Raspberry pi 3 with mosfet for 18v led

Question

I need your help because I do not know much about electromagnetics.

I use Arduino UNO for control blinking LED(Cree CXA 1512 18v) fast(< 100KHz). Until now, i have used following circuit.

^{simulate this circuit – Schematic created using CircuitLab}

My project is changing micro controller Uno to RPI 3. However, If i just change it, circuit doesn't work. I think that the reason is RPi's GPIO output voltage is 3.3v. (And Arduino Uno is 5v, right?)

1. Why this circuit doesn't work?
2. So what should I do to make the circuit work with the RPI?
3. I think i should change the MOSFET, do you have any product to recommend?
4. And there are any other problems? (such as safety? I always afraid about electric shock....)

Answer 1

Yes, the reason is RPi's GPIO output voltage is 3.3v, and your mosfet is not designed for 3.3V logic level driving.

Replace the mosfet with one that has a vgs on of under 3.3V, replace it with a NPN transistor so you can use current instead of voltage to turn it on, or use a mosfet driver cricuit, like a 2n3904 npn to turn on and off the mosfet from your RPi with a higher voltage.

Answer 2

You can use NTD5865 for switching with Pi. It works with 3.3V drive voltage.