Programmable relays are key elements in numerous automation applications such as automatic street light control, watering and pump control, HVAC, home automation, power plants automation in industries, etc. This DIY programmable relay switch uses PIC16F1847 (PIC16F628A can also be used) microcontroller and allows you to set both ON and OFF times. It also features cyclic option, which means you can choose to run it in a continuous loop of ON and OFF cycles. The timer can be programmed through 4 push switches. The programming menu, relay status (ON or OFF), and number of cycles completed are displayed on a 16×2 character LCD. The timing resolution of this relay timer is 1 minute. The timer also saves the previously-set ON/OFF times and the cyclic option in its internal EEPROM so that it can retain these values after any power supply interrupt. The firmware for this project is provided for both PIC16F1847 and PIC16F628A microcontrollers.

Features

• On-board 5V voltage regulator (operates at 9-15V DC input)
• OFF and ON time setup for the relay operation
• Option for cyclic run (maximum 100 cycles, after which the timer stops automatically)
• Stores ON/OFF times and Cyclic option from previous setup into internal EEPROM
• ON/OFF timing range: 0 to 99 hours and 59 minutes with 1 min resolution
• Interactive user interface using 4 tact switches and a character LCD
• On-board buzzer alarm

Package list

• Programmable relay timer switch (PCB only) x1

Note that you will get PCB only and the complete list of the components, circuit details, and firmware are available at the document website. Document link: http://embedded-lab.com/blog/another-programmable-relay-switch-using-pic-mcu/