The Motor Driver¶

The L293 is the chip that actually drives the motor. This page explains what it does and why it exists.

Why a separate driver chip?¶

The Raspberry Pi's GPIO pins output only a tiny amount of current — enough to light an LED, but nowhere near enough to spin a motor. A motor needs far more current than the Pi can safely deliver.

The L293 acts as an amplifier and switch. It takes a small control signal from the Pi and uses power from the external power supply to drive the motor. Your Pi controls what happens; the L293 provides the power to make it happen.

How direction works¶

The L293 has two input pins for direction control: L293_INPUT1 and L293_INPUT2. The direction the motor spins depends on which pin is HIGH and which is LOW:

`INPUT1`	`INPUT2`	Result
`HIGH`	`LOW`	Motor spins one direction
`LOW`	`HIGH`	Motor spins the other direction
`HIGH`	`HIGH`	Motor brakes (both inputs same = no differential)
`LOW`	`LOW`	Motor brakes

The two pins must always be set to opposite values to make the motor spin. Think of it like a seesaw — one side goes up while the other goes down.

Try it

If the motor is spinning in the wrong direction, what is the smallest change you could make to the two digitalWrite() calls to reverse it?

How speed works¶

The L293_ENABLE pin is connected to a PWM output on the Pi. Writing a value from 0 to PWM_MAXVAL (1024) to this pin controls how much power the L293 delivers to the motor:

0 → motor off
1024 → full speed
values in between → proportional speed

See What is PWM? for how PWM works.

Summary¶

Pin	Controls	Function
`L293_ENABLE`	Speed	PWM value 0–1024
`L293_INPUT1`	Direction	Must be opposite of INPUT2
`L293_INPUT2`	Direction	Must be opposite of INPUT1