Sprinkler: Control System

[last updated: 2026-08-11]
Sprinkler System home page
RTC PCF8523
relay boards
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• Rev. 0:
  • Hardware:
    • Nano MCU
    • Nano drives Relay Board
      Relays directly switch 24vac to energize valves.
  • Software:
    Simple timer, some minutes on, some minutes off, only controlling 1 zone.
    sprinkler-03a.ino.txt

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• Rev. 1:
  • Hardware:
    Add RTC: PCF8523
    Add OLED
    Both use i2C communication

  • Software:
    Progress getting a queue management routine in the software,
    but then got error for OLED failing to initialize
    google says not enough memory.
    will need to go to something with more memory to accommodate the software I want to use.

    
    This rev abandoned.

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• Rev. 2:
  Hardware:
  • Investigating the Teensy 4.0 ...
  • Since the Teensy has on on-board RTC, this first rev will not use the external PCF8523
  • It may be necessary to use optoCouplers between the Teensy outputs and the relay board inputs
  • Keeping the OLED for local status readout.

  
  This rev set aside if not abandoned.

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• Rev. 3:
  • Back to minimal basics:
    just arduino interfacing to relay board.
  • No RTC, no OLED, no queuing software, just programmed to run two zones.

  • sprinkler-09.ino.txt
    Added HB back, and went down to discover it had locked up, after running continuously maybe two days. Further testing needed.

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• Rev. 4:
  • Expanded:
    Added RTC back, added PB for single-shot cycling.
    No queuing software, just hard-coded watering durations and times.
    Watering 4 zones.
    Current software: sprinkler_11m
  • Using FunDuino interface board, with RTC on a temporary daughter-board.

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• Future:
  • Hardware:
    • OLED readout on Nano?
    • RTC
    • outside temperature sensor
    • RS485 connection to rPi upstairs?
    • water pressure sensor

      go to: water pressure sensor

  • Software:
    • Sprinkler onTimeDurations and offTimeDurations
      will be adjusted according to algorithm
      that uses outside temperature input.
    • "Throttle valve" (proportional ball valve)
      % open is adjusted to accommodate variations in incoming water pressure

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eof