30 min

Optimize your electrical control systems with J1031C3VDC and PIC18F86J15

Lights, heaters, motors, oh my! SPDTs for all your needs.

Relay 4 Click with UNI-DS v8

Published Oct 18, 2023

Click board™

Relay 4 Click

Development board



NECTO Studio



Count on our SPDT relays to seamlessly switch between two different circuits, ensuring your devices operate efficiently and effectively



Hardware Overview

How does it work?

Relay 4 Click is based on dual J1031C3VDC, high-current single-pole double-throw (SPDT) signal relays from CIT Relay and Switch. The J1031C3VDC relay is well known for its reliability and durability, high sensitivity, and low coil power consumption housed in a small package with PC pin mounting. Despite its size (12.5x7.5x10 millimeter (LxWxH)), the J1031C3VDC relay can withstand up to 2A and 125VAC/60VDC maximum. These relays are designed to easily activate their coils by relatively low currents and voltages, making them a perfect choice that any MCU can control. As mentioned, the contact configuration of the J1031C3VDC is a single-pole double-throw (SPDT), meaning it

has one pole and two throws. Based on the default position of the pole, one throw is considered normally open (NO) while the other is normally closed (NC), which is, in this case, its default position. When the coil is energized, it will attract the internal switching elements similar to a switch. This Click board™ uses two mikroBUS™ pins for its proper operation, the RL1 and RL2 pins routed to the RST and PWM pins of the mikroBUS™ socket. These pins control small N-channel MOSFET RET (Resistor Equipped Transistor) transistors that provide enough current for the relay coil. Two resistors are already integrated into the RET, providing the correct biasing and simplifying the

design. Also, each relay has its yellow LED indicator, which signals the state of the relay. When the current flows through the RET, the coil will be energized, and the relay will be switched from a closed to an open switch state. This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. Also, it comes equipped with a library containing functions and an example code that can be used as a reference for further development.

Relay 4 Click hardware overview image

Features overview

Development board

UNI-DS v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports a wide range of microcontrollers, such as different STM32, Kinetis, TIVA, CEC, MSP, PIC, dsPIC, PIC32, and AVR MCUs regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer over WiFi. The development board is well organized and designed so that the end-user has all the necessary elements, such as switches, buttons, indicators, connectors, and others, in one place. Thanks to innovative manufacturing technology, UNI-DS v8 provides a fluid and immersive working experience, allowing access anywhere and under any

circumstances at any time. Each part of the UNI-DS v8 development board contains the components necessary for the most efficient operation of the same board. An advanced integrated CODEGRIP programmer/debugger module offers many valuable programming/debugging options, including support for JTAG, SWD, and SWO Trace (Single Wire Output)), and seamless integration with the Mikroe software environment. Besides, it also includes a clean and regulated power supply module for the development board. It can use a wide range of external power sources, including a battery, an external 12V power supply, and a power source via the USB Type-C (USB-C) connector. Communication options such as USB-UART, USB

HOST/DEVICE, CAN (on the MCU card, if supported), and Ethernet is also included. In addition, it also has the well-established mikroBUS™ standard, a standardized socket for the MCU card (SiBRAIN standard), and two display options for the TFT board line of products and character-based LCD. UNI-DS v8 is an integral part of the Mikroe ecosystem for rapid development. Natively supported by Mikroe software tools, it covers many aspects of prototyping and development thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.

UNI-DS v8 horizontal image

Microcontroller Overview

MCU Card / MCU



8th Generation



MCU Memory (KB)


Silicon Vendor


Pin count


RAM (Bytes)


Used MCU Pins

mikroBUS™ mapper

Relay 1 Control
Power Supply
Relay 2 Control

Take a closer look


Relay 4 Click Schematic schematic

Step by step

Project assembly

Fusion for PIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the UNI-DS v8 as your development board.

Fusion for PIC v8 front image hardware assembly
GNSS2 Click front image hardware assembly
SiBRAIN for PIC32MZ1024EFK144 front image hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
v8 SiBRAIN Access MB 1 - upright/background hardware assembly
Necto image step 2 hardware assembly
Necto image step 3 hardware assembly
Necto image step 4 hardware assembly
NECTO Compiler Selection Step Image hardware assembly
NECTO Output Selection Step Image hardware assembly
Necto image step 6 hardware assembly
Necto image step 7 hardware assembly
Necto image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Necto PreFlash Image hardware assembly

Track your results in real time

Application Output

After pressing the "FLASH" button on the left-side panel, it is necessary to open the UART terminal to display the achieved results. By clicking on the Tools icon in the right-hand panel, multiple different functions are displayed, among which is the UART Terminal. Click on the offered "UART Terminal" icon.

UART Application Output Step 1

Once the UART terminal is opened, the window takes on a new form. At the top of the tab are two buttons, one for adjusting the parameters of the UART terminal and the other for connecting the UART terminal. The tab's lower part is reserved for displaying the achieved results. Before connecting, the terminal has a Disconnected status, indicating that the terminal is not yet active. Before connecting, it is necessary to check the set parameters of the UART terminal. Click on the "OPTIONS" button.

UART Application Output Step 2

In the newly opened UART Terminal Options field, we check if the terminal settings are correct, such as the set port and the Baud rate of UART communication. If the data is not displayed properly, it is possible that the Baud rate value is not set correctly and needs to be adjusted to 115200. If all the parameters are set correctly, click on "CONFIGURE".

UART Application Output Step 3

The next step is to click on the "CONNECT" button, after which the terminal status changes from Disconnected to Connected in green, and the data is displayed in the Received data field.

UART Application Output Step 4

Software Support

Library Description

This library contains API for Relay 4 Click driver.

Key functions:

  • relay4_set_relay1_open - This function sets the relay 1 to normally open state by setting the RL1 pin to low logic level.

  • relay4_set_relay1_close - This function sets the relay 1 to normally close state by setting the RL1 pin to high logic level.

  • relay4_set_relay2_open - This function sets the relay 2 to normally open state by setting the RL2 pin to low logic level.

Open Source

Code example

This example can be found in NECTO Studio. Feel free to download the code, or you can copy the code below.

 * @file main.c
 * @brief Relay 4 Click Example.
 * # Description
 * This example demonstrates the use of Relay 4 click board by toggling the relays state.
 * The demo application is composed of two sections :
 * ## Application Init
 * Initializes the driver and logger.
 * ## Application Task
 * Switches the relays 1 and 2 state every 5 seconds and displays the state on the USB UART.
 * @author Stefan Filipovic

#include "board.h"
#include "log.h"
#include "relay4.h"

static relay4_t relay4;   /**< Relay 4 Click driver object. */
static log_t logger;    /**< Logger object. */

void application_init ( void ) 
    log_cfg_t log_cfg;  /**< Logger config object. */
    relay4_cfg_t relay4_cfg;  /**< Click config object. */

     * Logger initialization.
     * Default baud rate: 115200
     * Default log level: LOG_LEVEL_DEBUG
     * @note If USB_UART_RX and USB_UART_TX 
     * are defined as HAL_PIN_NC, you will 
     * need to define them manually for log to work. 
     * See @b LOG_MAP_USB_UART macro definition for detailed explanation.
    LOG_MAP_USB_UART( log_cfg );
    log_init( &logger, &log_cfg );
    log_info( &logger, " Application Init " );

    // Click initialization.
    relay4_cfg_setup( &relay4_cfg );
    RELAY4_MAP_MIKROBUS( relay4_cfg, MIKROBUS_1 );
    if ( DIGITAL_OUT_UNSUPPORTED_PIN == relay4_init( &relay4, &relay4_cfg ) ) 
        log_error( &logger, " Communication init." );
        for ( ; ; );
    log_info( &logger, " Application Task " );

void application_task ( void ) 
    relay4_set_relay1_open ( &relay4 );
    log_printf( &logger, " Relay 1 set to normally open state\r\n" );
    relay4_set_relay2_close ( &relay4 );
    log_printf( &logger, " Relay 2 set to normally close state\r\n\n" );
    Delay_ms ( 5000 );

    relay4_set_relay1_close ( &relay4 );
    log_printf( &logger, " Relay 1 set to normally close state\r\n" );
    relay4_set_relay2_open ( &relay4 );
    log_printf( &logger, " Relay 2 set to normally open state\r\n\n" );
    Delay_ms ( 5000 );

void main ( void ) 
    application_init( );

    for ( ; ; ) 
        application_task( );

// ------------------------------------------------------------------------ END

Additional Support