DIY Arduno "Ohmeter" + 0.96" OLED Display +Indication LEDs + Custom PCB

The “Crius Resistor Tester” is a handy little Gadget I made for my projects that help me measure the value of a Resistor.

The logic behind its operation and the code as far as I can understand and I AM NOT PROFESSIONALLY Electronics or Physicist, is Ohm's Law.

If you notice in the circuit below we use a 10kOhm resistor and 1 position for the resistance we want to measure.

Knowing the value of one resistor in a circuit with 2 resistors we are looking for the value of the second resistor.

From Wikipedia, the free encyclopedia :

Ohm 's Law ( in English Ohm's Law ) connects Voltage , Current and Resistance . There are two Ohm's laws, the open - circuit Ohm's law referred to a resistor [1] and the closed-circuit Ohm 's law .
The voltage source , V , drives the electric current , I , through the resistor , R. The three quantities obey Ohm's law: V = IR .
Ohm's Law in the Wikipedia article .

Supplies

For the project we will need :

Crius Resistor Tester PCB x1
Arduino Nano v3 (no headers) x1
SSD1306 I2C OLED Display 0.96” x1
1 Resistors 10kΩ x1
Red LED 3mm x1
Green LED 3mm x1
4 Pins Female Headers (2.54) x1
Male Pin Headers (for Arduino Nano) x30

Step 1: Solder 4 Male OLED Pins to PCB

I'll start by soldering the 4 male pins for the OLED display to the front side of the PCB.
We can tape them with some tape to hold them in place, so that we turn the board upside down and solder them.

Step 2: Solder Arduino Nano to PCB

Now we will place the Arduino Nano on the front side of the PCB (with the USB port to the left).
It is good to start soldering the Pins located in the corners because it helps to stabilize the board in order to solder the rest of the Pins easier.
Now with a cutter we will cut the Pins close to the board so that they do not extend, so that we can solder the OLED screen on top of them.

Step 3: Solder the LEDs

It's time to solder the 2 LEDs to the places labeled RED LED and GREEN LED on the PCB.

CAUTION!!!

You must solder the short Pin of the LEDs which is the Ground Pin to the square Pad on the PCB on the left for each Pin.

We can bend the Pins down to keep the LEDs from moving when we flip the PCB upside down in order to
solder them
Then I will cut off the pins that extend from the PCB.

Step 4: Solder the 10k Resistor to PCB

In the place named R1 on the PCB we will solder the 10kOhm resistor

We will bend the Pins on the back down to flip the PCB upside down
and solder it.

I almost always cut off the pins that protrude from the PCB so that they don't touch somewhere and cause a problem.

Step 5: Desolder OLED Pins

Now it is good to desolder the Pins that are stuck on the OLED screen that we will use in our project.

I will use the soldering iron with a wide tip to heat all the Pins at once
and pull them out with a pair of pliers when their solder joint melts.

Step 6: Solder OLED Display to PCB

Let's solder the OLED screen to the large side of the PCB, to the 4 male Pins that we had stuck at the beginning.
If there is solderleft from before and we cannot place the OLED screen on the male Pins, we can try heating for a few seconds (2-3) with a large tip all the Pins together, to melt the solder and push it down to the Pins so that we can solder it afterwards.

Step 7: Solder Female Pin Headers

Now it remains for us to solder the female Pin Headers to the PCB.

In case you have female Pin Headers with more Pins, cut with a cutter carefully NEXT to the line that separates the Pins.

To be able to solder them to the PCB we will have to remove the 2 middle Pins with a pair of pliers, pulling them carefully.
We can fix the Pin Headers with some tape on the PCB ,so we can flip it over and
solder the Pins.
Finally, cut the pins that protrude from the PCB

and practically...

THE PCB IS READY!!!

Step 8: Upload the Code

To upload the code to the Arduino, you should download the Arduino IDE from the Arduino site: https://www.arduino.cc/en/software
After installing the Arduino IDE, open the CRIUS_Resistor_Tester.ino file but BEFORE pressing Upload to pass the code to the Arduino
We should install 2 Libraries :

The Adafruit GFX
and the Adafruit SSD1306

from the menu Tools -> Manage Libraries… -> and typing for each one its name in the search bar that will appear in the window by pressing Install

Then we have to select Board from the menu Tools -> Board -> Arduino Nano
And the Port from the menu Tools -> Port -> the port we have connected the Arduino
Now we can press Upload and upload the code.