Fab Academy 2023

@ Fab Lab Rwanda, Kigali

Electronic Design :

Task: Use the test equipment in your lab to observe the operation of a microcontroller circuit board (as a minimum, you should demonstrate the use of a multimeter and oscilloscope); 🙈

For this assignemnt, we want to test the current provided by atmega328p which os arduino uno board. the arduino uno board we have is embedded with another development board tht has many sensors and actuators and even built-in LED that can be used for beginners in embedded programamming. lets test ohms law and how it is applied on microcontrolles

Ohm's law is a fundamental principle in electrical engineering that relates the current, voltage, and resistance in an electrical circuit. It states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points, and inversely proportional to the resistance between them. The mathematical equation for Ohm's law is:

    
        I = V / R

where I is the current in amperes (A), V is the voltage in volts (V), and R is the resistance in ohms (Ω).

This equation can be rearranged to solve for any one of the three variables, depending on what is known or being measured in the circuit. Ohm's law is commonly used to calculate the voltage, current, or resistance in a circuit, and is a fundamental principle in understanding the behavior of electrical circuits.

Use of Multimeter

what is a multimeter?

A multimeter, also known as a volt-ohm meter or VOM, is a versatile electronic device that can measure several electrical properties of a circuit. It typically measures voltage, current, and resistance, and may also include additional features such as continuity testing and diode testing

Arduino nano specs

Microcontroller ATmega328P
Operating Voltage 5V
Input Voltage (recommended) 7-12V
Input Voltage (limits) 6-20V
Digital I/O Pins 14 (of which 6 provide PWM output)
Analog Input Pins 8
DC Current per I/O Pin 20 mA
DC Current for 3.3V Pin 50 mA
Flash Memory 32 KB (ATmega328P), of which 2 KB used by bootloader
SRAM 2 KB (ATmega328P)
EEPROM 1 KB (ATmega328P)
Clock Speed 16 MHz

From that table above , i wanted to test whever the the output voltage of the microcontroller on any digital pin is 5V and also test the current that is offering when we supply the voltage to the LED and limiting resistor

Simulation with thinkercard

here i used arduino uno and i want to connect an LED on digital pin 13 of course with a limiting resistor having 220 ohm

Here you see that i am measuring the voltage accrss the resistor. when a pin goes high, the multimeter reads 2.45V and we know that the pin outputs 5V , SO why 2.45V instead of 5V? Because the rest is the forward voltage drop of the diode

The above picture shows that the total voltage of pin 13 I/0 is 4.44V which is different from theorical voltage which is 5V. The drop on resistor is 2.45V and the drop on LED is 2V . our simulation is perfect . lets now test the current

Here you see that the voltage is zero when pin goes Low
To measure the current . the multimeter should be put in amperage as show in the figure
The current is 11.1mA when the pin goes high. This shows that using the selected resistor , the current cannot go beyond recommended 20mA.
then it goes to zero when the pin goes LOW

Measuring with Multimeter

Current measurement . the total current frowing in the resistor is equals to 10.13mA. The multimeter is put in amperage mode
the voltage across the resistor is 2.2V. Meanng the rest is the voltage across the LED
Here the voltage across the LED is 2.8V. the total with resistor is equal to around 5V

Now lest measure the I/0 voltage

The following code is led blinking . the pin 13 is maintained high within 5 seconds and then i made measurement.
I measured pin 13 and ground when it is high then i findout 5v which is perfectly when i read on datashett.

Using oscilloscope

The following experiments is very simple. just checking the waveform of generated pwm signal on pin 30 of esp32

here the duty cycle was 50%
increased duty cycle

the following is the code used for testing

the code used
ESP32 with oscilloscope during testing

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