Hey guys, short time reader first time poster.

Quick preface, I have a tendency to attempt to understand things as well as my amateur mind allows, as a result I find myself falling into tangent loops quite often.  I had no idea how complex a system is required to keep a multi rotor craft in the air.  That being said, onto my question...

I think I've got a decent grasp on the basic interactions between the various components of a multi rotor craft based on my last week of reading and stitching various forum posts and articles together.  I'd greatly appreciate confirmation on what I got right and input on the big deal stuff I'm missing.

As I understand it, the path a command follows is from Tx to Rx, Rx to FC, FC to ESC, and ESC to Motor.

I haven't done much reading on Tx to Rx to FC communication and encoding, so I'll leave that for another post, and just assume that it works becasue it works

The FC and ESC each have their respective Firmware

 - FC have Cleanflight, KISS and so on

 - ESC have SimonK, BLHeli, KISS and so on

The ESC also have a protocol which as far as I can tell determines the PWM pulse length, refresh rate and delay, and PID loop timing

 - I'm fairly certain that which protocol you choose depends on the ESC firmware you choose and hardware limitations of the FC (ESC hardware?)

 - I'm incredibly sketchy on how PID loop timing is affected by PWM pulse length

 - I'm not sure where the PWM pulse originates, is it the FC that produces it and the ESC simply acts as a conduit, or does the ESC take inputs from the FC hardware (CPU, Gyroscopes and Accelerometers) and convert it into PWM output?

- Where does the PDB fit into this equation, does the FC tell the ESC how much current to request from the PDB?

Anyways, these are a few of the things that are perplexing me at the moment, I'm kind of an idiot with most everything, so any help is appreciated.

Thanks in advance and I hope to be around for a long time to come

- Where does the PDB fit into this equation, does the FC tell the ESC how much current to request from the PDB?

The PDB is just a connection joint for the ESCs to get power and most PDBs also got a 5V and 12V regulator for the FC, VTX, Camera ETC. Some PDBs got a current meter but that is just for telling the FC or OSD how much current is consumed so you can keep track. The FC doesn't care about it and just sends a speed command to the ESC (the PWM signal), which based on the signal, tells the motor how fast to spin (keep in mind that this is a very simplified explanation). The motors is then drawing as much current they need to try to keep the RPM the ESC's want it to have. If you have a prop that is too heavy for motor to run, you will notice when you fly that the current draw goes up, but not necessarily the motor speed. and some of the extra current consumed goes to heat in the motors, which you can feel on the motor temperature when you land.

The PID loop timing is done by the FC and not by the ESC's.
The ESC's just convert the speed command in a switching patern for the motor wires to let the motors spin. (very basicly)

Here you can find some information regarding the PID looptime and the different PWM signals (PWM, oneshot, multishot, etc):

https://oscarliang.com/best-looptime-flight-controller/

About PDB - I revisited my post about a week ago... still got to add more and update the post but it should answer some of your questions already:
https://oscarliang.com/power-distributio...able-wire/

PDB is just a electrical connection between battery and ESC, think of it as just a wire that's why you can also replace PDB with just wire harness...

Thanks for the quick responses everyone, that loop time link is exactly what I was looking for oyvinla, gives me a lot of stuff to read. I was most interested to read about the interaction between various timings, PID, ESC Protocols Refresh, and FC sensors.

And thanks for the PDB link Oscar, I hadn't thought about a wire harness, not sure I'd go that route as it seems to eliminate the telemetry available with a PDB... Correct me if I'm wrong.

(05-Dec-2016, 06:08 PM)TeamPlayerGuy Wrote: And thanks for the PDB link Oscar, I hadn't thought about a wire harness, not sure I'd go that route as it seems to eliminate the telemetry available with a PDB... Correct me if I'm wrong.

Yes wire harness is really old school, I personally wouldn't ignore PDB due to the rich features it provides nowadays.

here Oscar i would take other stance...
previously you had to have everything connected to 5v... and simple pololu sometimes wasnt enough...
"nowadays" most of components can be powered directly from battery... + cap (to kill noise)
there is a chance that in 2-3 months we will see more "harness" builds and PDB will be considered a nice "clean" build

(05-Dec-2016, 09:40 PM)Grisha0 Wrote: here Oscar i would take other stance...
previously you had to have everything connected to 5v... and simple pololu sometimes wasnt enough...
"nowadays" most of components can be powered directly from battery... + cap (to kill noise)
there is a chance that in 2-3 months we will see more "harness" builds and PDB will be considered a nice "clean" build

Or FC integrated into PDB and completely eliminate the need for that medium!   (or the other way round if you are a FC supporter lol)

(05-Dec-2016, 09:40 PM)Grisha0 Wrote: here Oscar i would take other stance...
previously you had to have everything connected to 5v... and simple pololu sometimes wasnt enough...
"nowadays" most of components can be powered directly from battery... + cap (to kill noise)
there is a chance that in 2-3 months we will see more "harness" builds and PDB will be considered a nice "clean" build

Hey Grisha0, welcome to the conversation , could you please explain the basics of how noise will affect the operation of a quad?  I've seen the term thrown around quite a bit, especially in relation to PDB/FC/Rx all in one boards.  Are we talking about video static, interruptions in the control signals, both?

Also, if you were to run power directly from the battery, as many modern FPV components can handle the higher voltage, you mentioned a cap.  Are you creating a simple circuit with a soldered capacitor interrupting the current?

Don't let me take too much of your time, I really need to read up on the basics of electrical engineering some day soon.  I figure that would give me a good footing when it comes to the various interactions between components.  I'm more interested in your anecdotal experiences with what you find works and what you find causes electrical noise.

1. im no expert - i only try different stuff and spend too much time on it
2. im no expert in electronics nor soldering - basics only
3. i try to have open head (unless it is Konrad with his hints or ideas (after two months i say "why didn't you said that earlier"))

why noise is bad ? despite video problems it can fry your equipement... so it is good not to have it.

key learning low esr cap... to kill the noise... how it works:


ofcourse there are dedicated lc filters and caps and pdbs and whatever...
if it is simple and goes over 80% of the way... it is a good solution to start with.

(06-Dec-2016, 12:37 AM)Grisha0 Wrote: key learning low esr cap... to kill the noise... how it works:


ofcourse there are dedicated lc filters and caps and pdbs and whatever...
if it is simple and goes over 80% of the way... it is a good solution to start with.

Very cool video, did some reading on oscilloscopes, looks like I've got another piece of equipment that I "need to have."

Correct me if I'm wrong, noise is excess current that sneaks past voltage regulators when a device like a motor draws a lot of current?  This leads to visible electric noise in the video feed and "invisible" noise that can overload the capacitors on the lower voltage 5v and 12v components (Rx Tx FC...)

Noise is actually voltage spikes that mostly comes from the motors/escs and since we are using escs with regenerative braking, we will often see a lot of noise. If you study the video, you will see that the oscilloscope is measuring about 30volts at the top of the spikes

(06-Dec-2016, 09:53 PM)TeamPlayerGuy Wrote: Very cool video, did some reading on oscilloscopes, looks like I've got another piece of equipment that I "need to have."

Correct me if I'm wrong, noise is excess current that sneaks past voltage regulators when a device like a motor draws a lot of current?  This leads to visible electric noise in the video feed and "invisible" noise that can overload the capacitors on the lower voltage 5v and 12v components (Rx Tx FC...)

Electrical noise can also upset the gyro for example, or shift esc signal levels which can lead to a variety of problems.

(06-Dec-2016, 11:20 PM)oyvinla Wrote: Noise is actually voltage spikes that mostly comes from the motors/escs and since we are using escs with regenerative braking, we will often see a lot of noise. If you study the video, you will see that the oscilloscope is measuring about 30volts at the top of the spikes

(07-Dec-2016, 07:37 PM)fftunes Wrote: Electrical noise can also upset the gyro for example, or shift esc signal levels which can lead to a variety of problems.

You guys have given me lots more stuff to read about, I'm going to take a break from posting replies and do some reading, but I'll be back one day soon to ask loads more questions. Thanks for the quick replies and words of help.