• Grow Update & Controller Problems

    Jared Sanson • 06/05/2016 at 20:48 • 0 comments

    Well despite the lack of proper automation (my controller is currently out of action while I fix the water level sensor problems), there has been good growth!

    Unfortunately my plants have been showing some nutrient deficiency problems, such as yellowing of the leaves which I remedied by adding kelp extract, and tip burn which was a result of adding too much nutrient.

    Some of the plants in the lower grow bed aren't doing so well though, and I suspect it has something to do with the water temperature (which is just room temperature, and room temperature's been very warm lately)

    Also note the addition of a hose connector - this is to allow easy disassembly, and also allows us to hook up a garden hose to drain the water.

    The hose connector has a valve in it as a fail-safe - if the pump activates while nothing is connected, the valve will block the water flow and prevent it from spraying everywhere!

    While the controller is out of action, I've been having to manually initiate pump cycles for the upper bed, typically 2x a day. I can't automate it due to the salt-buildup problem mentioned in the previous post, because it makes the water level readings completely unreliable.

    Next Steps

    • Raspberry Pi Interface & PIC/ARM controller
    • pH sensor integration (I have one verified that it works, but I need to electrically isolate it from the tank!)
    • EC sensor (need to make one. physically it's simple - just two electrodes, but need to create a circuit for it and also keep it electrically isolated)
    • New water level sensors that are resistant to salt build-up (I have an idea of how to remedy this)

  • Sensor Failure

    Jared Sanson • 04/24/2016 at 19:23 • 0 comments

    The garden pumps are activated based on water levels, which combined with timers ensures the water should never overflow or underflow. Preventing underflow is important for this ebb-and-flow design, because if the pump sucks in any air the siphon effect breaks, and the grow bed will never drain.

    Here's my current water level sensor design, basically Kapton/Mylar tape and metal foil:

    Unfortunately it looks like my water level sensor design needs rethinking - they have stopped measuring the water level properly and now behave as a boolean (ie, there either is water or there isn't).

    My current theory is that they have accumulated a layer of nutrient salt, making the whole length of the sensor slightly conductive, so it looks like the water level is higher than it really is.

    Oh well, back to the drawing board!

  • Design

    Jared Sanson • 04/05/2016 at 18:10 • 0 comments

    The garden is a two-part experiment:

    1. The upper tank is an ebb-and-flow grow bed which fills and empties on a regular schedule.
    2. The lower tank is a reservoir and aeroponics grow bed, using ultrasonic misters to create a high humidity environment for the plant roots.

    It is built with the following goals in mind:

    • Error-tolerant - If the software should ever fail, it should be impossible to cause any damage to our house (eg. flooding). This doesn't mean the plants themselves won't die from a lack of water.
    • Simple - Minimize the number of hardware parts
    • Modular - Must be able to be disassembled
    • Quiet - It is located in our living area, so it must be quiet
    • Moniterable - Equipped with lots of sensors for monitoring system health and operation.

    Error-Tolerance is achieved by using two reservoirs of the same size. If the level sensors fail and the pump keeps pumping, eventually they will run out of water and thus it is impossible to flood the room. Additionally, errors will be detected by software and the user will be alerted to any possible issues with the sensors/pumps/etc.

    Simple/Modular - It is built out of stuff you can get from the garden store or Amazon. There is only one pipe (and one pump) connecting the two reservoirs, so there is minimal plumbing.

    Quiet - The setup is almost silent due to the use of a DC brushless pump and ultrasonic mister. It's so quiet I can't even tell when it has gone through a pump cycle!

    Sensors - We need sensors to monitor system operation (water levels, water flow, humidity, etc.) and system health (pH, EC/TDS, temperature, etc.).

    Monitoring - Will be presented with a Raspberry Pi using a rich web page to show graphs of all the vital sensors. As a bonus the Raspberry Pi will capture timelapse photos of the growing process. System control is done by a separate microcontroller (Currently an Arduino Pro Mini, but I may move to something more powerful)