thebugger

modified 10 years ago

How To Grow Weed. Auto Watering v1.1

1578

12:38:00

So me and my friends have been trying to come up with a completely automised watering system for our plants and it suddenly came to me. Why invent delay circuitry which may or may not work in the scorching summer days when you can actually measure the resistance of the dry soil (the 100mohm resistors represent the electrodes and the 1.6Mohm resistor is the soil's resistance in a dry condition) and then use a Schmitt trigger's hysteresis to control the watering cycle. This is how this works. At first the soil is dry and its resistance is 1.6Mohm. That's when the trigger activates the watering system (the bulb in this case). Water starts pouring into the soil lowering its resistance. The 1.6Mohm resistance quickly falls down to 330kohm. That's the second threshold for the trigger which when reached disables the watering system. That's when the trigger enters standby mode waiting for the soil to dry off again and reach the 1.6Mohm resistance. This way even in the worst conditions (very hot summer days when the soil dries off very quickly) the precision will be infallible and the plants will always be watered at the exact time they need it.Since no more than 10uA will pass through the soil there's no danger for the plants. It just may need a once in a month or two check-up to determine the soil resistance drift from the original resistance. See as the minerals in the soil get depleted its resistance will vary slightly and if you want complete precision you must recalibrate the system. 

The thresholds are:
- Activation at 1.6Mohm
- Disabling at 330Kohm

My preliminary tests are:
- Dry soil - around 2Mohm
- Wet soil - 300kohm 

The watering system is just a fish tank pump that goes in a closed bottle with the water and one hose coming out of the bottle. As the air gets pumped in water starts coming out of the other hose. 

This is how to test it. Just lower the 1.6Mohm resistance to 330kohm as if the soil gets wattered and watch the trigger disable the watering system. It may be a few days until the soil dries off and its resistance reaches 1.6Mohm again (the second threshold)

published 11 years ago

hurz

11 years ago

Cute

MaxMinecraft107e

11 years ago

Interesting

abracadabrax

11 years ago

do u use just a simple conductor ring to measure the resistance of the soil? nice idea btw.

thebugger

11 years ago

No using a loop of conductor will shunt all the current through it and the sensing part won't work. I'd use two electrodes buried a few inches under the soil which when gotten wet will sense the changing soil resistance between them.

jewgle911

11 years ago

Just use a fuckin microcontroller

abracadabrax

11 years ago

@thebugger true dat, didn't realize this :D

hurz

11 years ago

And the plants can handel all the metallic ions molecules? DC current is probably not a good idea.

thebugger

11 years ago

The DC current can be easily attenuated to a few nA with a few clever tricks ;) a few nA are no where nearly as enough to split the water molecules or cause any toxification of the soil. Remember this is going to work with an adult plant when I build it. It won't be as fragile as you may think :)

thebugger

11 years ago

I can maybe make the current through the soil as low as 1uA maybe even lower. Just make a narrower thresholds and add a series resistor with the soil resistance. This way I'll measure a smaller voltage drop with lower current going through the soil with still a high accuracy. Just going to have to make several more measurements to tweak it just right. Or just make the electrodes with higher resistance. 1Mohm for electrodes for example totalling to 3.6Mohm. There are many ways to bypass that problem.

thebugger

11 years ago

Thanks for bringing it up by the way. It made me think about the material of the electrodes i need. Copper may erode in time so as aluminum and surely iron will rust over time and cause a faulty reading. I think im going with silver. What do you think.

Addramyrz

11 years ago

Where I work we have/use stainless steel probes that are part of the interior wall of whatever chemical container we have them in. Hooked up to a pcb that puts 19madc output. These things sit in acid or bases for a living. I believe we order them from TCD Parts.

Addramyrz

11 years ago

Used to determine the electrical conductivity of what were upto. Shouldnt be to hard to convert to automister pot-probes. ;0)

thebugger

11 years ago

Yeah stainless steel hasn't crossed my mind. It would also have the lowest toxicity deployments for the plant. Copper is not really a good choice. I'm thinking either stainless steel or silver.

Addramyrz

11 years ago

Both are excellent... The weed and the growing of it that is... Now to find a way to "stimulate" its budding with some AC pulses.

thebugger

11 years ago

I'm not really familiar with electrostimulation of the plant 🌿

faceblast

11 years ago

spray it with glass beads

faceblast

11 years ago

why don't you grow potatoes instead

thebugger

11 years ago

Why grow potatoes when you can grow weed :D my father's in the 🌾 🌽 🌻 business

thebugger

11 years ago

Just read an article about it and it turns out electrostimulation can cause severalfold growth increase and may kill some unwanted bacteria fungi and vermin in the soil. Currents up to 500mA are acceptable and I'll be using currents lower than 10uA.

Addramyrz

11 years ago

Hit that plant with some ECT! Or a fan with some strings attached to tickle the plants tummy. >;0)

Addramyrz

11 years ago

After NPR talked about a bank loan for a pot farm for 1 $400000.00 pot processing machine... I realized that I'm in the wrong field of "repairmen"

thebugger

11 years ago

I'm ,,hitting'' the plant with less than 10uA or around 2V in 2Mohm. This is neglectable in ant way considering the health of the plant. On the other hand electrostimulation has been proven to increase growth by over 50% while killing most bacteria in the soil.

Addramyrz

11 years ago

All I see when I close my eyes is a hydroponic lab with a Frankenstein-sized Jacobs ladder... Or 45 pots with a plant/ladder in each. >;0)

thebugger

11 years ago

No it's more of a small 3-4 plants (modest) setup

Addramyrz

11 years ago

Ahh.. Just a TV and the sounds of the home & garden channel should suffice then. So you can come in and be like "look! Those plants on tv grew twice as fast as you are" but it wont understand its been recorder over a few days, etc. A little emotional support "come on buddy. You can do it" and boom. A plant who's only desire is to be big and strong like those spinach plants popeye eats...

zorgrian

9 years ago

Its a great idea! I will implement something similar with an attiny85

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