a higher voltage battery.

(07-Jul-2017, 10:13 AM)unseen Wrote: Having more power than you need is not something you should try to design out.

More power, even if the target application is autonomous flight, gives you better handling and is going to drive the motors at a more efficient part of the throttle range which will be kinder to your batteries and give you longer flight time.

The minimum thrust should be calculated at 50% throttle. If you take the thrust achieved by a motor/prop combination in a static thrust test, you should use 75% of what the thrust test shows as static thrust is not the same as dynamic thrust. At 50% throttle, the combined thrust of all four motors should be equal to, or preferably slightly higher than the all up weight of the craft.

The absolute minimum power to weight ratio for safe control of your craft is 2:1. Even better is 3:1 or even 4:1. If the craft is too quick, you can always tame it by changing flight controller settings but if the craft is underpowered, you can only fix that by changing the hardware or using a higher voltage battery.

Thank you for your advises!

I find it a bit confusing when talking about the thrust of the motor.
People usually suggest look for the motors with the suitable thrust according to the calculated total thrust from the quad's weight.

Just to make sure... the motor's thrust people are talking about is the minimum thrust (at 50% throttle) or the maximum one (at 75% throttle in static tests)?

75% of the static thrust at 50% throttle multiplied by the number of motors must equal or exceed the all up weight of the craft.

This is the absolute minimum thrust needed to safely control the craft.

If you based the calculation on the thrust achieved at 100% throttle, there would be nothing left to fly the craft with. Remember that a quad achieves directional control by using differential thrust. If the motors are already running at 100%, differential thrust cannot be created without losing overall thrust and the craft will fall out of the air.

I know that's not what you were asking, but i see the cc3d evo (not revo) in your list which is an (outdated) F1 board... You should be able to get an F3 or even F4 FC for the same money.

Cheap250 (which I built as a 1st build to play with autonomous stuff with an APM) uses Emax 2204 and 5040ish props.

Doesn't have too much thrust, the same props on my UAFutures 210mm with the Racerstar 2205 motors doesn't have too much thrust.

Just use the Racerstars and enjoy the savings compared to a lot of "racing" motors

fftunes Wrote:I know that's not what you were asking, but i see the cc3d evo (not revo) in your list which is an (outdated) F1 board... You should be able to get an F3 or even F4 FC for the same money.

Can you suggest some good ones for the same money? I'll see if I can get those
Sorry, to honest the reason why I chose CC3D is because it's widely available around my place XD

Aaron Wrote:Cheap250 (which I built as a 1st build to play with autonomous stuff with an APM) uses Emax 2204 and 5040ish props.

Doesn't have too much thrust, the same props on my UAFutures 210mm with the Racerstar 2205 motors doesn't have too much thrust.

Just use the Racerstars and enjoy the savings compared to a lot of "racing" motors

Thank you for sharing your experience Aaron! I'm going for the racerstar now with much more confidence! Maybe I'll even the Emax RS 2205 S motors if possible.

Phong, I'm pretty sure www.myrcmart.com had some SPRacing F3 EVOs going for very good prices. I paid under USD15 delivered for the last one I bought from them.

(10-Jul-2017, 06:09 AM)Aaron Wrote: Phong, I'm pretty sure www.myrcmart.com had some SPRacing F3 EVOs going for very good prices.  I paid under USD15 delivered for the last one I bought from them.

Is this the correct one? It seems to have less ports than the ones sold on Banggood.

EDIT: Sorry, I've mistaken it for the SPRacing F3 without the "EVO".

Btw, after researching a bit more, I think I'd like to:
- do in-flight pid tuning either through my Transmitter or Laptop
- Read current sensor values on my Transmitter/Laptop while flying and having the peak current value after flight is great

I'm planning to use the Flysky transmitter i6X (10 channels) and do no FPV (so no OSD I think )

So in the end, maybe buying a better FC will be a better option than adding sensors and telemetry stuffs to the cheap CC3D

Any suggestion for another FC that is suitable?

I'm using F4 revo clones for ~17$ but it doesn't have current sensor i think... Aaron's tipp for the SPRacing F3 EVO is pretty good i'd say, i think it should do everything you want?

I never used telemetry stuff though so i'm not sure if (and how) feeding back current values to transmitter is possible... However you could always log them and check log files after flight (i think SPRacing uses a micro SD card for that).

Hmm, I think I've found the suitable tool for the current sensing which is the Eagle tree E-logger... quite expensive though so I'm not sure if I'm going for it.

I'm quite confused about the SPRacing F3 actually, why is most of the products in myrcmart says "for Clean flight"
You can find them in the middle of this page: link

Correct me if I'm wrong, but according to what I read, the F3 board is for Betaflight and the F3 EVO board is for Cleanflight.
So why are some of the links showing non-EVO version but still say it's for cleanflight?

To be honest, I'm quite off topic now asking about flight controller, and I think I'll ignore the current sensing part as it'll only boost the price up significantly

What I'm really worrying now is about my FC, because most ESCs nowadays use BLHeli_S & aim for "active breaking" with Dshot600 or sth. But as far as I know, the cc3d doesn't support dshot. So I'll be either getting a better FC, or older ESCs now

Arghh, such a mess I'm in right now, sorry to drag you guys into this too

What about a FC with pdb and current sensor built in or separate? Here is a list of some:
Omnibus f3/f4
Matek f4 FC and separate pdb
Matek f4 FC with built in pdb
Betaflight f3
Dys F4


All of these fcs can run betaflight or cleanflight as far as I know

(10-Jul-2017, 01:13 PM)oyvinla Wrote: All of these fcs can run betaflight or cleanflight as far as I know

Same for the SPRacing btw. Don't let shop descriptions confuse you.
Another detail about the SPRacing - if, then choose an EVO version (means it has SPI gyro connection, much faster/better).

And all in all, even if you hadn't planned to use dshot, i would advise for a better FC (F3 or F4) to begin with. F1 boards will officially not be supported anymore by betaflight in the near future...

(10-Jul-2017, 01:13 PM)oyvinla Wrote: What about a FC with pdb and current sensor built in or separate? Here is a list of some:
Omnibus f3/f4
Matek f4 FC and separate pdb
Matek f4 FC with built in pdb
Betaflight f3
Dys F4


All of these fcs can run betaflight or cleanflight as far as I know

Thank you for your suggestions, those boards looks great    but I don't have much experience now so for me to understand all of those features and use them might take me a while 

Correct me if I'm wrong, most of these boards either are Matek or Omnibus so they're built to display the pid parameters and current ratings on the OSD

I actually don't do FPV so maybe my only option is to use their blackbox to read those numbers after flight.

So I think I'll save myself a headache and skip those current sensing part, I can still tune my pids anw.

In term of flight controller, focusing on the price, the simplicity of the design (for a noob like me to understand and make use of the board), what options are there for me?

A CC3D is perfect for both the price & simplicity, but it's a bit out dated though

(10-Jul-2017, 03:45 PM)fftunes Wrote: Same for the SPRacing btw. Don't let shop descriptions confuse you.
Another detail about the SPRacing - if, then choose an EVO version (means it has SPI gyro connection, much faster/better).

And all in all, even if you hadn't planned to use dshot, i would advise for a better FC (F3 or F4) to begin with. F1 boards will officially not be supported anymore by betaflight in the near future...

Yeah, SPRacing F3 EVO looks great, I'm leaning towards those now ... unless you guys some up with even better options