Moisture Meter for Plants
My wife suggested to me the idea of a visual indication for the soil moisture level in a houseplant (that is, before the brown leaves indication). We hadn’t seen anything like it in stores. So I made a prototype which worked quite nicely, and then we found that they were already available online through retailers like Amazon. Here’s the prototype I made:
It has two probes at one end that get inserted into the soil, and the LED then flashes either red, yellow, or green depending on the moisture content of the soil. It all runs on one AAA battery for about a month, but that could be improved by reducing the flash time and ADC sampling. The code for the prototype flashes the LED every second or two and samples every time.
8 Comments to Moisture Meter for Plants
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This seems like an interesting concept, do you have an explanation on the method used to measure the moisture content? What about the circuit/programs you developed?
I just used the fact that the soil will have some varying amount of conductivity based on the level of moisture in the system. Dry soil won’t conduct electricity, but wet soil will because of the high levels of impurities dissolved in the water by the soil. The circuit I made just checks the amount of conductivity of the soil at some interval, and then flashes an appropriate color LED.
How about you publish PCB files and schematics?
A possible better approach, would be to use a solar powered Cell, together with some kind of battery/accumulator (Capacitor ?) and then have a push button to trigger the test !
This way, no AAA batteries are required, and it still is simple to use.
Are you using ferrite rods, to stick into the soil ?
Hey, I like that. That would work really well. I didn’t think of putting a button on it to “check soil”, but using that approach you could omit the batteries completely. I may have to start playing with the new supercapacitors, as you suggested it would be perfect for this application.
The probes were just some small copper tubing that I tinned and then put heat shrink on.
Hi there, can you, please, supply the schematic diagram for this very interesting project?
thanks
Hi,
I can’t see what step-up regulator you are using in this project. Can you share the schematics with us? I am working on an “automatic blinds” and don’t have much room for the batteries there, so this booster IC would be just perfect for me!
Regards!
The step-up converter is TI’s TPS61221. It’s incredibly small at 2mm x 2mm, SC-70 6-pin package. I made the PCB on my CNC, but it was really at my machine’s limits.
It worked well, and seems pretty efficient at the load I was using (the AVR). You may want to select a different part depending on your load to get better efficiency. The curves for efficiency vs. current draw are given in the datasheet. They have a few different parts to match high efficiency with current draw.
I used the reference design from TI’s datasheet to make the schematic. There’s even a recommended layout. http://focus.ti.com/lit/ds/symlink/tps61221.pdf