Hi, in this episode I will demonstrate how
to make a simple,
but quite accurate Arduino ohmmeter.
This project requires only few components:
an Arduino, a breadboard, 3 jumper wires and
a few resistors.
You will also need a multimeter.
Let's build it and I will show you how it
works.
Connect the first jumper wire to the breadboard
and to the 5V pin on you Arduino board.
Another wire goes between the breadboard and
pin A0 on the Arduino.
Hook up the last jumper wire to the breadboard
and to the GND pin on the Arduino.
Grab a resistor,
measure its exact resistance
with a multimeter and remember the value.
It will serve as a reference resistor.
Connect it between the 5V and A0 wires.
Go to my website and download the Arduino
code for this project.
You will find the link in the description below.
Open the file and change this value to your
measured reference.
In my case it's 999 ohms.
You can now hook up your Arduino to the computer
and upload the code.
Now, it's time to connect the resistor we
wand to measure.
Connect it between the A0 and ground wires
on the breadboard.
To check the readings go to 'Tools' → 'Serial
Monitor'.
As you can see the values are very close when
compared to my multimeter.
Let's check another resistor.
This value is pretty close to the multimeter
too, but not as close as the previous one.
Let's see one more resistor.
This time the reading is rather inaccurate.
It turns out that the closer your tested resistor's
value to the reference,
the higher accuracy you can get.
If you require very precise results, you can
use
more reference resistors for different ranges, like in a multimeter.
But how does this Arduino rig work?
It is based on a simple voltage divider made up of 2 resistors,
which are connected between 5V and GND.
We know the exact resistance value of this
reference resistor and we know the input voltage,
which is 5V.
Arduino pin A0 can sense the output voltage
between these 2 points,
which is a fraction of the full 5V.
The rest of the magic is done by this formula,
which gives you the resistance of the test resistor.
Now you know how to measure resistance with
the Arduino.
If you have a question or want to add something,
feel free to leave a comment, send me a message
on Facebook, Twitter, or use the contact form
on my website.
I will reply to all of you.
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Thanks for watching and see you next time.
