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It is an Arduino UNO board without any circuit board.

It uses a technology called freeform to interconnect components using wires or copper instead of a circuit board. It looks minimalistic and beautiful!

Why did I make this? I often find it hard to explain what freeform electronics are and what they look like. And Freeduino is a great example of freeform electronic art, easily comparable to the well-known device Arduino UNO, so I made it.

You can check out the previous LED pendant to learn the basics of brass welding, the tools, and materials needed.

Before we start soldering, we need to understand the functions of the various parts of the Arduino UNO. It can be roughly divided into 4 blocks:

ATmega328 MCU

ATmega328P PDIP

16MHz oscillator

Debounce capacitor

Power circuit

7-12V to 5V voltage regulator

5V to 3.3V voltage regulator

USB/input jack auto-selection circuit

Reverse current protection

USB to UART circuit

USB connector

Serial converter chip (ATMEGA8U2-MU) with oscillator and debounce capacitor

Signal light

Power indicator light

Default LED (D13)

TX/RX LED

First, we start with the MCU and the digital and analog IO pin connectors. The Arduino UNO has a clever pin layout that matches very well with the layout of the ATMEGA328 28-DIP package. Therefore, no cross wires are needed.

The only external component for the ATmega328 to function is an external 16MHz oscillator that requires two 22pF capacitors. The hardware of the ATmega328P is minimal. It can now be tested for the first time via the AVR ISCP interface with the USBasp programmer.

I made a special fixture for myself to hold the pin socket in the right position, leaving enough space for soldering.

The ATmega328 is powered by 5V. The Arduino UNO has two power input sources – a jack (7-12V) or a USB connector (5V). It also provides 3.3V power for external components. This means two voltage regulators are needed. First, convert 7-12V to 5V, and then convert 5V to 3.3V. Following the recommendations in the datasheet, I used two AMS1117 5V and 3.3V voltage regulators along with some capacitors.

To simplify operations, I soldered the power circuit to the outside of the board and then placed it on the data line. This actually created two layers of freeform circuits. I omitted the auto-selection and reverse current protection parts because they would make the entire process very complicated. Unless you are dissatisfied with the board, you can do without them.

This is important if you want to upload programs through the Arduino IDE without relying on a compiler. Well, it wouldn’t be as cool without it. The original Arduino UNO R3 uses ATMEGA8U2-MU, which is great but too small for freeform circuits. I decided to go with the CH340C chip. It has a suitable SOP-16 package and only requires four external components – a debounce capacitor, a reset capacitor, and two Tx/Rx line resistors. The fact that no external capacitors are needed greatly simplifies the entire circuit.

I don’t like those large THT LEDs, so I decided to use small SMD 1206 LEDs to emit power, L, Tx, and Rx communication signals. I regret it. I first soldered an SMD resistor to them and then tried to solder it to the wire. This was tricky. I had to use a low-temperature soldering iron and solve the problem as quickly as possible, or the other side of the SMD component would come off.

First, I connected the external power supply to check the power regulator. All voltage levels were good, so I continued with the connections and uploaded the bootloader program to the chip via the USBasp programmer. To my surprise, the chip communicated on the first attempt. That was a good sign. The external crystal oscillator worked normally, and all pins were connected correctly. The last step was to connect the USB cable and try to upload the blink program. Let’s see:

Now, I encased it in transparent resin to make it less fragile.

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