Controlling Coreless motor using mosfet

Hello, Im new to using the forum so I apologize for any mistakes. Im trying to control a 3.7v 10mA coreless motor using arduino, I`m using a 2n7000 mosfet, 2 18650 batteries ( adding to 8 volts).
I read that the coreless motor pwm frequency is more than 20KHz so I edited the code as such.

The setup is simple :
the gate is to pin 9
the source is to ground
the drain is to terminal of the motor
the other terminal is attached to the positive of the 8 volts

Here is the problem, at pwm 255 , the motor is reading 1.43 volts, and the mosfet heats up a bit.
I don`t understad what is wrong. TIA

#define motor 9   

void setup() {
  pinMode(motor, OUTPUT);

  // 32 KHz
  TCCR1A = (1 << COM1A1) | (1 << WGM11); 
  TCCR1B = (1 << WGM12) | (1 << WGM13) | (1 << CS10); 
  OCR1A = 500; 
}

void loop() {
  analogWrite(motor, 255); 
}

10mA?
Must be the size of half a grain of rice then...

Common coreless motors used for small drones can draw up to 8Amp@4volt.
Leo..

What a coincidence!!
Even I am trying to make a drone with Coreless motors or micromotors.

  • Model: 716 coreless motor.
  • Shaft Diameter: 0.8mm.
  • Rod Length: 8.2 mm.
  • Motor Diameter: 7 mm.
  • Motor Length: 16.5mm.
  • Wire Connection (10cm): Red (Positive Pole), Blue (Negative Pole)
  • Voltage Range: 1V to 3.7V.
  • Current: 0.01 A.
  • Speed: 50000 RPM. (at 3.7V)

I am really stuck here, when I connect a dc geared motor (the yellow one) it works properly so I don`t get the problem.

My coreless motors work on 3.7v. I think the mosfet is trying to reduce voltage by turning it into heat.

which mosfet are you using?

You must have a different definition of small.

Using conservative calculations

A 250 mAH cell can

run 4 14x7 brushless cordless motors

for a 5 minutes flight

which woukd be ~4 amperes continuous current

or about 1 ampere per motor.

I would say 8 Amps at some point isn't impossible, 2 amps per motor.

I'm more curious about

Since motors don't have a "pwm frequency" other than someone's recommendation. I want to read that for myself to see who said and what else.

a7

Why are you running a 3.7V motor on 7.4V?
Could that be the problem?

1 Like

She said N type but she didn't say the no.
Example- Irz44n

Tell it not to.

That is to say, that's not how MOSFETs in a circuit like this work. They do no thinking or trying, they are supposed to turn on and off.

Draw a proper schematic and say what part that is. Are you sure it is a MOSFET, and that you are meeting its gate voltage for getting a low resistance on state?

a7

Coreless motors should be used with High Frequency Multifunction Decoders . Some manufacturers recommend a PWM frequency greater than 20kHz. This increases the motor's impedance when driven by a multifunction decoder's motor drive circuits. Not all manufacturers will publish the PWM frequency in their literature.

Coreless Motor - DCCWiki.

1 Like

I am using Irfz44n

I said 2n7000 in the post

Im using an arduino uno and a servo besides the motor so I have to power them up. For clarification, Im not using the srvo right now I`m just testing the brushless motor

OK, no need to be rude

I am really sorry, this wasn`t my intention. I only just meant to clarify. Sorry again.

If you are in India then you can buy from this link

https://www.amazon.in/Electron-Coreless-Magnetic-Robotic-Helicopter/dp/B0CRWRFH3K?source=ps-sl-shoppingads-lpcontext&ref_=fplfs&psc=1&smid=A3C7Z4RVM9A3G1

It's okay

Fine but what voltage are you applying to the motor 3.7V or 7.4V?