IRF520N Mosfet and 6-9 volt dc motor

Is there something about this mosfet that makes the motor start off slowly?

Im using PWM pin 9 on an Arduino Mega and using a push button.
The PWM pin 9 is set to HIGH when the button is pressed.
But the motor seems to start off with a LOW setting, then ramps up gradually.

Am I using the wrong Mosfet? The IRF520N came out of the MKR IOT BUNDLE KIT.

There are two of them, and I tried them both with the same results.

If I am using an undesirable mosfet, then what would you suggest in its place?

Thanks,
-rb

Nobody answer a question that contains no information.
A. Motor specificaions link
B. Power supply Specificaions (voltage/current)
C. Motor LOAD specifications
D. schematic

FYI, all motors are subjec to startup inrush current and inertial resistance . There is no motor that
can go from dead stop to maximum rpm instantaneously. And then there's the crappy
mosfet.

Use analog inputs to plot output vs input.
Use voltage dividers where needed to limit
analog input voltage to < 5V.

If the motor starts up very slowly then it is perhaps more likely to be a power problem. How are you powering the motor?

Having said that the IRF520N is not a good MOSFET to use with Arduinos because it is not a logic level device so may not be fully switched on with only 5V. There are many better. The (L for logic level) IRL520 or even the old IRL540 work well depending on how much current you need to switch.

Steve

Am I using the wrong Mosfet?

Yes, the IRF520 requires 10V signals to fully switch on. Use a logic level MOSFET instead, like this one.

It is really, really stupid and disrespectful of kit manufacturers to include the IRF520, but several do it anyway.

jremington:
Yes, the IRF520 requires 10V signals to fully switch on. Use a logic level MOSFET instead, like this one.

It is really, really stupid and disrespectful of kit manufacturers to include the IRF520, but several do it anyway.

Funny you should say that, because the mosfets came with the MKR1000 Bundle from the Adruino.cc store.
Thank you for your input. :wink:

slipstick:
If the motor starts up very slowly then it is perhaps more likely to be a power problem. How are you powering the motor?

Having said that the IRF520N is not a good MOSFET to use with Arduinos because it is not a logic level device so may not be fully switched on with only 5V. There are many better. The (L for logic level) IRL520 or even the old IRL540 work well depending on how much current you need to switch.

Steve

Thank you Steve. I'm using a 9 volt battery to power the motor.
I got the motor, and the mosfets from the MKR1000 bundle sold in the arduino.cc store.
I cannot yet understand the science from the data sheet on the IRF520N
And there were no specs given for the motor other than "small dc motor 6-9v"

I will try the IRL, thank you.

because the mosfets came with the MKR1000 Bundle from the Adruino.cc store

Complain to the Arduino store. Forum members are volunteers, and have no input to or control over the bad decisions the store owners make.

I cannot yet understand the science from the data sheet on the IRF520N

What in the data sheet is giving you difficulty? Vgs must be around 10V to turn the IRF520 fully on. The Arduino cannot do that.

From the IRF520 data sheet:
IRF520.png

IRF520.png

Most (not all ) mosfets use an external PSU to the motor and simply take on the task of a SWITCH.

Nick has some great tutorials for these and other aspects of Arduino.
You will find his name all over the place for a trusted source of ARduino information.

Bob.

Edit.

Seeing this listed with a few different VGS with some listed as 4.2 v max.
Not sure why there are so many seemingly different measurements for this ?
However an Arduino is more than capable of the 4.2 so maybe there are variants ?

Ouch. Some of you guys are brutal.

Thanks for the input where it was valid.

Most of the advice given by forum members is valid.

You are welcome!

Seeing this listed with a few different VGS with some listed as 4.2 v max.
Not sure why there are so many seemingly different measurements for this ?

You are probably looking at this specification for Vgs(th), which tells you when the MOSFET just starts to turn on:

Gate-Source Threshold Voltage VGS(th) VDS = VGS, ID = 250 μA 2.0 - 4.0 V

For the IRF520, Vgs (max) is +/- 20 V.

FYI

rjbuckley:
Thank you Steve. I'm using a 9 volt battery to power the motor.

Despite all the talk about MOSFETs that isn't your major problem. The one change you NEED to make, if that 9V battery is a little rectangular smoke detector type, is to use 6 x AA alkaline cells instead of it. The difference is likely to be impressive even if you stick with the (not so good) IRF520 MOSFET.

Steve