Electrical – Hot Mosfet IRL540N with Gate 5v and Source 12v-260 mA


I've connected the + of a 12v powersupply to a 12v LED-spot.
The – of the LED-spot is connected to the source of a IRL540N mosfet.
The drain is connect to the – of the 12v power supply and the ground of a arduino uno.
The gate of the mosfet is connected to the 5v regulated output of the arduino.

If I connect the LED-spot directly to the 12v power supply, I measure 260mA.

The mosfet is getting very hot in notime. I've bought this mosfet as it should handle a gate voltage of 5v better. As I read the documentation of the mosfet the resistance of the IRL540N should be 0.05.

In this setup, if I disconnect the LED spot and measure the resistance between source and drain I measure 0.5 Ohm.

Do I have a problem in my setup, or should I use a different mosfet? I've read many posts on this subject on this website already but my background knowledge is too limited to pinpoint the problem.

My question is: Am I using the correct mosfet? I don't understand why the mosfet is getting very hot

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Best Answer

You seem to have the source and drain terminals swapped over from your description (But not from the picture of the breadboard), the source should go to power supply negative, the drain the negative lead from the lamp.

Measure the actual gate voltage (Between gate and source), could it be 3.3V and not 5V? That mosfet will be unpleasantly resistive with only 3.3V on the gate.

Are you by any chance trying PWM dimming? That mosfet has a huge miller capacitance (All big vertical power fets do), and your gate stopper might be slowing the rise time so much as to cause the thing to spend significant time in the linear region if run above a few kHz.