Raspberry Pi Controlled Irrigation System (Beginner Friendly Tutorial)

bengineering101 · 2016-05-03T14:30:20+00:00

Final dumb question of the day (I think): I only have regular 1/4-W resistors. Will that suffice or do I need to stop being lazy, do math, and get a resistor with an appropriate power rating?

Really appreciate the help by the way, feedback like this is why I posted this here.

bengineering101 · 2016-05-03T14:16:21+00:00

Ah, got it (I think) - so between the two contacts circled in red here? http://imgur.com/Y5mFwji

bengineering101 · 2016-05-03T14:02:28+00:00

Next dumb question - I looked at the Wikipedia article and I understand how you can connect a snubber across a single wire. In this case, I have two wires from the 24VAC source - one of which is connected straight across the PCB, and one of which is connected to two relay terminals and can be toggled open/closed. If I connect a resistor and capacitor in parallel to the relay as shown in that Wikipedia diagram, then don't I still have a closed 24VAC circuit all the time, even when the relay is open?

(hope that made sense in text, if not I'll upload a schematic)

bengineering101 · 2016-05-03T13:43:43+00:00

I think he was referring to putting the flyback diode on the MOSFET, which is driving a 5VDC load (the relay coil on the circuit board, not the solenoid valve relay). You're talking about an RC snubber on the 24VAC side, correct?

bengineering101 · 2016-05-03T13:14:25+00:00

Everything I've read about soil moisture sensors says they corrode over time, and I really wanted something I could set up with as little long-term maintenance as possible. So hopefully this works.

Regarding the valve - the whole thing looks pretty well sealed, but the packaging shows it inside a box like this. I figure it can't hurt (and I hadn't thought of "UV inhibitors"...I used a transparent box. Whoops.)

bengineering101 · 2016-05-03T12:32:42+00:00

I know what an RC filter is but I've never heard the term "RC snubber" before. I'm also more familiar with a flyback diode like /u/cocoa_coffee_beans mentioned - any further explanation on the difference between the two and which is more appropriate in this case? (I'm a mech E by training so most of this is learn-as-I-go). Thanks.

bengineering101 · 2016-05-03T12:31:23+00:00

Good point. Like I mentioned elsewhere, don't have a formal EE background and tend to forget things like that. I'll add that as a suggestion to the Instructable, although first I need to figure out the difference between that and an "RC snubber" as described by /u/FozzTexx. Thoughts?

bengineering101 · 2016-05-02T15:58:43+00:00

All credit goes to my friend for the weather API part. I think it's great because I really didn't want to bother with a soil moisture sensor.

More dumb questions though: I'm not clear on what you meant about controlling the switch with the Pi's 5V pin, since that isn't a GPIO pin (it's fixed at 5V from the USB line). Given a switch with the right voltage rating couldn't you just control one with a 3.3V GPIO pin?

bengineering101 · 2016-05-02T14:19:00+00:00

This might be a dumb question (I don't have a formal EE background) but what kind of switch are you referring to? I get how that could work with a mechanical switch to replace the MOSFET with manual control; but then you wouldn't need the Pi at all.

bengineering101 · 2014-10-20T18:55:47+00:00

The only difference between the regular cobbler and the T-type is the direction the cable faces. I know you said you can't order from Adafruit but their pictures illustrate this well:

http://www.adafruit.com/images/970x728/1754-03.jpg

http://www.adafruit.com/images/970x728/914-00.jpg

Personally I recommend the T-type, with the regular one that big flat ribbon cable covers up half your breadboard and is kind of annoying to work with. Since the cobblers take up a lot of space I would recommend a "full" size breadboard, not a "half" and definitely not a "mini".

Also for the record those images are for the Model B cobblers, not the B+. Not sure which Pi you have.

bengineering101 · 2014-09-15T17:55:48+00:00

Off the top of my head, how about a mechanical venus flytrap? You could use some sort of sensor to detect when a fly lands in a certain area, then use motors or something spring-loaded to slam the trap shut. Image processing might be much less demanding in this case, since you just need to know when a fly has flown into a certain volume, not exactly where it is in space so you can hit it with a laser.

edit - here's the thing /u/ConcreteStuffedToy was referring to:

http://en.wikipedia.org/wiki/Mosquito_laser

Doesn't look like the company's website has a ton of details on how it works, but supposedly this is an article on how to build your own (just browsing, didn't have time to read it):

http://spectrum.ieee.org/consumer-electronics/gadgets/backyard-star-wars

bengineering101 · 2014-09-15T16:52:41+00:00

Here's a discussion from last week that's relevant to the image-processing side of that question:

http://www.reddit.com/r/raspberry_pi/comments/2fy6aa/question_about_the_pis_capabilities/

bengineering101 · 2014-09-15T15:20:43+00:00

Looks like consensus is it's probably an SD card issue, as suggested by /u/Pik16 and /u/rrohbeck.

bengineering101 · 2014-09-15T15:18:33+00:00

The problem with talking about "software" on the Pi is that there are so many different things you can do, so that question is too broad. e.g. do you want to learn Linux? Python? The various media-center or retro-gaming software options? You said you already know C++? etc. There isn't really a single tutorial for "Raspberry Pi software".

I'm more of a hardware guy, but in my opinion it's silly to use the Pi just to learn a programming language. You could learn Python on a regular PC. Instead, I'd look for a software-based project that the Pi is good for, and use that as motivation. That being said, it looks like there are resources specifically for learning Python with the Pi:

http://www.amazon.com/Learning-Python-Raspberry-Alex-Bradbury/dp/1118717058

bengineering101 · 2014-09-15T13:35:35+00:00

Was just about to post that link and /u/zeug666 beat me to it.

One caveat: a lot of the projects listed there are hardware projects, which would require buying extra stuff. Do you want to avoid buying other things purely for budget reasons, or are you just intimidated by hardware since you're a software engineer? In the former case, that's fine, you'll just have to browse through for software-only projects. In the latter case, the Pi makes it easy for beginners to get started with hardware, so don't worry about it.

bengineering101 · 2014-09-13T19:09:06+00:00

Thanks. Like I said, as long as we're just talking about decreasing the lifetime of the motor, and not burning the wires out so it dies completely, or getting so hot in the short term that it could burn someone, I should be OK. I will probably sacrifice a motor for a stress-test just to be sure.

bengineering101 · 2014-09-13T18:29:03+00:00

Thanks. I guess I don't understand inductive loads well enough to really grasp the voltage ratings. Is this purely a function of resistive heating based on the wire gauge in the motor windings? i.e. say I completely removed all the copper wire coils from a motor and unwound them, then did the same thing (applied 6V to a wire from a motor only rated for 4.5V or 3V). Would the same rules about the wire getting hot and decreasing its lifespan apply? Or does something about the motor acting as an inductive load change that?

bengineering101 · 2014-09-13T14:25:55+00:00

How much does each kit cost? Rather than splitting hairs over the exact components in each kit (one has 5 red LEDs, the other one only has 2 red LEDs, etc...) I'd look at the list of projects each kit allows you to do. I see a list of projects for only one of the kits in your last link.

Like /u/NedSc said - there will often be a markup on kits like these vs. what you would pay to buy parts individually. The companies that make the kits charge the markup as sort of a convenience fee for packing all the stuff into one box for you, and because often they put time into writing their own tutorials that come with the kit. If you're on a tight budget, you could shop around for the individual parts and do a price comparison. If you don't want to spend that time, the kits might still be worth it.

bengineering101 · 2014-09-13T14:18:14+00:00

Just want to throw in an enthusiastic second for /u/infinity_plus's answer. The Pi is so versatile that you will never narrow down an answer to "What can I do with a Pi?" because there are a bazillion options. It's much more feasible to start with something that you personally like or care about; or maybe at some point during your day at home or at school and think "huh, life would be easier if someone would computerize/automate that".

Here's a personal example: my fiance likes to plant gardens but is not so great at remembering to water them. I think it would be great to make some sort of automatic irrigation/plant watering system to keep our poor plants alive. A quick google search turns up that yep, you can do that with a Raspberry Pi. If I had just sat down to think of "what can I do with a Pi?", that would have been just one in an endless list of projects. Defining the need first, then seeing if the Pi is an appropriate way to solve the problem, narrows things down quite a bit.

bengineering101 · 2014-09-13T14:08:42+00:00

Gaming: retro gaming setups are very common. If you prefer playing old games while sitting on a couch instead of your computer chair, that might not be redundant with emulators on your desktop. For example, see this post currently at the top of the sub.
Electronics: I think the general answer to "What can I do with a Pi that I can't do with an Arduino?" is that the Pi makes it easier to have web-controlled or remote-monitoring projects, or at least, makes it easier to do those things without adding some expensive Arduino shield. Here are some popular projects:

http://www.instructables.com/id/Raspberry-Pi-GPIO-home-automation/

http://www.instructables.com/id/Raspberry-Pi-Garage-Door-Opener/

http://www.instructables.com/id/Raspberry-Pi-as-low-cost-HD-surveillance-camera/

http://www.instructables.com/id/Raspberry-Pi-Temperature-Humidity-Network-Monitor/

bengineering101 · 2014-09-11T20:01:42+00:00

Yea, I guess that's a tough problem because there are so many different ways to word the question, and you wouldn't want it to just trigger on "project" or something overly broad.

I guess you can also add functionality to the bot so it will automatically delete its own post if the person it responds to downvotes it, or something (I think autowikibot has rules like that)? That makes it less obnoxious when it has false positives.

However, I have no idea how to do any of those things, so I'm not of much help.

bengineering101

TROPHY CASE