What MOSFET to use with 8520 motor

Hello

I am building a small drone.

I got 4 8520 motors and 4 MOSFET to control them. I use arduino nano to control motors via PWM pins

I noticed that motor spins much slower for some of the transistors.
Is it a bad transistor?
Is there any way to test transistor?
Is it a good transistor for such project?

Here is the motor - https://www.amazon.com/gp/product/B01M7TX4KS/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

Here is the transistor - https://www.amazon.com/gp/product/B01GNORMWA/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

Here is the circuit

That Fritzy picture is almost useless without values. And links to the actual modules used.

I assume you're NOT using a 9volt smoke alarm battery, because that wouldn't be able to power the setup.
Calculated stall current for those four motors combined is >30Amp.
That makes those pictured motor buck converters useless for that task.

I assume you know that V-in on a Nano needs at least 6volt (7-12 in the datasheet).
5volt on V-in would reduce the mosfet gate drive voltage.
Leo..

Edit:
Cross-posting is also bad.
https://forum.arduino.cc/index.php?topic=543150.0

How did you calculate the stall current? I can't see any rating for it or winding resistance.

The issue sounds like you are trying to drive MOSFETs designed for a minimum of 5V gate
drive from 3.7V.

You need MOSFETs rated for 3.3V operation, which typically are not TO220 package, but
surface mount. You are using free-wheel diodes too I hope - essential...

Banggood lists a resistance of 0.4ohm and >=10A stall for Racestar 8520 drone motors.
Amazon mentions 100mA.
Leo..

I can believe quite high stall currents - I believe some of these motors are rated at 1 to 2A running, the 0.1A
is probably spurious.

Thank you guys for comments.

First of all: Cross-posting is necessary as problem exists and people who asked me to provide more details in another thread don't follow up or don't want to follow up.

The issue sounds like you are trying to drive MOSFETs designed for a minimum of 5V gate
drive from 3.7V.

I don't think this is true. I use Arduino PWM pin to control gate. 3.7V is for motor. PWM pin should generate 5V.

This is the link from LHI website - Loading...
It says current 0.1A.

Wawa, could you post link that specifics

I wasn't aware about that

I assume you know that V-in on a Nano needs at least 6volt (7-12 in the datasheet).
5volt on V-in would reduce the mosfet gate drive voltage.

But, the same behavior happens when I connect Nano to USB port. I assume USB will give enough voltage. What will happen when both Vin and USB port are used. What source will be selected?

afedorov:
This is the link from LHI website - Loading...
It says current 0.1A.

It also says the motor is 7mm x 20mm. But it isn't. 8520 means 8.5mm x 20mm. So definitely not a reliable source. I've used a few of those motors and 1.5-2A is more likely though 45mm is a rather small prop.

Steve

So If I can't trust documentation, how can I figure out the max current I can push through the motor?

You can't "push" current through a motor. The motor will draw whatever current it needs depending on the load on it (in this case the size of the propeller if you're using those motors for their intended purpose).

The current draw is not easy to calculate unless you have all the motor parameters. But you can always measure it if you have a DMM.

Steve

So if I have a battery of 600mA, It means that 4 motors can't get more than that, so they approximately will take ~100mA and leave something for Nano. Should I try with "better" battery to see if it will take more?

No, you're reading that wrong. Batteries specifications normally give the capacity in mAh. That's not the same as current, measured in mA. A good 600mAh capacity battery may be able to deliver a current of 15A or even more.

So exactly what battery are you intending to use?

Steve

Those drone motors are made for a single LiPo battery (3.7volt).
The motors alone (without fet) seem to have a resistance of 0.4ohm (Bang good site).
Leo..

I was planning to start with the batteries like this - https://www.amazon.com/EBL-Battery-Charger-Rechargeable-Batteries/dp/B00HV4KFSA/ref=sr_1_4?ie=UTF8&qid=1526340938&sr=8-4&keywords=battery+9v+rechargeable

BL 840 9V Battery 600mAh Li-ion Rechargeable.

I wanted to make it spin first before I get into LiPo batteries. It spins now but doesn't go into the air. Should I try LiPo now?

The problem I want to solve particularly in this thread is the different behavior of the motor with different transistor. All transistors are of the same type but motor spins differently

If the resistance of the motor is 0.4ohm does it mean that it can handle around 10A (3.7/0.4)?

You might not get the drone in the air with 9volt batteries and a large (heavy) circuit board.
Weight is important...

A buck converter is not 100% efficient, and the ones you use can't supply 30Amp.
Get rid of the buck converters, and the 9volt batteries, and use a 3.7volt drone battery for the motors directly.

A tiny (weight) 5volt boost converter powered from the same battery could be used for the Arduino and sensors.
Must use 5volt logic for those TO-220 mosfets.
Leo..

Could you recommend boost converter? I have this one https://www.amazon.com/gp/product/B06XHJCHX6/ref=oh_aui_search_detailpage?ie=UTF8&psc=1. Is it ok?

Also, when you say "Must use 5volt logic for those TO-220 mosfets", what do you mean? I use Arduino Nano's PWM outputs to control motor - as I understand it should have 5 volt output.

I also tried to run motors with other transistors. Apparently, first batch was bad, because I am able to get faster speed with new transistors.

The issue I face now is if I run motors with propellers attached, the application dies as I reached 10-15% of motor power( arduino PWM value is around 20-30). If I detach propellers I can get higher speed.

Can it be related to the battery I use? Something like, propellers causes higher power consumption that affects controller?

For a small drone, I would pick someting 1/4 the size (weight).
Something like this. Pololu 5V Step-Up Voltage Regulator U1V10F5
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..

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

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?

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..

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.

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