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Why Arduino Pro Mini is my favorite

When you first start learning about the Arduino environment – you typically use a breadboard for your projects. Gradually you will advance, and your projects become more permanent installations – and then you will have to find a replacement for the Arduino Uno R3 board. The Uno board is great for experimentation but not for permanent installations where you want to solder in the components.

I have tried many different Arduino boards but my preferred is the Arduino Pro Mini board – it offers the best flexibility and still is very cheap. I will describe the Arduino Pro Mini and give you some hints about what you should know when sourcing for a Pro Mini.

Introducing the Arduino Pro Mini

The Arduino Pro mini is based upon a ATmega328 MCU. The board is basically a miniaturized Arduino Uno even though it is much smaller –because only SMD (surface mount) components have been used. The size is only 33mm x 18 mm x 3mm – and it can easily be used for wearable projects and is an excellent replacement for the Arduino Lilypad.

The Pro Mini is priced to about 1,7$ on eBay – but I recommend that you look for reviews before you buy the cheapest.

The core of the Pro Mini is the ATMega328 that runs at 16Mhz in the 5V version and 8Mhz in the 3.3V version. The board cannot run stable at 16Mhz if you power it with less than 4V.

The board does not have an USB plug and requires an external FTDI serial programmer.
You might be asking why Arduino Pro Mini vs Arduino Nano – wouldn’t it have been easier just to use a Nano that has an onboard USB. And yes – sometimes it is easier to use the Nano, but the Nano has three drawbacks compared to the Pro Mini.

  • Arduino IDE Sketches can be larger on the Pro Mini – the Nano uses some of the sparse memory for the USB code / uploader
  • Pro Mini uses less power than a Nano – the USB chip is powered on all the time and uses power. Not a problem if you are using a DC power supply – but if you are running on a battery this becomes important
  • If you want to make a low volt project, then you will have to choose the Pro Mini since the Nano cannot run on 3.3V due to the USB chip

The 5V version of the Arduino Pro Mini can run on a range between 5-12V – if connected to the raw/vin pin. If you are powering LEDs directly from the board you never exceed the maximum total output of 150mA~200mA.

The Arduino Pro Mini has two LEDs are soldered in: Power and status, only the status LED can be controlled programmatically.

Technical data:

Microcontroller ATmega328
Voltage  5V and 3.3V
Input min/max 5-12V and 3.3-12V
Digital I/O Pins 14 (6 with PWM support)
Analog Pins 8
Max. mA per I/O Pin 40 mA
Flash Memory 16 KB (2 KB by the bootloader)
SRAM 1 KB
EEPROM 512 bytes
Speed / Frequency 16 MHz / 8MHz

Inputs and outputs:

Schematic of Arduino Pro mini
Arduino Pro Mini schematic

Serial: Pins 0 (Rx/Receive) and 1 (TX/Send) are used to receive and send serial data.

Interrupts: External Interrupts can be triggered via pins 2 and 3. For this to work you must configure them appropriately using the function AttachInterrupt(). Interrupts are triggered by low level, falling, raising edge and value change.

PWM (pulse width modulation): Pins 3, 5, 6, 9, 10, and 11 provide 8-bit PWM (see function AnalogWrite()).

I2C (TWI): This interface required 2 lines. These are located on the analogue pins A4 (SDA) and A5 (SCL). The interface is supported by the Wire library.

SPI (Serial Peripheral Interface): This interface is located on pins 10 (SS), 11 (MOSI), 12 (miso) and 13 (SCK). This SPI is provided by hardware of the microcontroller, but special support in Arduino language is not available.

The board does not have a ICSP connection. If you need this (to connect the programmer), you need to use the corresponding pins directly.

Sensor Pro Mini

Sensor Pro Mini - lots of options and still small
Sensor Pro Mini – lots of options and still small

The Arduino Pro mini is available in a special Arduino Pro Mini Expanded version where you have extra soldering holes for sensor – this is truly practical and I highly recommend this board.

When you have a pin layout as the sensor board, you will get a much more clean build since you don’t have to add extra wires to voltage and ground connections.

I have used the Arduino Pro Mini sensor boards for a lot of projects – and especially for RC this board is a winner.

What do you think? Leave a comment below.

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