The Arduino Pro Mini is a compact microcontroller board based on the ATmega328P. Designed by Mine, it is ideal for embedded applications and prototyping where space and power efficiency are critical. Its small form factor and low power consumption make it a popular choice for wearable devices, IoT projects, and battery-powered systems.
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This circuit features an Arduino Pro Mini microcontroller interfaced with a USB Serial TTL for programming and power, a momentary switch for user input, and a 9V battery for power supply. It includes a KY-008 laser emitter, a 0.96" OLED display, and an MLX90614 temperature sensor, all connected to the Arduino for a potential temperature measurement and display application.
This circuit features an Arduino Pro Mini connected to an OLED display via I2C communication (SDA and SCL lines). The Arduino is also interfaced with an MCP2515 CAN controller, indicating the circuit's capability to communicate over a CAN network. Additionally, there are several terminal PCBs connected to various analog and digital pins of the Arduino, likely for sensor inputs or output controls.
This circuit features two Arduino Pro Mini microcontrollers interfacing with various sensors and actuators. One Arduino reads data from an ADXL345 accelerometer and communicates with an RS232 module, while the other controls a 2-channel relay to manage two 12V LEDs, a 1-channel relay to control a red lamp, and a buzzer. Power is supplied by 9V and 12V batteries.
This circuit features an Arduino Pro Mini as the central microcontroller, interfaced with a DS18B20 temperature sensor, a GPS NEO 6M module for location tracking, an ADXL345 accelerometer for motion detection, and an NRF24L01 module for wireless communication. The Arduino is powered by a 18650 Li-Ion battery through a voltage regulator, ensuring a stable power supply. A pushbutton is connected to the Arduino for user input, and resistors are used for pull-ups and current limiting purposes.
The Arduino Pro Mini is available in two voltage and clock speed variants: 3.3V/8MHz and 5V/16MHz. Below are the key technical details:
General Specifications
Parameter
Value (3.3V Variant)
Value (5V Variant)
Microcontroller
ATmega328P
ATmega328P
Operating Voltage
3.3V
5V
Clock Speed
8 MHz
16 MHz
Flash Memory
32 KB (0.5 KB used by bootloader)
32 KB (0.5 KB used by bootloader)
SRAM
2 KB
2 KB
EEPROM
1 KB
1 KB
Digital I/O Pins
14 (6 PWM outputs)
14 (6 PWM outputs)
Analog Input Pins
8
8
DC Current per I/O Pin
40 mA
40 mA
Dimensions
18 mm x 33 mm
18 mm x 33 mm
Pin Configuration and Descriptions
The Arduino Pro Mini has a total of 24 pins, including power, digital, and analog pins. Below is the pinout description:
Pin Name
Description
RAW
Unregulated input voltage (up to 12V). Internally regulated to 3.3V or 5V.
VCC
Regulated 3.3V or 5V output, depending on the board variant.
GND
Ground pin.
TX (D1)
Transmit pin for serial communication (UART).
RX (D0)
Receive pin for serial communication (UART).
D2-D13
Digital I/O pins. Pins D3, D5, D6, D9, D10, and D11 support PWM.
A0-A7
Analog input pins. Can also be used as digital I/O pins.
RST
Reset pin. Pull low to reset the microcontroller.
Usage Instructions
How to Use the Arduino Pro Mini in a Circuit
Powering the Board:
Use the RAW pin to supply unregulated voltage (up to 12V). The onboard regulator will convert it to the appropriate operating voltage.
Alternatively, supply regulated voltage (3.3V or 5V) directly to the VCC pin.
Programming the Board:
The Arduino Pro Mini does not have a built-in USB interface. Use an external USB-to-Serial adapter (e.g., FTDI adapter) to program the board.
Connect the FTDI adapter to the Pro Mini as follows:
| FTDI Adapter Pin | Arduino Pro Mini Pin |
|------------------|----------------------|
| VCC | VCC |
| GND | GND |
| TX | RX |
| RX | TX |
| DTR | RST |
Uploading Code:
In the Arduino IDE, select the correct board variant (Arduino Pro or Pro Mini) and processor (ATmega328P (3.3V, 8MHz) or ATmega328P (5V, 16MHz)).
Choose the appropriate COM port for your FTDI adapter.
Write or load your sketch and click Upload.
Important Considerations and Best Practices
Ensure the voltage of your peripherals matches the operating voltage of the Pro Mini (3.3V or 5V).
Use a decoupling capacitor (e.g., 0.1 µF) between VCC and GND for stable operation.
Avoid drawing more than 40 mA from any single I/O pin to prevent damage to the microcontroller.
For battery-powered applications, use the RAW pin to connect the battery for efficient regulation.
Example Code for Arduino Pro Mini with an LED
The following example demonstrates how to blink an LED connected to pin D13:
// Blink an LED connected to pin D13
const int ledPin = 13; // Define the LED pin
void setup() {
pinMode(ledPin, OUTPUT); // Set pin D13 as an output
}
void loop() {
digitalWrite(ledPin, HIGH); // Turn the LED on
delay(1000); // Wait for 1 second
digitalWrite(ledPin, LOW); // Turn the LED off
delay(1000); // Wait for 1 second
}
Troubleshooting and FAQs
Common Issues and Solutions
Problem: The board is not detected by the Arduino IDE.
Solution: Ensure the FTDI adapter is properly connected to the Pro Mini. Check the COM port settings in the Arduino IDE.
Problem: Code upload fails with a "not in sync" error.
Solution: Verify that the correct board and processor are selected in the Arduino IDE. Ensure the FTDI adapter's DTR pin is connected to the Pro Mini's RST pin.
Problem: The board overheats during operation.
Solution: Check the input voltage on the RAW pin. Ensure it does not exceed 12V. Verify that the current drawn by peripherals is within safe limits.
Problem: Analog readings are inaccurate.
Solution: Ensure the reference voltage is stable. Use a decoupling capacitor if necessary.
FAQs
Q1: Can I use the Arduino Pro Mini without an FTDI adapter? A1: Yes, you can use other USB-to-Serial converters or program the board using an ISP programmer.
Q2: What is the difference between the 3.3V and 5V variants? A2: The 3.3V variant operates at a lower voltage and clock speed (8 MHz), making it more power-efficient. The 5V variant operates at 16 MHz and is compatible with 5V peripherals.
Q3: Can I power the Pro Mini directly with a LiPo battery? A3: Yes, you can connect a single-cell LiPo battery (3.7V) to the RAW pin. The onboard regulator will handle the voltage.
Q4: Is the Arduino Pro Mini compatible with Arduino shields? A4: No, the Pro Mini does not have the standard Arduino shield form factor. However, you can use jumper wires to connect shields or peripherals.
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