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Computer-based mostly-self-contained intermittent mist system

Posted by bwaynef z7 SC (My Page) on
Fri, Jun 20, 14 at 10:51

Years ago I became fascinated with the idea of propagating woody plants (trees mostly) by cuttings. Naturally the ones I was most interested in propagating are some of the most difficult; pines for instance. Intermittent mist is heralded as increasing the percentages for many species so off I went looking into setting something up. The timer, being the most important piece, was unsurprisingly the most expensive for what I wanted to be able to do: essentially have no limits as to how often or how long I could have the mist on. Accepting ANY limitations would've made the potential ready-for-purchase systems a bit more affordable, ...but I wanted to tinker. Also, I didn't want to have to tap into my plumbing, ...and would like for this to be portable if needed so I can run the propagation chamber in my greenhouse or in my garage under lights.

Here's my system:
1 Computer: I chose a Raspberry Pi ($35, memory card, case, wireless adapter closer to $60-75 ...although I had one that wasn't being used.)
1 X10 firecracker home automation set (serial dongle and switchable outlet/receiver)
1 Weed Sprayer -- or similar
1 solenoid -- or similar (plus a transformer that outputs appropriate voltage. I was able to "repurpose" one.)
Mist heads, tubing, and appropriate connectors -- Rainbird/Toro/MrDrip

I snipped the wand off the sprayer and connected that to the input side of the solenoid valve. I connected the mist/tubing stuff to the other side of the valve. Wired the solenoid to the transformer. After filling the sprayer up and pressurizing it, I plugged the transformer in and had mist.

Now, this is where I'll likely diverge from most users who follow after me. The Raspberry Pi isn't a magic bullet. Its small. Its cheap. And its powerful enough to do what I need (...and replaced 5 linear feet of computers on a shelf in the garage I was holding onto in case I wanted to do something like this. Not bad for a computer I can carry in a shirt pocket.) You can use whatever computer you have that has a serial port on it. If it doesn't have serial, you can buy a USB-serial converter (...which I should've included in the list above, since the RasPi only has USB). If your computer runs Windows, the X10-supplied software should run on it and you'll have to follow its documentation to schedule the mist.

I'm running Slackware Linux 14.1. I found a software package called "bottlerocket" that controls the x10 firecracker module and receiver. Executing bottlerocket, br, with the address of the receiver and a simple command, on or off, turns the device on or off. I created a
"br address on
sleep 10
br address off"
script. That script turns on the mist, waits 10 seconds, and turns off the mist. I called that script "mist.10" You ought to be able to extrapolate how to mist for longer and shorter than the 10 seconds I've demonstrated.

I then add a cron entry, Linux' timing/automatic-program-execution facility. Currently, I've set the mist to come on every 30 minutes for 10 seconds from 7 am through the 12pm hour. Then from 1p to 7p it comes on every 10 minutes for 10 seconds.

The crontab entry looks like this:

# Intermittent Mist
*/30 7-12 * * * /home/username/mist.10
*/10 13-19 * * * /home/username/mist.10

(Cron entries have minute, hour, day of month, month, and day of week. The asterisks tell cron to execute it regardless for that time period.)

An additional x10 receiver and a solenoid are all that's necessary to expand the system. Simply call br with the different address of the receiver and you're controlling a different "zone".

I also dabbled with a temperature/humidistat, although I never was able to get it calibrated to my liking. The temperature, at summertime daylight hours, was ~10�F higher than my wireless thermometer sitting directly above the humidistat. Also, the relative humidity read significantly lower than I believed it to be. The idea being to measure the humidity and, if it fell below a threshold, turn on the mist to increase it. Also, if the temperature was exceeded, the mist would bring it back down. That script was more complex ...and I may revisit it ...but we're going on vacation tomorrow and I needed to get this set up for several cuttings I have taken in the last week or 3. (Ginkgo seedlings cuttings *10, Trident maple *32 and Japanese Maple 'Shishigishira' *10)

For some of you, this is needlessly complex. I like to tinker and had most of these parts on-hand when it occurred to me that I could do this so it didn't cause an outlay of cash quite like buying a similarly capable timer would have.

Follow-Up Postings:

RE: Computer-based mostly-self-contained intermittent mist system

how is it working for you?
care to post a pic of the set-up?
i am collecting info as i want to set-up a sensor driven automated computer system in the future for lighting/watering mostly (misting probably too), when i have a proper space for it. not a full blown green-house style, but smth that can be set up in various tiled areas (like a sun-room/patio) and monitored over the internet, perhaps too.
smth amateurish and not too expensive. and i like to tinker.
as far as temp/humidity measurements - you need to calibrate sensors with a couple reg std devices for accuracy. the thermometer has to be in the shade and not picking up any heat from other exposed surface - any sun/exposed dark surfaces will raise the reading . and you can't really estimate humidity by feel, so don't rely on that.
was curious, whether you plugged it in other computer to configer/enter parameters.
wiki'ed it and got:
Whereas the majority of Linux systems boot into a graphical user interface, Slackware's default user environment is the textual shell / command line interface.
-- text shell would obviously be an advantage to keep it simple.
is that why you chose slackware?
so was yours outside (i see it can overheat over 85F?) or in the garage? how did you handle lighting?
what about gertboard for sensor i-face? that could be handy?
and camera/ethernet adapter, etc - the whole could be monitored/switched online. seems doable?
i foresee extensive travel in the future with remote gardening enabled set-up ;)

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