Understanding - (QuadCopter) Inputs & Electronics

Nov8er

Member
Hello to all. I want to start out by saying I'm really new to the community and very interested in quad and multi-rotor drones. I've decided to start from the ground and work my way up. First, I really need to learn the basics of the electronics such as: flight controllers, regulators and other things which I have little knowledge of. The most confusing to me is the compatibility of voltage throughout the whole system and into the receiver. I don't really need batteries jump frying over electric discharge. That would not be good for my budget lol. To be a little more simple I need some info on all the things I would need, other than a frame, to complete the electronics and have them all compatible.

Here are some quick objectives from my knowledge I need some advice on:
- I'm wanting to make a custom racer/multipurpose quadcopter
- Lasting battery 15-20 min preferably.
- cc3d flight controller compatible.
- fast motors.
- cc3d compatible speed controllers.
- A user friendly radio and receiver.
FPV setup will be later on, I need to get a drone airborne for now. Thanks and any help is very much appreciated.
 

Carapau

Tek care, lambs ont road, MRF Moderator
Voltage is relatively simple in principle. The batteries power the motors via the ESC (electronic speed controllers) directly. This voltage would normally be too much for the flight controller, receiver and other stuff so there are a couple of things that will bring the voltage down. Firstly flight controllers often come with their own voltage regulator making this bit straight forward and normally, receivers plug directly into the flight controller which is where they also get their power from so there shouldn't be any need for a separate regulator for the receiver. Secondly, if you have other kit that needs a lower voltage then a BEC is used. BEC stands for Battery Elimination Circuit. Some BECs are programmable so if lets say the input voltage is 12v the BEC can be programmed to reduce the voltage anywhere from 5-9v as an example. You would use a BEC for the flight controller if it didn't have its own regulator. Of course no BEC is required if the component is capable of taking the voltage straight from the main batteries.
 

Nov8er

Member
Voltage is relatively simple in principle.

That helped me understand things a little better. So the flight controller already has a regulator that can withstand a maximum voltage from the battery and decrease that voltage? Also, would most of the voltage bypass the flight controller, leave some voltage for the receiver, and run into the speed controllers?
 

Not necessarily. The FC and the Rx need 5v to operate. There are a few ways of achieving this.
One is via the ESC that has a Bec in it. If you use this method only one ESC needs to have a BEC so you buy 3 without one and one with one. Or do what I do and buy them all with a BEC and disconnect the red wire from the small plug on 3.
Once the ESC Is plugged in to the FC and the Rx is plugged into the FC then the power flows to both items.
If you choose to buy ESCs without a BEC then a separate BEC or Rx battery will do the same thing.
Some FC have a power module that will do the job. I have a Naza and APM FCs both have a power module but you can power each using an ESC with a BEC.
The choice is yours.
My question is if you are building a racer why do you want 15-20 flight time?
That is a long time to concentrate on a fast moving flying object.
I hope my words have been helpful
Regards
Crispy


Sent using fat fingers on the iPad thingy
 

PeteDee

Mr take no prisoners!
Multi purpose and racing are pretty much mutually exclusive, a racing quad would be around the 250 size and use 5 inch props, a multipurpose quad would be something around 450-500 size and use 9-10 inch props.
 

Nov8er

Member
Not necessarily. The FC and the Rx need 5v to operate.

Yes it very much helped me Crisp. I also thought on the question you asked me about the flight time. The reason why is that i heard racers fly somewhere around 5 min. To me 5 min would be like making a few laps and its dead out of energy, that is for a mini drone racer. I am making a frame 10"length and 4"width with atleast 6" motor arms. So a little bit bigger than a standard racer. I could live with 10-15 min but 5 is kind of short for what I'm trying to do. I think a 4s to 6s battery would fit my build. I also don't know if a 2300kv motor would run on 6s

*I'm really trying to make a bigger racer than the mini-drones.
*I don't really want it to go to fast but fast enough to race with.
 

You mist understand what the kv rating on the motors means.
For each volt applied the motor will spin at the stated rpm. Therefore a 1000kv motor with 1 volt applied will spin at 1000rpm. if you applied 5v to the same motor it will spin at 5000rpm and so on. These are theoretical values and due to looses and inefficiencies I am not sure how accurate they are.
If you used a 6s battery (nominally 20.4v (6x3.4v)) will spin those motors up at 46920rpm where as a 3s battery will spin them up at about 23500 rpm.
I use 3s and 4s batteries with 900kv motors for my quads.
Something to think about.
 

Nov8er

Member
You mist understand what the kv rating on the motors means.

Okay yea totally misunderstood. Thanks for telling me that Crisp. I had a difficult time understanding how the motors work with the batteries. Would a 2600mah 4s battery work decently for an 1000kv motor?
 

It is about doing calculations (or in my case trial and error). remember more cells in a battery then more weight therefore more thrust is needed and then you need to match the props to the motors. EG DJI motors say 3s use 10 inch props but on 4s use 8 inch.
What lots of people do is make a decision on parts and put up a shopping list on the forums and ask if anyone sees a problem. That is where lots of people have more experience than me. for reference my latest build is 500mm diagonal btween motors has DJI 980kv motors 10 inch props APM FC and hs a AUW (All up weight) of 1363g.
Regards
Crispy
 

Des

Member
Hi, following on from Nov8er (and thanks Nov8er for your questions - I had the same ones) Crispy your responses have helped a lot. Taking it a bit further, I am moving all my DJI gear (Naza M, PMU & iOSD-mini) to a new build - Tarot 680Pro using E-600's with a 22.2v 6S. I have conflicting advice from elsewhere about if I need to use a BEC or can power all this gear from the 6S. The donor quad I built originally uses 3S's. Sorry if this post is not in the right spot - I have just joined and jumped in here coz it was super in line with some of what I don't know.
thanks
Des
 

Gary Seven

Rocketman
Hi, following on from Nov8er (and thanks Nov8er for your questions - I had the same ones) Crispy your responses have helped a lot. Taking it a bit further, I am moving all my DJI gear (Naza M, PMU & iOSD-mini) to a new build - Tarot 680Pro using E-600's with a 22.2v 6S. I have conflicting advice from elsewhere about if I need to use a BEC or can power all this gear from the 6S. The donor quad I built originally uses 3S's. Sorry if this post is not in the right spot - I have just joined and jumped in here coz it was super in line with some of what I don't know.
thanks
Des
Hello @Des. You should definitely start a new thread. Better in the DJI General Discussions forum.
 



Des

Member
Hi. New thread started as suggested in DJI General Discussions. Lots of helpful advice from there already.
cheers
 

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