Electronic irrigation controller 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

name	value
DIS0-DIS7	common-anode 8x1-digit or 4x2-digit 7-segment LED display
TR1	mains transformer, 1x220VAC, 2x12VAC
-	24VAC irrigation valve
K1	12VDC relay. Contacts: >=1A
Q1-Q10	10xBC547A or similar NPN bipolar transistor
IC1	CD4017N
IC2	PIC16F84 or PIC16F84A microcontroller, programmed
IC3	7805 voltage regulator with heatsink
AC1	diode bridge at least 80V/1A
X1	4MHz crystal
R1, R17	2x10k
R18	1k
R19	S14K275 varistor
C1, C2	2x15pF
C3, C4	2x100nF
C5	1000uF/25VDC
D1-D4	4x1N4148
S1-S4	4xpush buttons
CN1-CN4	connector
F1	fuse 0.1A T
misc	PCB, housing