electronics

[hellogoose]

Hi, I am just getting into the RC hobby and really need help with electronics!
Sooooo, I built my first foam trainer plane.....
It has a 40" wing span, 30" fuselage, 5" wing chord, weighs about 500g without electronics, supposed to be puller design
But I can not understand motor Kv and size; ESC amp rating ect. And planes need electronics to fly...
Can someone please check my understanding and answer my questions? Thanks sooo much in advance, and sorry about so many questions.

Motors
I understand that Kv is the constant of RPM? so if I have a high kv motor then I need a small prop that will have more speed but less thrust and vice versa.
I also understand that the motor size is how big the motor is and how much power it will draw?
What is max efficiency current in motor specs?

ESC
I know that the ESC has an amp rating, and if my motor's amp draw is higher than the ESC rating, it will explode and stuff...
How do I find out the amp draw of my setup in order the get the correct ESC?

Battery
I know that the cells are the little batteries that make up a pack, the higher the cell count, the more volts the pack will produce.
I know that the C rating is how fast you can charge the battery
I know that
How do I determine how many cell battery to use?

 

[Houndpup Rc]

Hi, I am just getting into the RC hobby and really need help with electronics!
Sooooo, I built my first foam trainer plane.....
It has a 40" wing span, 30" fuselage, 5" wing chord, weighs about 500g without electronics, supposed to be puller design
But I can not understand motor Kv and size; ESC amp rating ect. And planes need electronics to fly...
Can someone please check my understanding and answer my questions? Thanks sooo much in advance, and sorry about so many questions.

Motors
I understand that Kv is the constant of RPM? so if I have a high kv motor then I need a small prop that will have more speed but less thrust and vice versa.
I also understand that the motor size is how big the motor is and how much power it will draw?
What is max efficiency current in motor specs?

ESC
I know that the ESC has an amp rating, and if my motor's amp draw is higher than the ESC rating, it will explode and stuff...
How do I find out the amp draw of my setup in order the get the correct ESC?

Battery
I know that the cells are the little batteries that make up a pack, the higher the cell count, the more volts the pack will produce.
I know that the C rating is how fast you can charge the battery
I know that
How do I determine how many cell battery to use?

You got it just about 100%! So C rating is discharge and charge rates, the kv of a motor is how many rpm's you will get per a volt. 👍

Usually to see how many amps you motor will draw, a basic google search will pop that up or you can check the spec sheet for similar motors.👍

For your plane I recommend a 2218 1100kv motor or bigger with a 40-50a esc and probably 3-4s👍 If you have any other questions be sure to ask!

 

[hellogoose]

Thanks for the reply!!!!!!!
I did not expect such a quick reply
A question, how did you determine the motor, esc, and battery?

 

[Mr NCT]

The motor spec charts that Innov8tive Designs includes with their motors are a great resource for figuring out what motor, prop, battery and esc combo to use for your plane. They list thrusts for every combination which is really helpful. I don't work for them or benefit in any way, just a huge fan and customer because of how thorough and helpful they are. Here's an example of their charts:

https://innov8tivedesigns.com/images/specs/Cobra_2213-22_Specs.htm

 

[Mr NCT]

Oh, and it's not cheating to look at at a similar design and copy their motor/battery/esc set up.

 

[Bricks]

Motor and ESC determines what batteries can be used as far as cell count and at times prop size, this is where a Watt Meter comes in handy.

 

[Merv]

...I know that the C rating is how fast you can charge the battery...

NO, the C rating of a battery is for discharge ONLY. Never for charging.

You calculate the amp rating of a battery using this formula MAH/1000 x C
Example: a 2200 MAH 20C battery can safely supply 55 amps at whatever voltage the pack is. (2,200/1000 x 20 = 55)

Charging is completely different, if you were to charge that battery at 55 amps you would certainly cause a fire.
For LiPo's, I recommend charging at 1C, for a 2200 mah battery, that would be 2.2 amps.

 

[Houndpup Rc]

Thanks for the reply!!!!!!!
I did not expect such a quick reply
A question, how did you determine the motor, esc, and battery?

You kinda get to know after a while

 

[Houndpup Rc]

NO, the C rating of a battery is for discharge ONLY. Never for charging.

You calculate the amp rating of a battery using this formula MAH/1000 x C
Example: a 2200 MAH 20C battery can safely supply 55 amps at whatever voltage the pack is. (2,200/1000 x 20 = 55)

Charging is completely different, if you were to charge that battery at 55 amps you would certainly cause a fire.
For LiPo's, I recommend charging at 1C, for a 2200 mah battery, that would be 2.2 amps.

Argh, you are correct!😫😂👍 (Though I believe with higher C batteries you can charge at 2 or even 3C just its harder on your batteries)

 

[Houndpup Rc]

Thanks for the reply!!!!!!!
I did not expect such a quick reply
A question, how did you determine the motor, esc, and battery?

No prob!👍

 

[hellogoose]

Another question(s),
how does the cell count therefore the voltage relate to the other stuff?
Does it relate to the motor size?
(what is the motor size exactly?)
ESC amp rating?
The number of servos?
How do all these connect together?

 

[hellogoose]

Also, does the size of the servo matter?
Is a urm, uh...1.7g servo ok?

 

[Houndpup Rc]

Also, does the size of the servo matter?
Is a urm, uh...1.7g servo ok?

So for most 30-48" airplanes you will want 9g servos, I personally like these metal gear ones off amazon. They last WAY longer and are reasonably priced!

https://amzn.to/3LVq547

 

[Houndpup Rc]

Another question(s),
how does the cell count therefore the voltage relate to the other stuff?
Does it relate to the motor size?
(what is the motor size exactly?)
ESC amp rating?
The number of servos?
How do all these connect together?

So the ESC steps the voltage down to 5v for your receiver, servos, ect. The amperage of your ESC is usually marked on it with a label though pretty much all 20a+ will run 4 9g servos fine.

For how everything connects together your battery just plugs into your ESC, from their the power goes to your motor from your three wires on the ESC and your receiver is connected to the three wire plug coming from the esc, then all the servos, retracts ect plug into the receiver.

Hope this helps and if you have any more questions definitely ask! 👍

 

[hellogoose]

Thanks!
But if the BEC will step down the voltage to 5 volts why does the cell count matter?
Also, should I get 180 degree servo or 360?

 

[Houndpup Rc]

Thanks!
But if the BEC will step down the voltage to 5 volts why does the cell count matter?
Also, should I get 180 degree servo or 360?

It steps it down for the receiver and servos..The motor gets the full voltage👍

For rc airplanes 180 is good👍

 

[hellogoose]

OH!!!
Thanks for clarification, I UNDERSTAND NOW
thanks!!!

 

[Bricks]

After plugging in the ESC to the motor if it is running backwards just change two of the wires to reverse. When buying motors, batteries and ESC`s make sure the connectors are compatible.

 

[Merv]

...how does the cell count therefore the voltage relate to the other stuff?
Does it relate to the motor size?
(what is the motor size exactly?)

The battery voltage is one factor that determines how fast the motor spins. The other is Kv, that is revolutions per volt.

The faster a motor spins a prop, the more amps it will draw. To avoid overloading the motor, high kv motors will use smaller diameter props than the lower kv version.

The motor size, 2212 for example, refers to the size of the motor stator, 22 mm diameter & 12 mm long

ESC amp rating?

How many amps the ESC can provide. If the motor + servos draw more amps than the ESC is rated for, you will burn it out.

Don't cut it too close, it's good to have a little overhead. If the motor can draw 30 amps, use a 40 amp ESC.

The number of servos?

Each 9g servo draws about 3/4 of an amp at full load. With a BEC rated at 3 amps you can safely use 4 9g servos. You can use more servos provided you don't use more than 4 of them at one time or don't put all under full

 

[tamuct01]

You can also use eCalc (https://www.ecalc.ch/motorcalc.php) to help figure out your setup. There are a lot of variables, but you can experiment with various power setups and props to determine thrust, etc. The free version has a lot of common components and the paid version unlocks a ton more specific motors, ESCs, and props.