Automatic Plant Care Minus The Microcontroller

Plants are a nice addition to most any habitat. Many of them bear flowers or attractive foliage, some of them help filter the air, and others, like aloe vera, have medicinal properties. While some plants require very little care, they all need a little moisture at some point. Overall, plant care is a bit fiddly: water them too much and you run the risk of root rot; water too little and risk death by dehydration. Hackaday alum [Kevin Darrah] would prefer not to gamble with either condition, and so in the course of a weekend’s time, he constructed a solar-powered automatic plant watering system from components he had on hand.

While he likely had a microcontroller or two lying around, he didn’t use one. His is a system of MOSFETs that trigger a motorized pump from one of those automatic bug spray bottles to draw from a reservoir and water the plant. The solar panel charges a bank of 6800µF capacitors that [Kevin] took out of an old receiver. When the desired charge is reached, the small soil sensor module is powered, assessing the moisture level. If the level is below the threshold determined by a trimmer pot, the power from the capacitor bank is dumped to the water pump and his plant gets a drink.

[Kevin]’s design deals nicely with the possible pitfalls of solar power. He’s included a 0.1µF cap to ensure latching through the system, and added a bleed resistor so that the pump is never powered unnecessarily. After running it for a couple of days, he’s already seeing moisture regulation in the soil. His complete demonstration and theory of operation is after the break. If you’re into solar power but aren’t quite ready to ditch the µC, check out this Arduino-controlled solution for thirsty tomatoes or this PIC-powered plant pacifier.

8 thoughts on “Automatic Plant Care Minus The Microcontroller

    1. Skipped the article to check it the first comment would mention arduino. Was not disapointed – and as a bonus you were complementary to the project and not condescending about everyones favourite microcontroller platform :) I think we found HAD_COMMENTER_2.0 in the wild!

      1. I’ve been loving the ATTiny13a. it consts about $0.50 each if you look hard enough. Unfortunately I don’t know enough about electronics to build this circuit w/o a controller.

  1. Yes, simpler indeed, quite an interesting design. It even makes sense to have solar power: more sun, more water needed.

    But since the plant is in a pot, don’t those pots with a tank underneath work better? The plant just drinks as much as it wants? Or does that lead to overweight plants?

    1. Horses for courses. Plants from arid habitats such as cacti will rot with over watering. They prefer the soil to dry out completely between downpours. Other plants, particularly fast growing shade tolerant ones, are happy being constantly moist. For a lot of fruiting plants, such as tomatoes, it’s important to avoid soil moisture fluctuations because this can spoil the fruit.

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