Archive for November 2014
Distributed Raspberry pi based Hydroponic Controller
Last couple of weeks I was building a Hydroponic system controlled by Raspberry pi. As of yesterday night my system was based on a single Raspberry pi that control one or more water pumps. It was one of my design goal to add more Pi’s based controllers to the network with zero configuration.
Why more Controllers?
As I am living in an apartment and the hydroponic system is going to be installed in the balconies. Connecting the motors installed in different balconies to a single Raspberry controller will make things ugly, I don’t want wires hanging here and there. So one option is, add another Raspberry pi controller. It’s easily doable, just install the controller software I created and plug the water pump.
As I explained in my last post, this system is controlled via mobile devices. So when ever I add a controller to my hydroponic network I have to create an entry in each of the device in which my mobile app installed. Also I have to assign a static ip to each Raspberry controller or keep track of the host name. When I start thinking about it, I see a system with some complications. Yesterday night I modified my controller application, this is what I come up with.
Unifying server and Controllers with self advertisement
I created a Unifying server in node js. The controller system running in different Raspberry pi’s advertise about it when ever it joins to my wifi network. This Unifying server will get notification whenever a new controller joins. I use Node Discovery module for service discovery and publishing. In this scenario I don’t have to worry about any configuration of the controllers. Just install my controller software in each raspberry pi and plug it into my hydroponic system.
My mobile app connects to this unifying server instead of individual controller system. All the commands to the controllers will be routed via this unifying server to respective controller. Below is the routing function I come up with.
app.use('/', router);
router.use(function (req, res, next) { options.host = req.headers.hostid; options.path = req.originalUrl; options.method = req.method; var request = http.request(options, function (response) { response.on('data', function (data) { res.setHeader('content-type', 'application/json'); res.send(data); }); }); if (req.method === 'POST') { request.setHeader('content-type', 'application/json'); request.write(JSON.stringify(req.body)); } request.end(); });
This unifying server is a very light weight system and can run in a Raspberry pi or in my computer. On of my design goal is that Controller should be self sufficient and should run in any circumstances even if there is no connection to unifying server.
The Unifying server and the Controller system is based on Node js. It’s a beautiful platform and I learned a lot about node js while building this system. Also become a huge fan of Javascript.
Next post I will go through the mobile app I created.
Happy coding…
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Hydroponics system controlled by Raspberry Pi an overview
Last couple of weeks I was spending my free time to understand and building a Hydroponic system to grow vegetables in my Apartment’s Balcony. I just don’t want to build a normal system that controlled by a timer, instead I want to build a system that I should be able to monitor even I am not at home, change watering schedule using my mobile device.
Before we jump into details, let me give you a brief about Hydroponic.
What is Hydroponics?
In simple terms, hydroponic is a system where you can grow vegetables without soil, mix the required nutrients in water and feed directly to plants. Advantage of this system is, we are feeding plants what they want, instead plant hunting for the nutrients from soil. Also less consumption of water as we reuse the water.
If you search in google you will get more details of Hydroponics. I am working on a subset of Hydroponic called Aeroponics, where plants grow vertically. I made the vertical growing tower based on the method described by Gunnar Shaffer.
Any Hydroponic system needs water circulation using a water pump, I used a submersible pump bought from Ebay for 225.00 INR. This pump should pump water in a periodical manner, say water for 15 mins then sleep for 60 mins and the cycle continues. We can use a timer to do that, it will cost from 1500 – 2500 INR. I decided to use one of the Raspberry pi lying in my table.
Why Raspberry pi?
As a programmer, this small brilliant device give me the flexibility of controlling the system with the programming language of my choice. For this system I used Node js platform to build the controller system. I spent a night to build the basic system that can turn on/off any device in a specific interval and some REST api’s through which mobile device can interact. Later I spent several nights to polish and enhancing my system.
For my testing I used a breadboard to turn off/on one LED. After I successfully controlled the LED, it’s the time to control the Electrical motor. I bought a 12v single channel Relay from ebay for 99.00 INR. It can control one electrical device, in my case the submersible water pump. This post will give you an idea about how to connect the Relay to your Raspberry pi.
Mobile Application
After I completed the system running in Raspberry pi, I decided to write the application for the mobile device. Through which I can interact with the system. As of now the application can
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Turn off the pump, in case of maintenance.
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Schedule watering interval.
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Turn on motor to water immediately.
The mobile application is written using Cordova platform, so that app can run on my Windows or Android devices.
What Next?
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Suggestion system for nutrient quantity based on the previous data.
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Distributed cluster of Pi based Aeroponics blocks controlled by a server.
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Connect Water level monitor to Rasp pi and notify if water level of the tank goes down.
Update: see my hydroponic in action.
Thanks to
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My wife, for her support and encouragement, for all the crazy stuffs that I am experimenting with.
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My father who guides and clarifies all my question related to Electrical devices and suggestions to improve the system for better performance.
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Gardenguru for providing me with key information like measuring and controlling ph and EC level. I also bought the necessary items from them like Net Cups, Hydrotons, Nutrients, etc. They have a shop near to my home, I go there and spent time talking with them. They are very enthusiastic and provide with any info about Hydroponic to a newbie like me.
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Node js error handling using modules inherited from EventEmitter
In node js most of the operations are asynchronous and normal try-catch will not work. In case of any error and we didn’t handle it properly, our node process will crash. In this post I will explain how to handle errors properly using EventEmitter.
In this e.g. we are going to read some data from a SQLite db, I use dblite as my node module to deal with SQLite db. For this e.g. I created a UserRepository module and inherited from EventEmitter
UserRepository.js
var dblite = require('dblite'); var util = require('util'); var EventEmitter = require('events').EventEmitter; var UserRepository = function () { var self = this;
self.getUser = function (userid, callback) { db.query('select * from USER where USER_ID=:id', [], { id: userId }, function (err, rows) { if (err) publishErr(err); callback(rows); }); }; var publishErr = function (err) { self.emit('error', err); }; }; util.inherits(UserRepository, EventEmitter); module.exports = UserRepository;
Using util.inherits, we inherits the UserRepository module from EventEmitter. Later we export that module to use in other node modules. The publishErr() function will emit an ‘error’ event in case of any error and calling module can subscribe to that event and handle the error.
Let’s use the above module in another node module. Say an express rest api.
restApi.js
var express = require('express'); var bodyParser = require('body-parser')
var UserRepository = require('./UserRepository'); var userRepo = new UserRepository();
var app = express(); app.use(bodyParser.json()); app.listen(8080); userRepo.on('error', function (err) { console.log(err); }); app.get('/users/;id', function (req, res) { userRepo.getUser(req.params.id, function (record) { res.send(record); }); });
Let’s go through the lines in bold.
Here we are creating the instance of UserRepository module.
var UserRepository = require('./UserRepository'); var userRepo = new UserRepository();
The calling module should subscribe for the error event, that’s what we are doing here. I am just writing the error to the console. You can do whatever you want with that err object.
userRepo.on('error', function (err) { console.log(err); });
This way we can ensure that our errors are handled properly in an elegant way.
Node js has an uncaughtException event and use it as a last resort.
process.on('uncaughtException', function (err) { console.log(err); })
+Sony Arouje
Sony Arouje 