The traditional way to open and close the throttle was with a steel cable,
like this one right here.
Today, just about every car uses electric motors, electronics and wires to control the throttle. This is known as a “drive by wire” system or electronic throttle control (ETC).
To show you how this works in detail, we have made a simple “drive by wire system” Let’s check it out.
and here it is….
Now, I know it doesn’t look like much, but it functions the exact same way.
Let me explain the parts. This is a position sensor that is very similar to the one in the accelerator pedal. Turning it changes the voltage that is read by our ECU, which is a $13 micro controller.
We have programmed it to read the dial’s position, do some calculations
and then control how much power is sent to the motor in the throttle body.
The more the dial is turned, the more power is sent to the motor, which
opens the throttle plate.
BUT our micro controller ECU, can’t handle very much much power,
so we have it control a high power electronic switch, called a MOSFET.
and that controls how much power is sent to the motor.
Let’s have a closer look at just the motor.
The more power I apply, the faster it turns.
just like any electric motor in a remote control toy.
OK, now that we understand the parts of a drive by wire system
let’s look at the signals running in the wires.
Let’s have a closer look at the signal being sent to the motor.
This line is 0 volts, and this one is 12 volts.
Let’s turn the dial and see what happens.
We can see the output switches very quickly from 0 to 12 volts.
This is called a square ware, because um it has squares in it.
Anyways, if I turn up the dial, we can see the squares get wider.
The wider the squares, the more power is being sent to the motor,
since it is spending more time at 12 volts then off at 0 volts.
This is known as “pulse width modulation” and is used to control how much
power is sent to many different types of devices, like lights and motors.
Some think that drive by wire systems are slow and don’t respond fast.
However, they can be programmed to be very quick!
Just for fun I programmed it to be a “wide open throttle” button.
Let see how quick it is…
I hope you have a better understanding of how Drive by wire systems work.
We used a $13 Arduino Uno clone from amazon to read the voltage output of a position sensor which then sent a pulse width modulated signal to the electric motor in the throttle body.
The throttle body used in the episode is from an Infiniti G37, and is typical of most throttle bodies.
