Can't switch N channel mosfet

Hello Guys,

I'm new to Arduino.

I'm working on a small project.
I need to turn on/off a power supply with my Arduino.

This is how it should work. If I pull the PS_ON to ground on the power supply it turns on but I have to keep PS_ON pulled down.

This is how I'm trying to make a switch with the Arduino and an N channel mosfet.

I've 5V going to the N channel Mosfet which I can turn on and off with my arduino.

The 5V goes to Gate. Source goes to ground. and Drain goes to PS_ON.
If I apply 5V to Gate the power supply turns on. However if I remove 5V from Gate the power supply is still on. For some reason the mosfet is not turning off. Why? What am I doing wrong?

Thank you.

Try putting a 10k resistor from the gate to ground.

I forgot to say that. If I have 5V applied to Gate it still not turning on until I short Drain to Source for a sec.

What part number is the mosfet?

Do you have the Arduino ground connected to the power supply ground and mosfet source?

hazardus:
If I apply 5V to Gate the power supply turns on. However if I remove 5V from Gate the power supply is still on. For some reason the mosfet is not turning off. Why? What am I doing wrong?

Thank you.

If you left the gate floating, it's going to float... MOSFET gates are insulated by a thin layer of silicon dioxide
so if you don' connect to them they act like the plate of a capacitor and hold charge till it leaks away somewhere.

Hi,

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Can you post a picture of your project so we can see your component layout.

Tom... :slight_smile:

As someone said in a previous post, i think you have not connected a ground to your arduino. Please look at this diagram, note that there is a motor and diode attached to Drain which in your case would be the 24 pin green cable and ground on the Source, you need a 10k resistor connecting the arduino ground cable to the arduino signal cable, plus a 220 resistor inline with the arduino signal cable. I’m sure you can read the diagram just fine.

MosMot1.png

Recommended practice is that in Kawasaki's diagram, the 10k should be on the other side of the 220, ie on the Arduino pin not the mosfet's gate.

kenwood120s:
Recommended practice is that in Kawasaki's diagram, the 10k should be on the other side of the 220, ie on the Arduino pin not the mosfet's gate.

It makes no practical difference as the gate drive voltage applied should be about twice the plateau
voltage anyway, so a percent or two change is immaterial unless the circuit is very bad in the first place.

Like this here, right here?
MosMot3.png

Yup, but the diode's only needed for inductive loads.