Right now, not much… but soon I hope, a set of plans and software to continuously monitor plant + pot weight during growth.
The idea is that I will combine a scale, solenoid valve and microprocessor to accurately determine when individual plants need to be fed. As a basic idea of the procedure, the cannascale will record the saturation weight of the plant + pot at every feed, and then monitor the weight of the pot as the liquid in the medium is consumed and perspired by the plant. Once the weight drops below a threshold value, the feed cycle initiates again.
For growing in coco coir, I expect this to be a superior method to simplistic time-based feeds. The risk of pots drying out will be negated, and individual plants will receive personalized attention as they need it.
As a side benefit, I should also be able to extrapolate the change in plant weight during growth. That’s a nice bit of data to have. If I can combine this with environmental monitoring (temperature & humidity), then the length of the feeding cycle should have some correlation with VPD.
For now, I’m just going to make due with parts I had laying around to build the scale. This is just a aluminum sheet I had from an old 3d printer, and some aluminum T-slot.
The weight will be measured using a piezo-based weight sensor… common elements in bathroom scales, etc. I went with a 10kg sensor. These can be sourced on ebay for a few bucks, with their respective amplifiers.
I also have some solenoid valves that will need to be switched with relays or transistors. I’m going to save that until later, and start by just monitoring the weight. Just having data to look at will help me to know the feasibility of the project, and might provide some early insights.
Next stop is to work on getting the electronics up and running…
@lefthandseeds great concept and nice thinking outside the box! It has been 10 months since you posted this, any progress or is it still in the drawing board stage?
This would be an awesome tool for someone like me that always had issues growing in soil. I could never figure out when was the best time to water and always had stunting issues because I either over watered them or let them dry out too much
Edit: I grow in coco simply cause I can set a reservoir and allow it to water everyday
Well I had a bit of a shake up and started running hydroponics instead… but I still think it would be a good idea!
Since I don’t currently have a practical use for it, I probably won’t make any progress… but winter is approaching, so maybe I’ll pick it up again. We’ll see…
cool, thanks for the update. One thing that has been wracking my brain since I read this is how do you differentiate between new growth and lack of water? It seems if it grows a gram of plant material but is down a gram of water in the soil you wouldn’t be able to tell the difference and it would be hard to calculate it’s needs based on weight for that reason, unless you were also combining it with sensors. It seems that the new growth would be an unknown and unpredictable quantity that would make it impossible to determine the amount of water in the grow medium based on weight without using moisture sensors also, though I am sure you had that factored in.
Cool idea. I’ve been following along josh_neulinger , VOP_cannabis and craft_farmer on IG/the forums and they are all using moisture sensors and software for crop steering and swear by https://www.metergroup.com/environment/products/teros-12/ And use https://aroya.io/ and hortgrow coco coir which I wish I had access to in Canada.
They crush it in coco and I definitely aspire to be at that level one day!
Yea, so what I had in mind is a sort of “high water mark” method, where you record the maximum weight immediately after watering. What I imagine is that you’ll see the weight gradually going up on a slow cadence, and on top of that you’ll see some oscillations from the medium getting dried up and the plant perspiring. Additionally, I’d have some kind of safeguard parameters like maximum time between feeding that guarantees like once per day or once per two days it will feed.
You might consider a hempy style setup and shut off on overflow. That might be a good way to regulate the amount given at feed time. Perhaps would need to increase the feeding frequency incrementally as the plant takes up more in a session. Say 10 % in volume of feed twice and cut time to next feed perhaps.
