I love these projects. They are always destined to fail from experience but are great fun anyway. I've tried a few times to do similar things. I'll catalog my disasters quickly:
1. Seedlings need blowing around a bit when they pop out or they get all spindly. Cue wiring up two 80mm PC case fans to a chain of a single astable then two monostable 555's to generate an oscillating wind field that goes on for 5 seconds each direction after a delay of 10 minutes. Dried the compost out, blew most of it it away and then killed the plants dead. No tomatoes for me!
2. Watering robot version 1. Similar to above but with a 74hc390 dividing down the clock so it only ran once every day. Used an unprotected MOSFET to control a small water pump from ebay. Back EMF blew the MOSFET up and jammed it as a short. Emptied the entire water reservoir into the pot, down the wall and into the carpet.
3. Watering robot version 2. Same as above with problems fixed. Apart from I ran out of bipolar 555's so I used CMOS ones which are a little more tetchy about noise. Cue last 555 getting jammed in an on state and the same thing happening. This time, the tupperware box with the electronics ended up getting wet and the wall wart exploded.
Edit: meant to say to the OP - nice work. This is the spirit of all things interesting :)
Fun story: we're doing a project at work to do with agriculture.
We bought some pot plants to keep alive and some cheap soil sensors; they're just two electrodes and you pass a current through the soil, measure the resistance and get a proxy for soil moisture. We left the sensor continuously logging on Friday, came back on Monday to find the plant very unhappy and the probe contacts almost completely corroded. Within a day or two it was a stump, never recovered.
Turns out you're not supposed to leave these things powered on 24/7 and capacitative sensors are a much better solution. TIL you can electrocute plants.
Seedlings need _light_ when they pop out or they get all spindly. The sun does something like 1 kW/m3, so if you're using artificial light, you will need plenty of (preferably LED/CFL) lighting.
Source: the generations of spindly tomato plants who went before the thick-stalked purple-green-leaved ones.
Why not use a relay? Less to worry about for a side project like that. If you don't need sub-millisecond switching then you gain complete isolation, constant voltage output, and AC or DC switching
But I’m a programmer, not a gardener. If I had a plant, I’d have to water it and check the plant’s health a few times per week. I decided it would be much easier if I just spent several hundred hours building a robot to do that for me. If the plant lives to be 80 years old, I come out slightly ahead.
The mark of the start of any good hobby project is a sense of humor about the time it really takes to accomplish something simple with technology on the first go-round.
So the reason your moisture sensor project failed is because those types of moisture sensors are really designed for "stick it in, test it, and pull it out" testing. If left powered on in a moist environment, the conductive material on the sensor will quickly corrode (quickly as in the span of a few hours, as is seen on the graph).
However, Vegetronix makes an ultrasonic soil moisture sensor that does not have electrodes, and thus does not corrode. It is far more complex and expensive ($40) but it's designed as a moisture sensor for sprinkler systems and as such is engineered to be left in the ground.
Edit: Link to Vegetronix sensor: http://www.vegetronix.com/Products/VH400/ . I have used it and it works well, but as it turns out, even this is not sufficient to really automate a garden. You need fertilizer. Hydroponics make dealing with that complication much easier -- until you realize that the fertilizers are caustic / acidic enough that you have to flush the lines with water as well...
In other words, there's a pretty good reason you can't buy a kit off the shelf that will grow plants :)
The sensors corrode due to oxidation caused by the DC current. It's a pretty simple design change to alternate the current flow through the sensor and prevent that oxidation by toggling the pins.
I really like the addition of the web camera - it's a nice bonus on top of the more traditional temperature/humidity/light/moisture readings that most people incorporate into these DIY systems. Much better than what I made the first time I built one of these things.[0]
The one thing that made my scratch my head was your approach to measuring moisture. There are several very reliable methods for measuring soil moisture directly (changes in resistance, capacitance, time domain reflectometry, etc) that will give you exactly what you are looking for here.
"Therefore, we felt it was fair to assume that watering based on moisture level is impossible and that GreenPiThumb is doing the best it possibly can, given certain inexorable limits of the physical world."
This just isn't true. The sensor you picked up from Sparkfun should give you decent measurements for a while before degrading gradually depending on your soil chemistry.
[0] I ran a consumer soil moisture IOT company for a few years that was sold to Scotts Miracle Gro in 2016.
Oh you may be exactly the person I need to talk to! I'm looking for a soil humidity sensor that is able to permanently sit in my garden and accurately measure soil humidity and soil temperature. Do you have any advice?
Did the pot you use have holes in the bottom? It looks like you have it just sat on a desk so I'm assuming it's basically just a bucket?
Your moisture problem could just be that you were relying too much on the water evaporating/being absorbed rather than needing to drain out. Gravel at the bottom of a pot with holes in helps water drain really well. Alternatively, without the gravel you could place the pot on a dish, fill the dish and let the water be absorbed from the bottom up.
IIRC many plants grows best in the long run if watered thoroughly and then left to dry up a bit in between.
The reason for the drying is the drying causes the roots to grow. And the reason for why it should be really soaked when watered is so that the roots will stretch towards the bottom instead of spreading out on top.
(Correct me if I'm wrong, I left farming school almost half my life ago && English is not my mother tongue.)
Yeah, it drains into a little tray underneath. I'm trying to figure out a better solution for that because we can't see how much water is in the tray, so if too much has drained out, it starts overflowing onto the table with no warning.
Also I get the sense that I shouldn't just be leaving standing water in the tray forever, but it's also pretty difficult to remove the tray and empty it.
If you are growing from seed, does the bottom up absorption still work or do you need roots first? I tried googling this but I'm reluctant to visit some of the "green" websites that dominate the results from my work computer.
Haven't had the chance to try it out in soil yet, but reading the comments it looks promising. It uses capacitance instead of resistance and connects directly to the I2C pins of the Pi. So, easier to setup and should be more reliable.
Not really made for gardening projects but its monitoring and alerting capabilities are pretty much perfect for this kind of application. Not to mention how easy it was to set it up on the Pi and get all (temperature, moisture, light) the sensor data in.
In the water distribution section the author mentions the other gardening software doesn't mention how they distribute water. There's a longer history of irrigation than there is of embedded software development, so maybe he should have talked to someone that actually does agriculture or googled 'irrigation system parts' and bought one of the thousands of existing drippers for a buck.
Of course the later heading "the gardening wasn't supposed to be hard" seems to imply that he assumes non-coding skills are easy to figure out or obvious, which is a sadly too-common trend in the tech world.
- measuring air moisture of small upside down cup on top of the soil
- measuring weight of the whole pot
Or don't measure at all and instead use precise amount of water on precise times (RTC module, medical grade piezo-electric pump). My similar project is on hold at 20 or so sketches of various types of water pumps.
I wonder if you could use the camera to detect when the plant needs water? I have a plant on my desk that I dump water into whenever it starts looking sad and it's been alive for years now.
How would measuring the weight account for the plant growing in size and weight?
You can also use a peristaltic pump for accurate watering and adding in nutrients, or adjusting pH. Sparkfun even has a kit (https://www.sparkfun.com/products/12915) for its automated bartender.
Wouldn't two temperature sensors tell a bigger difference for wet soil, as the wick temperature is lower in damp soil. If it's little difference it's probably dry.
That's at least partially how my finger works as a sensor. A finger test probably picks up sponginess too.
> Or don't measure at all and instead use precise amount of water on precise times
This may or may not work depending on location of the plant. If it's in changing temperaturs and direct sunlight, there will be periods where it needs more water.
I am so excited to see this! I've been working on a very similar project to monitor my outdoor vegetable garden using a raspberry pi and some ESP8266's. Like you, I'm using this as a project to better learn javascript, angular and django. It's in the very early stages, but I'm really loving the experience so far.
I have a enclosure (that I recently made waterproof) that sits out in my garden that has the ESP8266 wireless chip in there, which works very similar to an Arduino with built in WiFi. I have it reading data in from a soil humidity / temp sensor, an air humidity sensor, a light sensor, and a air temperature sensor.
That data gets sent back to a simple django webserver that I have running (indoors) off of a raspberry pi. It records all the sensor readings every 10 minutes and registers them to various plots in my garden. And then, if there are any big issues (no light for 2 days, lower than average soil humidity or soil temperature, etc), it texts me.
Eventually I'll connect it to my irrigation system, but I don't trust it enough yet!
I have the exact same problem with soil humidity sensors that you mentioned. I even sprung for some fancy ones (http://bit.ly/2sMNRnD) that claim to be waterproof. I cannot make them read useful information and, once it rains or I water outdoors, the sensors read 99% for the next few days. It's very frustrating and the missing piece to make all of this work.
Like you, this started as a quick, month-long project and now it's become something a lot bigger :)
I think eventually I'd like to build this out to be a vegetable garden planner, so I can plan my vegetable garden at the start of the season, monitor what's happening with them, and automatically trigger my irrigation system if needed.
Anyway - it was great to read this! I'd love to hear how this project evolves and would be happy to share any of my experiences as I've put this together.
P.S. And, it's a long shot, but if you (or anyone is reading this) figures how to accurately measure soil humidity temperature in a waterproof environment, I would be forever grateful!
Soil moisture measurements can be scientific if you have enough money. Look up Time Domain Reflectometry and Soil Moisture Tension.
I don't understand TDR well enough to explain it, so I will let you search for your own info. The cheapest usable TDR sensor is about $350.
Tension has a simple analogy; a Slurpee (is that trademarked?) is easy to drink through a straw in the beginning, but it gets harder to pull the liquid up the straw as you drink more of it. That's tension and plants also struggle to pull the water from the soil depending on lots of factors including the composition of the soil, the amount of water present, drainage, etc.
There are several sensors that can be used to measure tension but none are accurate in all conditions, so people who want to measure tension tend to use multiple sensors of different types and triangulate on a useful number.
Large scale farming (in dirt across thousands of acres) is where the complex sensors are needed because the soil attributes are not uniform.
When you're gardening in a pot indoors or in a greenhouse with the same soil everywhere (because you bought bags of it), you can use those $0.43 resistance probes and just calibrate your watering amounts and intervals over time. Pump on for X units of time, ignore for Y units to let the water move through the soil, then sample every Z units until it needs more.
Love this. I went down a similar path last year, using a Raspberry Pi to water an outdoor vegetable patch. In the end I used a package [1] to control a remote controlled plug socket. I also hit similar problems with soil moisture, so went down the route of pulling a weather feed - pump water if it isn't going rain. Easy if you are watering outside!
A raspberry pi is the wrong choice for this project from my perspective, complexity is far too high for a simple project. I looked at building the same thing (minus watering) because it seemed commercial products were way too expensive (Parrot Flower Power is $60!).
The cheapest DIY solution I could think of was ESP8266 ($2), Vreg ($.5), moisture sensor ($.5) and LiPo battery (i have many of these..) but I decided I didn't have time or inclination to write the software.
Hmm. A MOSFET for a motor switch might be overkill. Also, there's no flyback diode. So your Pi pretty much will let its blue smoke out when you get a flyback voltage, or at least the MOSFET.
As for the faulty soil moisture, check out tropf blumat. It's made in Germany (you know the Germans make good stuff). It uses osmosis and gravity to keep the soil moisture consistent, no electricity. I've had great success with roots even growing up out of the soil towards the drippers https://youtu.be/UWPLr0Selh8
So great to read. This is exactly the kind of project the Raspberry Pi was designed to enable - doing something a bit odd (and arguably pointless!) but having fun and learning loads along the way.
The plants look waterlogged; the roots need air to breathe.
Drain the water back into the reservoir (use a simple filter to prevent damage to the pump) and just use a schedule for watering.
I used a mechanical timer switch for 15 mins every hour for my hyrdo setup. For soil, such tiny plants, and no lights you would need far less frequency. A general rule of thumb is to give it enough time between waterings to let it get a bit dry.
I also thought about doing a project like that, thanks for the write-up. I somehow can't really believe that it's that hard to measure soil moistures.
Are there any industrial plant moisturing robots? What approaches do these use?
Edit: I met this guy a few months ago at a faire: https://lambdanodes.wordpress.com/ The project doesn't seem to have advanced since then, but maybe he'll get better results with his epsilon node.
I'm not much of a gardener but the idea of measuring the moisture level seems ill-conceived... Namely because you are measuring at only a single point in your 3D region of soil, and you don't know what range of moisture should be maintained without experimentation.
Using our guy's own sawtooth model of watering/drainage, it would make more sense to just water at fixed intervals and experiment with the frequency to see if the plant grows.
As the plant grows the rate of water being removed from the soil increases, so the amount of water supplied will need to increase. Varience in illumination, temp, and humidity will also change transpiration rates.
I have a pretty similar project. But the problem with the mainstream moisture sensors is that they break after some time (or I did not find a good one). For myself I found the expensive solution a flower power from parrot http://global.parrot.com/au/products/flower-power/ a handy solution. It workes with bluetooth and they have some documentation. I did some working for python: https://github.com/Dlotan/flower-master-fab/blob/master/app/... and get good results over a long perioud without too many outliers
As a city dweller who has grown a lot of plants on balconies and in apartments I have also been down that road but I found a much easier solution to the watering. Autopots[1].
With those you can have 6 plants on a single 47l tank and only re-fill it every month. (depends on how thirsty they are)
It's a gods send when I want to go away for a few weeks vacation.
For other house plants that are not connected to a huge water tank I tend to just turn over a 2l plastic bottle into the soil after thoroughly saturating it first with water.
So with this the only real requirement I had for my grow op was monitoring. Because I have hard wood floors and I don't want them to swell up due to a leaking tank.
For those who don't want to / can't pay for it (eg the developing world), burying unglazed pots will also work. It's probably the most water-efficient method in arid land. The technique is at least 4000 years old.
[+] [-] setq|8 years ago|reply
1. Seedlings need blowing around a bit when they pop out or they get all spindly. Cue wiring up two 80mm PC case fans to a chain of a single astable then two monostable 555's to generate an oscillating wind field that goes on for 5 seconds each direction after a delay of 10 minutes. Dried the compost out, blew most of it it away and then killed the plants dead. No tomatoes for me!
2. Watering robot version 1. Similar to above but with a 74hc390 dividing down the clock so it only ran once every day. Used an unprotected MOSFET to control a small water pump from ebay. Back EMF blew the MOSFET up and jammed it as a short. Emptied the entire water reservoir into the pot, down the wall and into the carpet.
3. Watering robot version 2. Same as above with problems fixed. Apart from I ran out of bipolar 555's so I used CMOS ones which are a little more tetchy about noise. Cue last 555 getting jammed in an on state and the same thing happening. This time, the tupperware box with the electronics ended up getting wet and the wall wart exploded.
Edit: meant to say to the OP - nice work. This is the spirit of all things interesting :)
[+] [-] joshvm|8 years ago|reply
We bought some pot plants to keep alive and some cheap soil sensors; they're just two electrodes and you pass a current through the soil, measure the resistance and get a proxy for soil moisture. We left the sensor continuously logging on Friday, came back on Monday to find the plant very unhappy and the probe contacts almost completely corroded. Within a day or two it was a stump, never recovered.
Turns out you're not supposed to leave these things powered on 24/7 and capacitative sensors are a much better solution. TIL you can electrocute plants.
[+] [-] trevos|8 years ago|reply
[+] [-] danesparza|8 years ago|reply
What a lovely way to learn about the world ... by taking copious notes about all of the (surprising) things that don't work.
[+] [-] zild3d|8 years ago|reply
[+] [-] brightball|8 years ago|reply
Looks like a cool project.
[+] [-] crusso|8 years ago|reply
The mark of the start of any good hobby project is a sense of humor about the time it really takes to accomplish something simple with technology on the first go-round.
[+] [-] F_J_H|8 years ago|reply
[+] [-] exelius|8 years ago|reply
However, Vegetronix makes an ultrasonic soil moisture sensor that does not have electrodes, and thus does not corrode. It is far more complex and expensive ($40) but it's designed as a moisture sensor for sprinkler systems and as such is engineered to be left in the ground.
Edit: Link to Vegetronix sensor: http://www.vegetronix.com/Products/VH400/ . I have used it and it works well, but as it turns out, even this is not sufficient to really automate a garden. You need fertilizer. Hydroponics make dealing with that complication much easier -- until you realize that the fertilizers are caustic / acidic enough that you have to flush the lines with water as well...
In other words, there's a pretty good reason you can't buy a kit off the shelf that will grow plants :)
[+] [-] atourgates|8 years ago|reply
Actually - I've had great luck with an AeroGarden. A friend got me their Harvest Touch model in the fall, and I successfully grew herbs all winter.
Then this spring I started tomato seedlings in it, and had far-and-away the most successful tomato seedling starts in my decade of trying.
My model is the Harvest Touch - which tells you when to add water and fertilizer on a screen. But there are more advanced models that connect via WiFi: http://www.aerogarden.com/aerogardens/wi-fi-aerogardens/mira...
I don't see much value in the "smart" features, but as far as easy-indoor hydroponics, they really can't be beat.
[+] [-] HeyLaughingBoy|8 years ago|reply
[+] [-] mtlynch|8 years ago|reply
[+] [-] Eduardo3rd|8 years ago|reply
The one thing that made my scratch my head was your approach to measuring moisture. There are several very reliable methods for measuring soil moisture directly (changes in resistance, capacitance, time domain reflectometry, etc) that will give you exactly what you are looking for here.
"Therefore, we felt it was fair to assume that watering based on moisture level is impossible and that GreenPiThumb is doing the best it possibly can, given certain inexorable limits of the physical world."
This just isn't true. The sensor you picked up from Sparkfun should give you decent measurements for a while before degrading gradually depending on your soil chemistry.
[0] I ran a consumer soil moisture IOT company for a few years that was sold to Scotts Miracle Gro in 2016.
[+] [-] nrs26|8 years ago|reply
Currently I'm using this one: https://www.adafruit.com/product/1298
But after 3-4 waterings, it reads 95-100% consistently, regardless of the temperature. I've tried 2 of their sensors and have had the same problem.
[+] [-] dethswatch|8 years ago|reply
Can you point us in the right direction on this? The wiki doesn't make it clear how it would be used for measuring soil moisture.
[+] [-] danhardman|8 years ago|reply
Your moisture problem could just be that you were relying too much on the water evaporating/being absorbed rather than needing to drain out. Gravel at the bottom of a pot with holes in helps water drain really well. Alternatively, without the gravel you could place the pot on a dish, fill the dish and let the water be absorbed from the bottom up.
[+] [-] reitanqild|8 years ago|reply
Alittle more details about watering:
IIRC many plants grows best in the long run if watered thoroughly and then left to dry up a bit in between.
The reason for the drying is the drying causes the roots to grow. And the reason for why it should be really soaked when watered is so that the roots will stretch towards the bottom instead of spreading out on top.
(Correct me if I'm wrong, I left farming school almost half my life ago && English is not my mother tongue.)
[+] [-] mtlynch|8 years ago|reply
Also I get the sense that I shouldn't just be leaving standing water in the tray forever, but it's also pretty difficult to remove the tray and empty it.
[+] [-] kingosticks|8 years ago|reply
[+] [-] 2III7|8 years ago|reply
https://www.tindie.com/products/miceuz/i2c-soil-moisture-sen...
Haven't had the chance to try it out in soil yet, but reading the comments it looks promising. It uses capacitance instead of resistance and connects directly to the I2C pins of the Pi. So, easier to setup and should be more reliable.
On the software side I use Grafana https://grafana.com/
Not really made for gardening projects but its monitoring and alerting capabilities are pretty much perfect for this kind of application. Not to mention how easy it was to set it up on the Pi and get all (temperature, moisture, light) the sensor data in.
[+] [-] 05|8 years ago|reply
http://playground.arduino.cc/Main/CapacitiveSensor
[+] [-] thedaniel|8 years ago|reply
Of course the later heading "the gardening wasn't supposed to be hard" seems to imply that he assumes non-coding skills are easy to figure out or obvious, which is a sadly too-common trend in the tech world.
[+] [-] bfu|8 years ago|reply
[+] [-] rwmj|8 years ago|reply
[+] [-] criddell|8 years ago|reply
[+] [-] cbanek|8 years ago|reply
You can also use a peristaltic pump for accurate watering and adding in nutrients, or adjusting pH. Sparkfun even has a kit (https://www.sparkfun.com/products/12915) for its automated bartender.
[+] [-] kpil|8 years ago|reply
That's at least partially how my finger works as a sensor. A finger test probably picks up sponginess too.
[+] [-] hvidgaard|8 years ago|reply
This may or may not work depending on location of the plant. If it's in changing temperaturs and direct sunlight, there will be periods where it needs more water.
[+] [-] nrs26|8 years ago|reply
Here's a picture of my setup. http://imgur.com/a/BV188
I have a enclosure (that I recently made waterproof) that sits out in my garden that has the ESP8266 wireless chip in there, which works very similar to an Arduino with built in WiFi. I have it reading data in from a soil humidity / temp sensor, an air humidity sensor, a light sensor, and a air temperature sensor.
That data gets sent back to a simple django webserver that I have running (indoors) off of a raspberry pi. It records all the sensor readings every 10 minutes and registers them to various plots in my garden. And then, if there are any big issues (no light for 2 days, lower than average soil humidity or soil temperature, etc), it texts me.
Eventually I'll connect it to my irrigation system, but I don't trust it enough yet!
I have the exact same problem with soil humidity sensors that you mentioned. I even sprung for some fancy ones (http://bit.ly/2sMNRnD) that claim to be waterproof. I cannot make them read useful information and, once it rains or I water outdoors, the sensors read 99% for the next few days. It's very frustrating and the missing piece to make all of this work.
Like you, this started as a quick, month-long project and now it's become something a lot bigger :)
I think eventually I'd like to build this out to be a vegetable garden planner, so I can plan my vegetable garden at the start of the season, monitor what's happening with them, and automatically trigger my irrigation system if needed.
Anyway - it was great to read this! I'd love to hear how this project evolves and would be happy to share any of my experiences as I've put this together.
P.S. And, it's a long shot, but if you (or anyone is reading this) figures how to accurately measure soil humidity temperature in a waterproof environment, I would be forever grateful!
[+] [-] faster|8 years ago|reply
I don't understand TDR well enough to explain it, so I will let you search for your own info. The cheapest usable TDR sensor is about $350.
Tension has a simple analogy; a Slurpee (is that trademarked?) is easy to drink through a straw in the beginning, but it gets harder to pull the liquid up the straw as you drink more of it. That's tension and plants also struggle to pull the water from the soil depending on lots of factors including the composition of the soil, the amount of water present, drainage, etc.
There are several sensors that can be used to measure tension but none are accurate in all conditions, so people who want to measure tension tend to use multiple sensors of different types and triangulate on a useful number.
Large scale farming (in dirt across thousands of acres) is where the complex sensors are needed because the soil attributes are not uniform.
When you're gardening in a pot indoors or in a greenhouse with the same soil everywhere (because you bought bags of it), you can use those $0.43 resistance probes and just calibrate your watering amounts and intervals over time. Pump on for X units of time, ignore for Y units to let the water move through the soil, then sample every Z units until it needs more.
[+] [-] mtlynch|8 years ago|reply
Your project looks really cool! Is your code open source? I'd love to check it out.
[+] [-] jbeales|8 years ago|reply
[+] [-] zfunk|8 years ago|reply
[1] https://github.com/dmcg/raspberry-strogonanoff
[+] [-] mtlynch|8 years ago|reply
[+] [-] grw_|8 years ago|reply
The cheapest DIY solution I could think of was ESP8266 ($2), Vreg ($.5), moisture sensor ($.5) and LiPo battery (i have many of these..) but I decided I didn't have time or inclination to write the software.
I continued looking for commercial products, and ordered one of these: https://www.aliexpress.com/item/Chinese-Version-Original-Xia...
Pros- Cheap ($15). Has temperature, light and 'fertility' (capacitance?) sensor. Cons- Logs to phone app (in chinese) via BTLE instead of WiFi.
After a few weeks it seems to be working satisfactorily and I will probably order a few more units.
[+] [-] urethrafranklin|8 years ago|reply
Not that there's anything wrong with building your own device. Just don't lie about it.
[+] [-] kingosticks|8 years ago|reply
[+] [-] lloydjatkinson|8 years ago|reply
[+] [-] joshribakoff|8 years ago|reply
[+] [-] mtlynch|8 years ago|reply
[+] [-] jnty|8 years ago|reply
[+] [-] tp3z4u|8 years ago|reply
Drain the water back into the reservoir (use a simple filter to prevent damage to the pump) and just use a schedule for watering.
I used a mechanical timer switch for 15 mins every hour for my hyrdo setup. For soil, such tiny plants, and no lights you would need far less frequency. A general rule of thumb is to give it enough time between waterings to let it get a bit dry.
[+] [-] hammock|8 years ago|reply
Quite an advanced bot: as close to a human as you can get!
[+] [-] dbrgn|8 years ago|reply
Are there any industrial plant moisturing robots? What approaches do these use?
Edit: I met this guy a few months ago at a faire: https://lambdanodes.wordpress.com/ The project doesn't seem to have advanced since then, but maybe he'll get better results with his epsilon node.
[+] [-] schiffern|8 years ago|reply
Sure there are. They look like this: https://upload.wikimedia.org/wikipedia/commons/8/86/PivotWit...
I assume you mean the second/third definition of "robot," since GreenPiThumb doesn't look like a human. https://www.merriam-webster.com/dictionary/robot
[+] [-] ldp01|8 years ago|reply
Using our guy's own sawtooth model of watering/drainage, it would make more sense to just water at fixed intervals and experiment with the frequency to see if the plant grows.
Still a fun project!
[+] [-] thatcat|8 years ago|reply
[+] [-] Dlotan|8 years ago|reply
[+] [-] INTPenis|8 years ago|reply
With those you can have 6 plants on a single 47l tank and only re-fill it every month. (depends on how thirsty they are)
It's a gods send when I want to go away for a few weeks vacation.
For other house plants that are not connected to a huge water tank I tend to just turn over a 2l plastic bottle into the soil after thoroughly saturating it first with water.
So with this the only real requirement I had for my grow op was monitoring. Because I have hard wood floors and I don't want them to swell up due to a leaking tank.
1. https://autopot.co.uk/products/
[+] [-] schiffern|8 years ago|reply
For those who don't want to / can't pay for it (eg the developing world), burying unglazed pots will also work. It's probably the most water-efficient method in arid land. The technique is at least 4000 years old.
https://www.treehugger.com/green-food/unglazed-clay-pots-cre...