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Transistor

In Fab Labs we use MOSFETs to turn things on and off. There are two types, depending on where in the circuit you want to place the MOSFET.

  • You put a P-channel MOSFET between the load and the voltage source (P for Positive).
  • You put an N-channel MOSFET between the load and ground (N for Negative).

N-Channel MOSFET breakout board

Here's the simplest possible board to try out a transistor. You can use it to turn a 5V load like a small DC motor on and off.

We're using the smaller type of N-Channel MOSFET in the Fab Lab Inventory, which has a SOT-23-3 footprint and looks exactly like a regulator and a Hall effect sensor. Don't get these components mixed up!

Note

If you have an older type of N-Channel MOSFET with a SOT-23-3 footprint in your inventory, you can use it, just check the datasheet to make sure that the pinout is like this:

N-MOSFET pinout

Schematic

MOSFET Schematic

PCB

Notice that the 5V wire goes straight to the load (in this case, the DC motor) and the N-Channel MOSFET (the negative type of MOSFET) is connected to signal and ground.

MOSFET PCB

PNGs for mods

Traces (1000 DPI): Traces

Interior (1000 DPI): Interior

MicroPython code

Connect the signal pin on the board to pin 0 on the Raspberry Pi Pico. Connect the 5V pin to the VBUS pin and GND to GND.

You can also use the Xiao RP2040, see the pinout from Adrián Torres. Use pins D0, 5V and GND.

from machine import Pin
motor = machine.Pin(0, machine.Pin.OUT)

motor.toggle()