This is all just theory at the moment, thought I'd post it to my peers for review before I actually commence design (and maybe get some pointers).
So the idea:
I've got quite a few chilli plants growing outdoors at the moment and because of work I don't always get to water the bloody things (interstate trips etc..) - and the LOVE water and heat (Chillies are mostly tropical).
So the theory is to throw together a small (cheap-ish) monitoring system that will detect water levels and water (via electronic solenoid) accordingly.
Ultimately, to measure water content in the soil, and water it when required.
[The RPi and it's limiations]
I've got like 4 x RPi's laying around doing nothing (and a few more doing other tasks) so it just makes sense to utilise one of them for this project - but there are some caveats to take note of:
[Water supply]
[Overview]
Time to pick some components out and design my Control circuit board - To be continued...
All design ideas welcome! (This is a forum)
So the idea:
I've got quite a few chilli plants growing outdoors at the moment and because of work I don't always get to water the bloody things (interstate trips etc..) - and the LOVE water and heat (Chillies are mostly tropical).
So the theory is to throw together a small (cheap-ish) monitoring system that will detect water levels and water (via electronic solenoid) accordingly.
Ultimately, to measure water content in the soil, and water it when required.
[The RPi and it's limiations]
I've got like 4 x RPi's laying around doing nothing (and a few more doing other tasks) so it just makes sense to utilise one of them for this project - but there are some caveats to take note of:
- Real resistance/capacitance based water sensors are expensive! Try around the $70 mark +/-; Stainless-steel cutlery are rather inexpensive as long as I can 'tune' the ADC to desired level via trial and error (and re-tune every so often to accommodate for the unavoidable corrosion/oxidisation). As such I'll make the 'water sensors' a pair of fork prongs on a board coated with silicon gel (other ideas welcome!)
- The RPi is 3V3 Digital I/O only - no ADC exists so an external ADC will have to be used. What the RPi does have is a couple of I2C channels so an I2C-based ADC I/O expander would be ideal - but that also yields some distance issues because of the bus (1 meter is about the reliability of 3V3 I2C), now we're looking at I2C bus expanders to support the 10 meters or so from my plants to my shed.... This is quickly getting more complicated, perhaps an outdoor cabinet is the answer, and just run power from the shed... Hmm, that might be the go - Other ideas welcome.
- The RPi code is easy (That's my bread and butter)
- I intend to supply schematics, source code and photos.
[Water supply]
- 12/24v Irrigation water solenoids are also pricey, washing machine solenoids on the other hand are not, but they run on 240v which means relays, diodes and mains power (which isn't an issue).
- Water pressure is rather good in my house which means, depending on the outlets I use, could water next door's house or burrow a hole in the soil depending on where they're pointing. A flow-limiter will have to be employed.
[Overview]
- 2 Circuits boards are required as I see it now. One for the RPi I2C to DIO/ADC (Low voltage area) and one for the relay/diode solenoid control (High voltage). Interconnects will be modular - something in the molex range, like a USB header on a motherboard (and the RPi DIO header).
- 2 outdoor rated cabinets will be used, again separating the RPi and it's control circuits to the high voltage relays and solenoids.
Time to pick some components out and design my Control circuit board - To be continued...
All design ideas welcome! (This is a forum)
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