• Initial prototype and testing

    Benjamin Blundell05/06/2018 at 20:24 0 comments

    I've used the original EMF Tilda badge before in a doorbell project. It's a really useful badge as it's essentially an Arduino with extra features. I've built a basic hydroponics setup sometime back but I've wanted to revisit it for sometime as I wanted to make quite a few improvements. For this first step, I wanted to use a computer controlled pump, connected to a battery and solar panel. I'd use small baskets, filled with the porous clay balls that form the medium, to hold the plants. These would sit in a series of pipes, with water pumped to the top, draining into the sump below, where the process starts again. The idea being that solar power alone would keep this system running.

    Greenhouse setup

    The greenhouse, complete with pump and pipework.

    The first major change is how the water is delivered. In the old setup, we used a solar pump for fountains and allowed the top half of the bed to flood and then slowly drip down. This seemed fine but there are a few problems with that. Controlling the rate is one thing. Often, the bed would flood too much and you'd loose the plants and clay balls. Secondly, having the tanks be transparent is a bad idea as algae the like can grow in it. Not only that but the roots of plants don't take too well to direct sunlight.

    I figured the best thing was to buy some PVC pipe and create a track for the water to flow down. Spaced along this track would be holes for the baskets of clay balls and plants to sit. So I bought some pipe from the local hardware store, a drill and the correct hole boring bit and set to work. All of the attachments are push-fit so it's easy to assemble.

    Drilling out the pipe for fitting the baskets.

    The greenhouse is one of these small, plastic affairs you can buy cheap from eBay or your local garden centre. It's great for when you have little space. The pipe work fits inside reasonably well, with space left over for normal plants.

    Pump it up!

    The pump was a tricky choice. I don't know anything about pumps, hydraulics and all that but I figured I'd learn. The flow rate for hydroponics is quite important. You want a certain amount of water to rush over your plants at a certain speed. If I knew more I could probably work it out, but I figured I'd start with 12V pond and fish tank style pumps. Looking at how high they can raise water seemed the obvious factor. I chose a cheap pump from eBay hoping it would work. Perhaps the harder thing was to get the fitting correct. Finding a pump with a compatible screw thread proved to be a little tricky.

    Eventually though, the line I'd bought almost fit the pump. It's not a perfect fit but it's good enough for now. Immersing the pump and linking it to the battery, I found that it actually worked! Hurray! With that hurdle overcome, it was time to take a look at the controller.


    Late night work on the EMF Badge controller and pump.

    The EMF Tilda badge has gone through a few revisions, with the most recent being quite a serious project! I've stuck with the original for now because ultimately, I want something simple that I can expand on or adapt later. Ultimately, I'll build a custom hydroponics board with all the breakouts I need. For now though, this is more than adequate.

    The circuit is fairly simple. Using a MOSFET to turn the pump on and off was quite easy. More tricky was getting the badge to run off 12V. There was some thought that the badge could do this with just a few changes to a couple of connections. I tried this but couldn't get it to work, which was a shame. In the end, I bought a 12V to 5V converter from eBay. These units are cheap enough and seem to work quite well.

    I'm still wondering how best to integrate the solar panel. Ideally, one needs to measure the voltage across both the panel and battery and decide what to do accordingly. In the end, I couldn't come up with a circuit that measures both reliably. In the end, I took the panel out of the equation and used a light sensor...

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