Smart sprinkler on a Pan/Tilt mount to programmatically water the lawn with a fill pattern

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We all know how much precious water is wasted by lawn irrigation systems. While there are many sprinkler controller and irrigation projects on already, I want to do things a little different. While most other projects focus on controlling standard sprinkler systems that tend to spray wherever they please (mostly on driveways and sidewalks it seems), I want to experiment with a different way of watering: by controlling a single spray head to pattern the lawn, like a person would.
So whether you read "PTSprinkler" as Pan/Tilt, Polygon Trace or Pretty Terrific Sprinkler, the goal is first of all to cover the lawn area accurately, then make it smart with weather data and/or sensors.

The intention of this project is to use as many low cost off-the-shelf components as possible. Starting out with the lowest cost heavy duty outdoor pan/tilt stage I could find, plus a regular irrigation solenoid valve. Both parts are well-reviewed and are outdoor rated, so I don't need to try and re-invent the mechanical parts.

I will probably build some custom electronics to control these components from a Raspberry Pi.

The idea for setting it up is that the user would turn on the water and then manually control the valve, guiding it along the outline of the polygon that makes up the boundary of the area to be watered. Software would then simplify the polygon and calculate a fill pattern (or maybe two fill patterns crossed for better coverage), and move the spray along the calculated pattern across the lawn, taking into account the wider, less dense spray in the distance compared to the narrow, hard spray close to the spray head.

The goal is to cover the lawn evenly, and reduce overspray on sidewalks and driveways as much as possible, to use the minimal amount of water necessary to achieve the goal of keeping my lawn green through the summer. Other smart features such as scheduling based on time and weather forecast, integration with humidity sensors etc. may be added as the project progresses, but the first goal is even, accurate watering to significantly reduce waste associated with traditional sprinkler systems.

  • Dissecting the pan/tilt stage

    Patrick Van Oosterwijck6 days ago 0 comments

    I decided to play with the pan/tilt stage, below is the little bit of info that came with the device:

    Then I did some testing to see how it all behaves. At Tinkermill I have access to a nice isolated AC supply to do this:

    I was surprised how quiet the unit is! I was curious what kind of motors were used. I have been wondering if it will be necessary to add some position feedback to the unit or if I can just drive it for a certain amount of time and expect a certain amount of travel that is consistent. So I decided to dissect it and see what is inside. Here are some shots after disassembly:

    I couldn't find any info about the motors on the internet unfortunately. I can tell that they have four leads. That, plus the PCB with 2 capacitors makes me think that these are Permanent Split Capacitor motors. Since this is an induction type motor, there is unfortunately always slippage so the motor speed will vary with load and is not fixed at line frequency.

    I will have to see if this leads to problems where I will have to add position feedback or not. For now, I intend to just rely on the limit switches that are built in to the stage. I do not have direct access to these switches, but I intend to just move the pan and tilt in one direction for a while so both axes will be at their calibrated positions and then go from there based on timing. I'll have to see how quickly position will start to drift and if it's acceptable or if position feedback will have to be added.

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Patrick Van Oosterwijck wrote 4 days ago point

Yes that should work!  Once the pan/tilt stage control is done it can be used for all kinds of things.

My plan is to make a HAT with triac drivers for the pan/tilt stage and 24VAC to 5V converter to power the Pi that I want to use to prototype this.

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ken conrad wrote 4 days ago point

Nice! I would love to integrate this with my RasPi Rangefinder/Tracking system to keep the deer out of my garden!!

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