Peter's electronic projects

Electronic period timer based on PIC

version 1, 2001/07/06
designed by Peter JAKAB

NOTE for beginners: PICs are general purpose microcontrollers which have to be programmed before you can use them in the actual circuit! Check out this link to learn more.

description

This is a simple one-valve irrigation controller made for our greenhouse. The code contains a software real-time clock (RTC) and a multiplexed 8-digit LED display and keyboard you can use in other projects.

software, operation

The operating software is simple, it contains a real-time clock and a day counter. The valve is turned on in regular intervals in the same time. Day setting specifies the number of days between the activations, time setting specifies the time of the day when to start. Duration is the time after which the valve will be turned off.

• MODE button cycles through clock, start time and duration settings
• the interval and starting time set will be stored in the DATA EEPROM
• Scheduling can be totally turned OFF by the ENABLE button
• Irrigation can be manually turned ON/OFF any time by the START/STOP buttons
• Activation/STOP time is displayed in the second line of display
• Valve state (ON/OFF) is displayed in the second line, last dot

The source code is freely downloadable. This is written for the PIC16F84, but you can easily adapt it to newer controllers like the 16F628 or OTP versions.

schematic diagram

click to zoom

components