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Topic: What MOSFET to use with 8520 motor (Read 923 times) previous topic - next topic

Wawa

#15
May 15, 2018, 06:39 am Last Edit: May 15, 2018, 06:41 am by Wawa
For a small drone, I would pick someting 1/4 the size (weight).
Something like this. https://www.pololu.com/product/2564
And maybe a 5volt ProMini instead of a Nano (heavy USB socket).
And smd mosfets instead of the heavier TO-220 package.
But I never actually build a drone.
Maybe you should ask these things on a drone forum.
Leo..

slipstick

That battery is useless for high power requirements like flight. But you're lucky because 9V is also far too high for those motors but the battery is so feeble that it probably hasn't destroyed the motors yet.

You need a 3.7V 1S lipo. Get one from somewhere that deals with drones/aircraft and has a C-rating of at least 20. Something like https://hobbyking.com/en_us/turnigy-nano-tech-600mah-25c-lipo-battery-walkera.html

Steve

afedorov

#17
May 17, 2018, 06:25 pm Last Edit: May 17, 2018, 06:26 pm by afedorov
I got all the recommended components - lipo battery and boost converter.
I take 3.7V straight to motors and use converter to get 5V that I attached to 5V pin.


 It looks like that motors and transistors work fine with new supply source. But I see the controller is going to a weird state when I start increasing throttle. It becomes unresponsive and sometimes restarts.

It works fine when I detach motors.
I use 433MHz transceiver/receiver to control the drone remotely. I thought that unresponsiveness may come from noise that maybe produced from motors, although it is not clear how as everything is separated with MOSFET.
But even this doesn't explain restarts.

I also see garbled symbols in serial port when drone goes to "nirvana".

Can it be again related to issues with controller power supply?


Wawa

A super regen 433Mhz AM/OOK receiver is ofcourse useless with motor noise near.
Not sure what works best with drones, but I suspect some sort of 2.4Ghz nrf24L01 would be preferred.
Leo..

slipstick

I got all the recommended components - lipo battery and boost converter.
I take 3.7V straight to motors and use converter to get 5V that I attached to 5V pin.


 It looks like that motors and transistors work fine with new supply source. But I see the controller is going to a weird state when I start increasing throttle. It becomes unresponsive and sometimes restarts.
Exactly what lipo battery did you get? And have you fully charged it? Increasing the throttle takes more power from the battery. Becoming unresponsive and resetting are classic symptoms of a battery not able to provide enough power.

Steve

afedorov

I use this batteries - https://www.amazon.com/gp/product/B074J74S2K/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1

I will try to charge them longer and see how it behaves.

Is there a way on Arduino side to detect low power and stop motors for example?

Wawa

Is the battery<>fet<>motor wiring able to handle the motor current.
Thin hookup wire is ofcourse not ok.
Leo..

slipstick

I use this batteries - https://www.amazon.com/gp/product/B074J74S2K/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1

I will try to charge them longer and see how it behaves.
Those batteries should be o.k. and almost any wiring should be o.k. for the current you're using.

If you have a multimeter measure the battery voltage. It should be close to 4.2V when charged. You do need to use a proper lipo charger and it will stop when the battery is full.

Steve

afedorov

Multimeter shows 4.15V.  The charger that goes with batteries "guarantees" no over charge.

I am still seeing discrepancy in motors' behavior. Two motors spin much faster. I basically can lift only one side of the drone from ground. And drone often becomes unresponsive If I am trying to control it via 433MHz tr/rc.

Is there a programatic way to detect that controller doesn't get enough power and shut it down or indicate somehow? It doesn't look like a bug in the code as it works fine when motors are off and I see communication happens in between drone and radio controller.
 
How does it work on factory-made drones? They don't go to weird state when battery is low.

slipstick

It sounds like there may be problems with your code but we've never seen that so can't really help with it. And of course you can't know how well it works with no motors. Without the motors it doesn't do anything useful at all.

But as already said most drones use 2.4GHz RC systems and one reason is that these are a lot less likely to be disturbed by motor noise than a basic 433Mhz radio setup.

Steve

afedorov

Thank you for help,

I will got new 2.4GHz chips and try them. I also will simplify the code and circuit  to do tests with motors and battery.

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