connected to both RA0 and RA1 through signal diodes
D1 and D2. When the Enter switch is activated, it pulls
both RA0 and RA1 low at the same time. This allows two
I/O pins to interface three input switches.
The signal diode D1 prevents the Left switch from also
pulling RA1 low because it is reversed-biased. Likewise,
D2 prevents the Right switch from pulling RA0 low. RA0
and RA1 are also configured to cause an interrupt
whenever one or both of them go to a logic zero.
Critical to the operation of the Irrigation Watch is the
sensing of water flow to the irrigation system, which is
accomplished with a Hall effect water flow sensor shown
20 September 2017
REF QTY DIGI-KEY PT# MANUFACTURER PT# DESCRIPTION
R1-4 4 1.2KWCT-ND FMP100JR-52-1K2 RES 1.2K OHM 1W 5% AXIAL
R5 1 3.3KQBK-ND CFR-25JB-52-3K3 RES 3.3K OHM 1/4W 5% AXIAL
Q1 1 2N3904FS-ND 2N3904BU TRANS NPN 40V 0.2A TO-92
D1-2 2 1N914B-ND 1N914B DIODE GEN-PURP 100V 200 MA DO35
C1-4 4 399-4151-ND C315C104M5U5TA CAP CER 0.1 μF 50V Z5U RADIAL
RL1 1 HE113-ND HE721C0510 RELAY REED SPDT 250 MA 5V
RV1 1 3362P-103LF-ND 3362P-1-103LF TRIMMER 10K OHM 0.5W PC PIN
S1 1 458-1342-ND PK-11N40PQ AUDIO PIEZO INDICATOR 3-5V TH
U1-4 4 160-1350-5-ND LTV-814H OPTO-ISOLATOR 5 KV TRANSISTOR 4-DIP
U5 1 PIC16F1829-I/P-ND PIC16F1829-I/P IC MCU 8-BIT 14 KB FLASH 20-DIP
DS1 1 67-1779-ND LCM-S01602DTR/A LCD MODULE 16x2 DISPLAY
SW1-3 3 6 x 6 x 12 mm PCB mount momentary four-pin pushbutton tactile switch
P1 1 .100 Pitch six-pin right angle header
P2 1 .100 Pitch three-pin right angle header
P3 1 2. 54 mm pitch 10-pin straight pin PCB screw terminal block connector
Hall effect water flow sensor; working range 1-30 L/min, model YF-B5.
Enclosure, DIY 86 plastic project shell for DIY meter tester kit LCD1602 with buttons.
#4-40 hardware for mounting display and circuit board.
■ PHOTO 1. Close-up view of installed water flow
sensor. This sensor has male hose connections, so I used
two female hose to female pipe connectors on each
end. Note the working range and model number.
■ PHOTO 2. Water flow sensor installed in water line
that feeds my irrigation system. Note water cut-off
valves on either side.
The 16x2 LCD display can be purchased on eBay from a China
supplier for as little as $1.60 each including shipping. Shipping
can take a few weeks. The display can also be found from US
suppliers at a higher cost, but will ship much faster.
The pushbutton switches were purchased on eBay from
“22newcentury.” Search "6x6x12 mm PCB Mount Momentary
Four-Pin Pushbutton Tactile Switch w Green Cap."
The 2. 54 mm pitch 10-pin screw terminal connectors were
purchased on eBay from “2015hiworld.” Search " 2. 54 mm Pitch
10 pin Straight Pin PCB Screw Terminal Block Connector."
The Hall Effect water flow sensor was purchased on eBay from
“royalwaytrade.” Search "G3/4 Threaded Water Hall Flow
Sensor Switch Flow Meter Water Control Copper," or just
search "Hall Effect Water Flow Sensor." I think this is an
industrial part used in vending machines.
The enclosure was purchased on eBay from “yelloweagle1991.”
Search "DIY 86 Plastic Project Shell For DIY Meter Tester Kit
LCD1602 With Buttons."