2021 May 04, 08:57 PM
I finally needed to replace the old sprinkler controller that has been in service for about 60 years. I had been using this dinosaur of a controller for over 20 years, and it's limitations finally prompted me to update. Of course I reviewed prices on new digital controllers from the leading irrigation controller manufacturers, but price and usability led me to this open source solution. I've included some pictures of the circa 1960 controller for your enjoyment.
The old controller had a nice weatherproof hardened enclosure, so I decided to remove the guts of that controller and use the enclosure for my SIP installation. The controller consists of a Raspberry Pi 4b with 3 amp USB-C modular power supply paired with a Huayao 8 Channel Optocoupled 5VDC Relay Module. Interfacing the Pi to the Relay Module was straightforward. I did not split the 5VDC supply on the Relay Board, choosing to drive the relay board entirely from the Pi 5VDC supply. I used the first 6 relays for the 6 existing stations in my existing irrigation configuration. I used the 7th relay as a Master for the 24VAC common line so that the solenoids are completely isolated from the 24VAC transformer when not activated.
I hardwired the Ethernet instead of using WiFi, mostly because my chosen enclosure is effectively a Faraday cage.
I salvaged the 24VAC transformer and 3A circuit breaker from the old controller. I used the existing 110VAC main running to the enclosure for the 24VAC transformer. I may add a extension cord socket pigtail to the 110VAC to plug my USC-C power block into; it's plugged into the GFCI quad outlet next to the enclosure now.
I 3D printed the white bracket to mount the Pi and Relay Board. I used long machine screws (M3) to mount the circuit boards to the bracket, with the head of the screw on the top side of the circuit boards, a nut on the back side of the circuit board, then sandwiched the bracket to the screw with another pair of nuts. So 8 M3 screws and 24 M3 nuts. The mounting holes on the Relay Board are 3mm. The mounting holes on the Pi are 2.5mm. The M3 screws installed on the Pi with a tight fit, tapping threads into the circuit board with the screw didn't appear to damage the circuits or components and the head and nut have adequate clearance from the components on the board, although less clearance than the appropriate M2.5 screws and nuts would have. I used metal screws and nuts. If I was less anxious to assemble this project, I would have purchased the appropriate size screws for the Pi, and probably would have used nylon instead of metal.
My wife is the primary user of the system. She's happy with it so far. She likes the interface. She says it intuitive. She asked a few questions about manual operation and she wants to be able to set the start time relative to sunrise. The manual operation was simple to explain. I've responded to a separate thread about setting start time relative to sunrise. I'm guessing it's going to take me a couple of weeks part-time to resolve that issue. Maybe there'll be another plugin available once I get it implemented.
I'm also looking at adding a water meter pulse interface to the Pi so I can set the station ON DURATION based directly on measured water volume instead of time.
I'm also looking at automatically adjusting station time/volume based on additional environmental inputs besides rainfall. In the desert southwest we have drastic shifts in humidity that effect evaporation rates. I want to be able to reduce water time/volume when the humidity is high resulting in less evaporation.
I'm excited about my new controller based on the Sustainable Irrigation Platform documentation and software. It was an easy build and setup.
My short term concerns with the new installation:
1. Will the Pi survive the heat? It gets up to 120°F in the shade here. My Pi has head sinks attached, but no fan. The enclosure is in the shade 100% but has no ventilation, although it is large and not air tight on the bottom. Will I need to add a fan and vents for circulation?
2. Will it be durable? My last controller was 60 years old and still functioning as designed. I don't expect that type of durability on this setup, but it would be nice to get 20 years out of it.
The old controller had a nice weatherproof hardened enclosure, so I decided to remove the guts of that controller and use the enclosure for my SIP installation. The controller consists of a Raspberry Pi 4b with 3 amp USB-C modular power supply paired with a Huayao 8 Channel Optocoupled 5VDC Relay Module. Interfacing the Pi to the Relay Module was straightforward. I did not split the 5VDC supply on the Relay Board, choosing to drive the relay board entirely from the Pi 5VDC supply. I used the first 6 relays for the 6 existing stations in my existing irrigation configuration. I used the 7th relay as a Master for the 24VAC common line so that the solenoids are completely isolated from the 24VAC transformer when not activated.
I hardwired the Ethernet instead of using WiFi, mostly because my chosen enclosure is effectively a Faraday cage.
I salvaged the 24VAC transformer and 3A circuit breaker from the old controller. I used the existing 110VAC main running to the enclosure for the 24VAC transformer. I may add a extension cord socket pigtail to the 110VAC to plug my USC-C power block into; it's plugged into the GFCI quad outlet next to the enclosure now.
I 3D printed the white bracket to mount the Pi and Relay Board. I used long machine screws (M3) to mount the circuit boards to the bracket, with the head of the screw on the top side of the circuit boards, a nut on the back side of the circuit board, then sandwiched the bracket to the screw with another pair of nuts. So 8 M3 screws and 24 M3 nuts. The mounting holes on the Relay Board are 3mm. The mounting holes on the Pi are 2.5mm. The M3 screws installed on the Pi with a tight fit, tapping threads into the circuit board with the screw didn't appear to damage the circuits or components and the head and nut have adequate clearance from the components on the board, although less clearance than the appropriate M2.5 screws and nuts would have. I used metal screws and nuts. If I was less anxious to assemble this project, I would have purchased the appropriate size screws for the Pi, and probably would have used nylon instead of metal.
My wife is the primary user of the system. She's happy with it so far. She likes the interface. She says it intuitive. She asked a few questions about manual operation and she wants to be able to set the start time relative to sunrise. The manual operation was simple to explain. I've responded to a separate thread about setting start time relative to sunrise. I'm guessing it's going to take me a couple of weeks part-time to resolve that issue. Maybe there'll be another plugin available once I get it implemented.
I'm also looking at adding a water meter pulse interface to the Pi so I can set the station ON DURATION based directly on measured water volume instead of time.
I'm also looking at automatically adjusting station time/volume based on additional environmental inputs besides rainfall. In the desert southwest we have drastic shifts in humidity that effect evaporation rates. I want to be able to reduce water time/volume when the humidity is high resulting in less evaporation.
I'm excited about my new controller based on the Sustainable Irrigation Platform documentation and software. It was an easy build and setup.
My short term concerns with the new installation:
1. Will the Pi survive the heat? It gets up to 120°F in the shade here. My Pi has head sinks attached, but no fan. The enclosure is in the shade 100% but has no ventilation, although it is large and not air tight on the bottom. Will I need to add a fan and vents for circulation?
2. Will it be durable? My last controller was 60 years old and still functioning as designed. I don't expect that type of durability on this setup, but it would be nice to get 20 years out of it.