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I am trying to control my LED-strip with N-channel MOSFETs. The problem is it won't turn off after removing the current from the hate. More details below.

I bought these MOSFETs, and am currently using the Raspberry Pi 4 Model B with 4GB of RAM.

I wired everything as shown below according to this tutorial:

According to this tutorial https://www.youtube.com/watch?v=96uqxLQ_VFo&list=PL-xcHmoN4XSEhmKzXdra1Z5BuMtCddDaq&index=2&ab_channel=BasementMaker

For testing purposes, I used the 5V pin and only one MOSFET and tried it with only one LED.

The LED was off than I wired the 5V to the gate and the LED turned on.

The problem was that disconnecting this wire again didn't turn off the light. When I tried it with the same MOSFET again the light would be turned on from the beginning without anything connected to the gate.

Putting a resistor in-between didn't work either.

I'm trying to do the same thing but using the ESP32.

I hope that wasn't too confusing.

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  • \$\begingroup\$ Product description says BUZ11, but "Manufacturer reference:" is IRLZ44N. What is the actual part number of these FETs? \$\endgroup\$ Feb 6, 2022 at 20:03
  • \$\begingroup\$ One of the FETs does not have its gate connected. \$\endgroup\$
    – StarCat
    Feb 7, 2022 at 7:01

2 Answers 2

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You have to add a pull-down resistors in parallel from the gate of each MOSFET to a ground. Around 10K ohms will be fine for your application.

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Mosfets have voltage driven high impedance input that have some capacitance. If you charge up the FET gate to 5V, disconnecting a wire won't turn off the FET, as the accumulated charge can't discharge by itself. Except very slowly due to leakage.

Now if it were a BJT, it would stop conducting as it has a current driven base input.

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