and now to something completely different..

I have some older automated lawn sprinkler installed in my garden. So when the respective controller started to misbehave my first reflex was to try and repair it.. but not having any real clue about electronics, this proved to be somewhat difficult, and with the limited functionality that the commercial product had offered in the first place, I reckoned that it wasn’t worth the effort anyway.

But being tired of performing the same manual irrigation round every one or two days during summer – not to mention the vegetable garden – I thought that it might be a fun little project to design a replacement tailored to my needs, while learning a thing or two about simple electronics.

irrigation project

What I wanted was a system that would not just stupidly irrigate based on some predetermined schedule, but a system flexible enough to adapt based on actual irrigation needs. Also I wanted to be able to collect (on my PC) all weather/irrigation related data so that I will be able to verify that the system actually has the desired effect. It should then be possible to interact with the system without having to rewire the garden. Obviously the system should continue to function (and not lose sensor data) while my PC is switched off.

Side note: As a general principle I am trying not to rely on WiFi at all, but the place where the irrigation is supposed to happen is also actually out of regular WiFi range (unless I were to use additional repeaters). I would have liked to use some powerline based approach but rejected that idee (for now) due to the added costs and engineering complexities. I am not interested in mobile phone based approaches either: First of all the whole point of this exercise is “automation”, i.e. I want to prepare for those moments where I am NOT at home (e.g. when I am on vacation) and where I do not have adequate information regarding which of my plants might be in need of irrigation. Having a phone (or web based) “remote control” for me therefore seems to be but a rather useless gadget. Finally I don’t want to pay for a respective phone contract (that I otherwise do not need) just to irrigate my garden.

This being my first baby-steps in the realm of DIY hardware, I wanted to use something as inexpensive as possible – so that it would not hurt financially regardless of how many electronics components I might fry due to my noobish ignorance.. I therefore decided to base my experiment on some cheap chineese Arduinos. These things cost about a Euro each such that the single most expensive component for all of my devices finally proved to be the plastic case used to package them..
devices

I ended up building three types of devices:
1) soil/air sensors: Equipped with a simple 433MHz transmitter these devices periodically broadcast their measurements, and various power saving techniques make sure that they’ll get through the season on their rechargable 9V battery.

2) RainMaker controller: This controls the irrigation valves (based on configuration and sensor data) and it also buffers and relays (to the PC) the data that comes from the sensors. It uses a somewhat more powerful transceiver for two-way communication with the PC.

3) USB interface: Simple device that is connected to the PC’s USB port. It allows the PC to communicate with the RainMaker device(s) in the field – or any other device that is based on my respective custom communication protocol.

When ordering the parts in small quantities from AliExpress the material costs for the different devices are: 10-12$ per sensor (depending on features), 12$ for the USB interface, 45$ for the RainMaker and another 45$ for the irrigation valves (6-way) assembly.

For the PC side I setup a simple DB to store sensor/irrigation data and I wrote a simple Java GUI used to visualize that data, and to interact with available devices in the field.

workbench_ov

So far I successfully completed the dry-testing, and it will be time to test the devices in the field.. where it remains to be seen what additional insights will come of that.

Lessons learnt so far..

  • With a bit of help from an electronics savy coach (thank you Markus! 🙂 ) doing a bit of DIY hardware can be a fun experience – even for electronics beginners.
  • As soon as a MickeyMouse project gets just a tiny bit “bigger” you may quickly run into the limitations of the inexpensive/smaller Arduino’s hardware (e.g. you want to use a receiver and an additional transceiver, a LCD, a RealtimeClock, some Relais and an EEPROM and you may run out of I/O pins; and even when you circumnavigate that issue (e.g. using I2C and some PISO shift register) you might find that your program – with all the required libs – just barely fits into the available 32k FLASH ROM). Except for very simple devices, optimizing your stuff for size seems to be a part of the Arduino deal. I had last encountered these kind of problems on the C64 some 30 years ago 🙂
  • What people seem to call an IDE in the Arduino world can be rather frustrating for anyone who is used to work with a real IDE (aka IDEA IntelliJ, etc). Calling it “AlmostNotepad” would be a more fitting description. Certainly you don’t want to make programming errors in that kind of environment.. ever 😉
  • Actually there is a friendly / supportive Arduino community that may considerably help you on your learning curve.
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Posted on May 8, 2016, in Arduino, C, Hardware, Java, Uncategorized. Bookmark the permalink. Leave a comment.

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