Arduino #10 - Ultrasonic HC-SR04 Range Sensor - Robotics Arduino Tutorial

those are going guys let here welcome to
the 10th are doing a tutorial in which
we're going to discuss ultrasonic
sensors and as you can see I have the HC
SRO for one of the most popular and
inexpensive sensors on the market right
now so first and foremost it is a 4 pin
device as you can see right here so you
have your voltage your ground your trig
and your echo pins so in essence what
you require to do with this sensor is
supply 5 volt and the ground and you're
going to be sending out a an ultrasonic
pulse and then reading back on the echo
pin - obviously determine the distance
and all that is explaining the data
sheet which will overview will also
discuss what kind of useful functions
you can have on the Arduino in order to
facilitate the reading for the sensor so
without any further delay let's get the
data shoot of the sensor you're going to
find a section which is called the
timing diagram which is going to explain
how to actually send and receive the
trigger as well as the echo signals so
as you can see the timing diagram is
shown below you only need to supply a
short 10 micro second pulse so that is
something that you need to keep in mind
so you're going to send a high pulse for
10 microseconds the input to start the
ranging so the module will send out an 8
cycle burst of ultrasound at 480
kilohertz and raise its echo so that's
not really important to you as this
function is on the module itself
the echo is a distance object is pulse
width and the range in proportion
so what this means is the return signal
is going to the length of the return
signal is going to be based on the
distance of the object that you're
seeing in front of the sensor so you can
calculate the range through the time
interval between sending trigger signal
and receive echo signal and that
essentially is the time in microseconds
divided by 58 which is just a scaling
factor that comes with the sensor and
that's going to give you your distance
and centimeters or if you want to divide
by 148 you will get it in which is
otherwise you can do a timing diagram
based on the as I said on the time of
the signal elf and as you can see we
suggest use over 60 mo second
measurement cycle so that means you
shouldn't be triggering the sensor over
60 milliseconds between the readings so
let's take a look at what Arduino
libraries are going to help us implement
these so the first function is fairly
self-explanatory and I believe used it
in a couple of preceding tutorials it is
the delay microseconds function which is
instead of millisecond sets your delay
in microseconds as the name suggests so
that's very important in order to time
the trigger signal the second function
that's going to be very important to us
is the pulse end function so quickly
going through the description it reads a
pulse either high or low on a pin so as
an example if you set it too high it's
going to wait for the pin to go too high
it's going to start a timer and then
it's going to end a timer one depende
transitions too low so this will return
the length of the pulse in microseconds
which is exactly what we need to use in
our calculation so it returns zero if
the pulse starts within a specified time
out so the syntax you can either specify
it with the time out or not you have to
specify the pin and the value either
high or
low so this is fairly simple as well
let's quickly go through an example so
on pin 7 we're going to look for a
duration and the way you set it up is
your PIN is going to be an input and
you're going to instruct a pulse n on
pin 7 high so that's going to wait until
the pin goes side time the transition
from that high to low and return the
duration in micro so this program is
going to incorporate several functions
which have just explained and from
previous tutorials so we're going to
define both of our trig and echo pins as
well as an LED pen in order to have a
visual display of the distance acquired
by the senses so the set in the setup
we're going to have an output for the
trig as well as the LED and an input for
the echo pin in our loop we're going to
make sure that the trigger pin is set
before we send any signal so chary glow
and a delay or seconds to we're going to
do a digital right high delay for 10
microseconds and then digital right low
so this is going to send a pulse to the
sensor in order to start outputting its
ultrasonic wave so this has been
described in the datasheet we are then
going to capture the returning pulse
through a pulse in a function so the
duration is going to equal to the pulse
in echo high so once again what this
does is it waits for the for the pin to
go high and then
timer starts and timer ends on low so
when the pin is low this is going to
stop timing and our distance based on
what is described in the datasheet is
going to equal the duration of the pulse
divided by 58 if you want a distance in
centimeters if you want it four inches
divided by 148 and this is a PWM output
or the LED so this is simply going to be
distance and I'm using it simply like so
without any scaling because I know the
distance of the sensor is going to be
four to two hundred centimeters based on
the datasheet lastly there's a 100
millisecond delay function to make sure
we are not over utilizing the sensor so
you have any doubts on how to on what
this is doing I'm going to essentially
put a link on the screen for the PWM
tutorial so feel free to review that
let's take a look at some of the
connections that we need to make in
order for this all of this to function
so I will post a schematic of what I've
actually connected but just quickly over
viewing I'm breaking out the 5 volts and
the ground onto the rails of the
breadboard so I have 5 volts and ground
going to the sensor as well as in 9
which is the trade pin going to the
appropriate location and the echo pin as
well so wait as I've shown before you
have writing at the bottom which
indicates which pin is what I have the
pin 6 of the Arduino go into the
Partizan positive side of the LED which
goes and the negative side goes through
the current limiting resistor which is
220 ohms in my case which goes back to
the ground so as you saw in my previous
slide I have already uploaded the
program so let's do some testing on the
sensor and as you notice
as I bring in my hand closer and closer
the LED should go dimmer and dimmer as I
move it back out it's going to be much
brighter and this goes up to 200
centimetres obviously it's going to be a
bit more difficult to demonstrate on the
camera
one thing you want to keep in mind with
these sensors is that they're not it's
not just a straight line which will be
detected you're going to be detecting a
sort of I kind of like a bulb
so it's an ultrasonic pulse which is
travelling in part versus let's say a
laser sensor or an infrared emitter so
there you have it the basic way of
detecting an obstacle using an
ultrasonic sensor the HC s are 0-4 in
this case so let me know if you have any
questions feel free to share the video
like comment and subscribe thank you bye