Do you want to play with circuits but don’t know how to design a PCB? You can! Before PCBs existed, components were connected directly (as imagined by Teacher Su). In fact, even when we have PCB design issues that require rework, we often use various jumper wires to make our circuits work.

So, even if your PCB design is flawless, occasionally DIYing a circuit without a PCB is also a meaningful endeavor.

Today, let’s take a look at a project done by a foreign expert on the Arduino Uno. Here is his work; let’s admire it for a moment.

First, let’s see what components are included in the Arduino Uno circuit and how they are connected.

Isn’t it quite complex? The expert divided these components into four parts:

ATmega328 MCU

• ATmega328P PDIP

• 16MHz Crystal Oscillator

• Capacitors

Power Circuit

• 7-12V to 5V Voltage Regulator

• 5V to 3.3V Voltage Regulator

• USB/External Input Auto Selection Circuit

• Reverse Current Protection

USB to UART Circuit

• USB Connector

• Serial Conversion Chip (ATMEGA8U2-MU), with Oscillator and Capacitors

Indicator LEDs

• Power LED

• Default LED (D13)

• TX/RX LEDs

The expert first handled the MCU and its connected data lines. Fortunately, the pin allocation of the external connector for the Arduino Uno matches the pins of the 28-DIP package of the ATMEGA328, which avoids unnecessary wiring crossings.

Below is the data connection of the MCU socket and IO connector.

The components surrounding the ATmega328 include a 16MHz crystal oscillator and two 22pF capacitors, as shown below:

Next, let’s look at the power circuit. The expert used a perforated board to create a support for sufficient soldering space.

The Arduino Uno has two power inputs:

• 5V DC via USB

• 7-12V DC from an external socket (By the way, Teacher Su asks everyone, why is it 7-12V? What happens if it’s below 7V or above 12V?)

There are two voltage regulators on the circuit, one providing 5V DC and the other providing 3.3V DC. In this project, the expert used the AMS1117-5 and AMS1117-3.3 voltage regulators, which are favored by engineers. Of course, these two regulators also require corresponding external capacitors, which are SMD packaged capacitors.

The expert actually made two layers of connections, similar to a double-sided PCB.

Now let’s take a look at the USB to UART circuit part:

This part is very important for configuring the board with the Arduino IDE without needing a dedicated programmer. Here, the chip used is CH340C. The original Arduino Uno R3 design used ATMEGA8U2-MU, but that was too small and difficult to solder here. CH340C is SOP-16 packaged, requiring only four external components – two capacitors and two resistors on the Tx/Rx lines, greatly simplifying the circuit complexity.

Indicator LEDs:

The expert used 1206 surface mount LEDs, as seen in the image below.

Everything is ready; connect the power, download the Bootloader, everything works fine, communication is normal, and download a blinking LED program, it works! Below is a screenshot from a video on YouTube.

Here is a comparison with the standard Arduino Uno product.

Finally, here are photos of the top and bottom of the finished product.

Cool, right? Why not try it yourself?