How to control a 12 volts DC motor (or solenoid) from your Raspberry Pi

Introduction

Raspberry Pi GPIO pins work at 3.3 volts and the current you can draw from them is quite limited for many applications (16 mA – 50 mA).

An external power source and a power interface are required to control a 12 volts DC motor (or solenoid) from a Raspberry Pi GPIO pin.

Materials

• N-Channel MOSFET (FQP30N06L/RFP30N06LE) x 1
• 10 kΩ resistor x 1
• 1N4001 rectifier diode x 1

Schematic diagram

Wiring diagram

Components explanation

The power interface between our Raspberry Pi signal pin and the 12 volts DC actuator we’d like to control is a MOSFET (metal–oxide–semiconductor field-effect transistor).

The 10 kΩ resistor is used as a pull down resistor for the MOSFET to have a well defined gate input level at any time.

FInally, the rectifier diode 1N4001 is for kickback protection (should be placed across solenoids, relays & DC motors to safely discharge the spikes generated by the coils and avoid damaging the Raspberry Pi signal pin)

Python test code

#! /usr/bin/python

import sys
import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)
CTRL_PIN = 4
GPIO.setup(CTRL_PIN, GPIO.OUT)

print "SOLENOID CTRL Test (CTRL+C to exit)"
time.sleep(2)
print "Ready"

try:
  while True:
    print "On"
    GPIO.output(CTRL_PIN, True)
    time.sleep(1)
    print "Off"
    GPIO.output(CTRL_PIN, False)
    time.sleep(1)
except KeyboardInterrupt:
  print 'Quit'
  GPIO.cleanup()
except:
  print 'Unexpected error: ', sys.exc_info()[0]

This python program will turn on/off your motor every second until you exit the program by pressing CTRL + C.

Note that the control GPIO pin is defined in the program as pin number 4 (see the wiring diagram above).