Sony Arouje

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Archive for the ‘Raspberry Pi’ Category

RF Communication using nrf24L01 and Nodejs addon

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Recently I started experimenting with radio communication with low cost nrf24L01 modules. These modules are very cheap compare to XBee modules which I used earlier. With these nrf24 modules we could enable wireless communication between Arduinos and Raspberry pi very effectively and economically. For my experiment I used two nrf24 modules, one connected to an Arduino Uno and another to a Raspberry pi 1.  Here is the pin connection details

Seq NRF24L01 RPi Arduino Uno
1 GND 25 (GND) GND
2 VCC 17 (3.3v) 3.3v
3 CE 15 7
4 CSN 24 8
5 SCK 23 13
6 MOSI 19 11
7 MISO 21 12


For testing the communication, I used the RF24Network library, which is very good and has good documentation. Also it comes with e.g for both Arduino and RPi. So I didn’t write any single code just used the e.g and able to see the communication working, initially I had some troubles and at the end every thing worked well, I can see the data coming from Arduino in RPi. 

My intention is to use these modules in RPi and write code in nodejs. Unfortunately there is no nodejs support for this library. So last night I decided to write a nodejs addon for this C/C++ library. I didn’t had any experience in writing a nodejs addon, I spend an hour understanding the Nan and creating very simple addons. Then I started writing the addon for RF24Network, this task was very hard than trying with simple hello world addons.

Node-gyp was keep on failing when it tries to compile the RFNetwork modules. In my searches I realized that node-gyp uses make utility and I need to add the C/C++ files of this library. At the end I could compile the node addon. See the binding.gyp file

{ "targets": [ { "target_name": "nrf24Node", "sources": [ "", "RF24/RF24.cpp", "RF24/utility/RPi/spi.cpp", "RF24/utility/RPi/bcm2835.c", "RF24/utility/RPi/interrupt.cpp", "RF24Network/RF24Network.cpp", "RF24Network/Sync.cpp" ], "include_dirs": [ "<!(node -e \"require('nan')\")", "RF24Network", "RF24" ], "link_settings": { "libraries": [ "-RF24", "-RFNetwork" ] } } ] }


I should say, I am just a beginner in node-gyp and this binding.gyp might need some improvements. Anyway with this gyp file, the compilation succeeded.

Next is to create the addon file. Here I had to learn more about the data types of Nan and Callbacks. I started simple functions to begin with and compile again, then moved on to next. I took more time in understanding callbacks which allows the addon to call javascript callback functions. Also spend a lot of time in understanding threading and creating a module to continuous listening of incoming messages and trigger the callback function, so that nodejs can process those incoming messages. I use libuv for threading, it seems more easy to understand than Async worker modules in Nan.

That whole night I spend learning and writing and refactoring the addon, I finished the module by early morning. By that time I could write a nodejs app and could listen to incoming messages.

Here is the sample code in node js to listen and acknowledge the message back to the sender.

var rf24 = require('./build/Release/nrf24Node.node'); rf24.begin(90,00); rf24.printDetails(); rf24.write(1,"Ack"); rf24.readAsync(function(from, data){ console.log(from); console.log(data); rf24.write(from,"Ack"); }); process.on('SIGINT', exitHandler); function exitHandler() { process.exit(); rf24.close(); }


Here is the complete addon. The code is uploaded to github, with the steps to compile and use it your own nodejs applications.

#include <nan.h> #include <v8.h> #include <RF24.h> #include <RF24Network.h> #include <iostream> #include <ctime> #include <stdio.h> #include <time.h> #include <string> using namespace Nan; using namespace v8; RF24 radio(RPI_V2_GPIO_P1_15, BCM2835_SPI_CS0, BCM2835_SPI_SPEED_8MHZ); RF24Network network(radio); Nan::Callback *cbPeriodic; uv_async_t* async; struct payload_t { // Structure of our payload char msg[24]; }; struct payload_pi { uint16_t fromNode; char msg[24]; }; //-------------------------------------------------------------------------- //Below functions are just replica of RF24Network functions. //No need to use these functions in you app. NAN_METHOD(BeginRadio) { radio.begin(); } NAN_METHOD(BeginNetwork){ uint16_t channel = info[0]->Uint32Value(); uint16_t thisNode = info[0]->Uint32Value(); network.begin(channel,thisNode); } NAN_METHOD(Update) { network.update(); } NAN_METHOD(Available) { v8::Local<v8::Boolean> status = Nan::New(network.available()); info.GetReturnValue().Set(status); } NAN_METHOD(Read) { payload_t payload; RF24NetworkHeader header;,&payload,sizeof(payload)); info.GetReturnValue().Set(Nan::New(payload.msg).ToLocalChecked()); } //-------------------------------------------------------------------------------- NAN_METHOD(Begin){ if (info.Length() < 2) return Nan::ThrowTypeError("Should pass Channel and Node id"); uint16_t channel = info[0]->Uint32Value(); uint16_t thisNode = info[1]->Uint32Value(); radio.begin(); delay(5); network.begin(channel, thisNode); } NAN_METHOD(Write){ if (info.Length() < 2) return Nan::ThrowTypeError("Should pass Receiver Node Id and Message"); uint16_t otherNode = info[0]->Uint32Value(); v8::String::Utf8Value message(info[1]->ToString()); std::string msg = std::string(*message); payload_t payload; strncpy(payload.msg, msg.c_str(),24); RF24NetworkHeader header(otherNode); bool ok = network.write(header,&payload, sizeof(payload)); info.GetReturnValue().Set(ok); } void keepListen(void *arg) { while(1) { network.update(); while (network.available()) { RF24NetworkHeader header; payload_t payload;,&payload,sizeof(payload)); payload_pi localPayload; localPayload.fromNode = header.from_node; strncpy(localPayload.msg, payload.msg, 24); async->data = (void *) &localPayload; uv_async_send(async); } delay(2000); } } void doCallback(uv_async_t *handle){ payload_pi* p = (struct payload_pi*)handle->data; v8::Handle<v8::Value> argv[2] = { Nan::New(p->fromNode), Nan::New(p->msg).ToLocalChecked() }; cbPeriodic->Call(2, argv); } NAN_METHOD(ReadAsync){ if (info.Length() <= 0) return Nan::ThrowTypeError("Should pass a callback function"); if (info.Length() > 0 && !info[0]->IsFunction()) return Nan::ThrowTypeError("Provided callback must be a function"); cbPeriodic = new Nan::Callback(info[0].As<Function>()); async = (uv_async_t*)malloc(sizeof(uv_async_t)); uv_async_init(uv_default_loop(), async, doCallback); uv_thread_t id; uv_thread_create(&id, keepListen, NULL); uv_run(uv_default_loop(), UV_RUN_DEFAULT); } NAN_METHOD(PrintDetails) { radio.printDetails(); } NAN_METHOD(Close){ uv_close((uv_handle_t*) &async, NULL); } NAN_MODULE_INIT(Init){ Nan::Set(target, New<String>("beginRadio").ToLocalChecked(), GetFunction(New<FunctionTemplate>(BeginRadio)).ToLocalChecked()); Nan::Set(target, New<String>("beginNetwork").ToLocalChecked(), GetFunction(New<FunctionTemplate>(BeginNetwork)).ToLocalChecked()); Nan::Set(target, New<String>("update").ToLocalChecked(), GetFunction(New<FunctionTemplate>(Update)).ToLocalChecked()); Nan::Set(target, New<String>("printDetails").ToLocalChecked(), GetFunction(New<FunctionTemplate>(PrintDetails)).ToLocalChecked()); Nan::Set(target, New<String>("available").ToLocalChecked(), GetFunction(New<FunctionTemplate>(Available)).ToLocalChecked()); Nan::Set(target, New<String>("read").ToLocalChecked(), GetFunction(New<FunctionTemplate>(Read)).ToLocalChecked()); Nan::Set(target, New<String>("readAsync").ToLocalChecked(), GetFunction(New<FunctionTemplate>(ReadAsync)).ToLocalChecked()); Nan::Set(target, New<String>("write").ToLocalChecked(), GetFunction(New<FunctionTemplate>(Write)).ToLocalChecked()); Nan::Set(target, New<String>("close").ToLocalChecked(), GetFunction(New<FunctionTemplate>(Close)).ToLocalChecked()); Nan::Set(target, New<String>("begin").ToLocalChecked(), GetFunction(New<FunctionTemplate>(Begin)).ToLocalChecked()); } NODE_MODULE(nrf24Node, Init)

All the credit goes to the developers of RF24 and RF24Network library, I just created an addon for the great library. Along the way I learned a lot and could finish the nodejs addon.


Happy coding…

Written by Sony Arouje

February 5, 2017 at 4:57 pm

Farm Automation system based on Arduino and Raspberrypi

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Last two weeks, in my free time, I was working on a system to automate  Green house or an open field. The system designed using Arduino Nano and Raspberry Pi. The Arduino is used to read sensors and control devices and the Raspberry pi is the brain that decides what to do when an event detected by Arduino. All the systems communicates wirelessly via XBee.

In normal scenario in a farm we have to

  • Switch on the drip irrigation pump when the soil humidity is low.
  • Switch off when the soil is wet.
  • Switch on the Main motor that connects to a water source when the reservoir level goes down.
  • Switch off the main motor when the reservoir is full.
  • If it’s a Green house then monitor the humidity and control devices to increase or decrease the humidity. Also need to control temperature.


Below is a very ugly drawing I could come up : ), to explain the system.



Arduino based nodes

The nodes are connected to different Sensors like Soil Humidity, Temperature, Air Humidity, etc. Also the nodes can also switch on/Off drip irrigation motor, switch on/off Reservoir’s Solenoid valves, or control any hardware needed in the field.

Raspberry pi Brain

I developed this central/brain system in Nodejs. The system is very much generic and run based on configurations. So nothing is hardcoded. The XBee connected to the pi act as the coordinator and receive periodic sensor inputs from Ardunio connected in the field. This system can issue command to control devices based on the sensor inputs.


Let’s go through some of the scenarios to see how the system works.

Watering the plants: From the above picture you can see, there are 5 Arduino’s in the field sensing different parameters. For now lets think that they all reads the soil humidity. Say soil humidity value range from 0 to 100, where 0 is dry and 100 is fully wet. We need to switch on the drip irrigation motor when any of the sensor value is less than 20. Once all the sensor give a humidity value greater than 90 we need to switch off the motor.

As you can see the system need to take action based on the values coming from the sensor. Depending upon the crops these values can be changed. That’s where the Central Node js system comes into play.

In the central system, we can group the Sensor nodes and configure the triggering points. Also we can configure what to do when the triggering points reach. For e.g. in the above case we can say when the soil humidity of any sensor goes below 20, then send the Motor switch on command to the node sitting next to the Reservoir motor. To switch off the motor, the system needs approval from all the sensors, that means the motor will get switched off if all the nodes reported value is greater than 90.

Failover: What happens when a sensor node dies without sending soil humidity greater than 90 value, will the motor run whole day? No, the central system can be configured for that too, while configuring we can set up a timeout period. If the central system is not receiving high water level after a configured time, it automatically sends a Switch off command to the desired Arduino node to switch off the motor.

Filling Reservoir: From the above diagram, we can see there are two reservoirs and one Main motor. The main motor need to switch on to fill the Reservoir. Each reservoir is equipped with sensors to detect the High and Low water level. Also each water input is equipped with a solenoid valve. If the reservoir is high then the solenoid valve will close the input thus protect the reservoir from overflowing. Once all the reservoir get filled the system will switch off the Main motor before closing the last solenoid, other wise the pressure increase and can damage the Main motor.

The Arduino node will send a Water low when the water go down below a desired level. Then the central system will open the Solenoid before switching on the Main motor. The valve will open only for the reservoir where the water is low, rest all the valves will be closed.

If more than one Reservoir’s water is low then those valves will be open and the main pump will work until all the reservoir’s are filled. For e.g. say Reservoir A and B’s water level is low then both the valves will be open and switch on the main pump. A get filled and B is still not full then A’s valve will get closed. Once B is full the system will send Main pump switch off command then sends the command to close B’s valve.


System design

All the above scenarios are based on certain rules and all these rules are configurable. The central system is not aware of any rules. Based on the fields condition we need to configure it.


User can also see the activities in the farm via a dashboard. I haven’t designed any Dashboard UI yet.


Happy farming…

Written by Sony Arouje

February 17, 2016 at 6:16 pm

Communication between Raspberry Pi and Arduino using XBee

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Recently I was doing some experiments to establish a wireless communication between a Raspberry pi and Arduino. To establish wireless communication I used XBee Pro Series 2 from Digi International. The idea behind this test setup is to test, whether I can control devices like motor or read different sensors remotely.

One of the biggest advantage of using XBee is, you can find a lot of tutorials and libraries for any kind of system and programming languages. For this test app, I used Node js in RPi and C in Arduino.

Test Setup

XBee: I configured two xbee, one as Coordinator and another as Router. Both in API mode 2 (AP =2). I used XCTU to configure both the device. Only reason to choose API 2 is because the Arduino library I used only support API mode 2.

Raspberry pi: connected Coordinator XBee to one of my RPi. You can see more about the connection in one of my earlier post.

Arduino Uno: connected the Router xbee to one of my Arduino. The connection is pretty simple as below.

  • XBee Rx –> Arduino Tx
  • XBee Tx -> Arduino Rx
  • XBee 3.3v-> Arduino 3.3v
  • XBee Gnd –>Arduino Gnd


Raspberry Pi Node js code

Modules used

  • xbee-api: npm install xbee-api
  • serialport: npm install serialport


var util = require('util'); var SerialPort = require('serialport').SerialPort; var xbee_api = require('xbee-api'); var C = xbee_api.constants; var xbeeAPI = new xbee_api.XBeeAPI({ api_mode: 2 }); var serialport = new SerialPort("/dev/ttyAMA0", { baudrate: 9600, parser: xbeeAPI.rawParser() }); var frame_obj = { type: 0x10, id: 0x01, destination64: "0013A200407A25AB", broadcastRadius: 0x00, options: 0x00, data: "MTON" }; serialport.on("open", function () { serialport.write(xbeeAPI.buildFrame(frame_obj)); console.log('Sent to serial port.'); }); // All frames parsed by the XBee will be emitted here xbeeAPI.on("frame_object", function (frame) { console.log(">>", frame); if(!== undefined) console.log('utf8')); });



Arduino Sketch

This sketch uses a XBee library, to add the library, goto Sketch->Include Library->Manage Libraries. From the window search for XBee and install the library. I am using Arduino IDE 1.6.7.

I use SoftwareSerial to establish serial communication with XBee, Pin 2 is Arduino Rx and Pin 3 is Arduino Tx.


#include <Printers.h> #include <XBee.h> #include <SoftwareSerial.h> unsigned long previousMillis = 0; const long interval = 4000; // the interval in mS XBee xbee = XBee(); // XBee's DOUT (TX) is connected to pin 2 (Arduino's Software RX) // XBee's DIN (RX) is connected to pin 3 (Arduino's Software TX) SoftwareSerial soft(2,3);// RX, TX Rx16Response rx16 = Rx16Response(); ZBRxResponse rx = ZBRxResponse(); XBeeAddress64 addr64 = XBeeAddress64(0x0013a200,0x407a25b5); char Buffer[128]; char RecBuffer[200]; void setup() { // put your setup code here, to run once: soft.begin(9600); Serial.begin(9600); xbee.setSerial(soft); } void print8Bits(byte c){ uint8_t nibble = (c >> 4); if (nibble <= 9) Serial.write(nibble + 0x30); else Serial.write(nibble + 0x37); nibble = (uint8_t) (c & 0x0F); if (nibble <= 9) Serial.write(nibble + 0x30); else Serial.write(nibble + 0x37); } void print32Bits(uint32_t dw){ print16Bits(dw >> 16); print16Bits(dw & 0xFFFF); } void print16Bits(uint16_t w){ print8Bits(w >> 8); print8Bits(w & 0x00FF); } void loop() { // put your main code here, to run repeatedly: xbee.readPacket(); if (xbee.getResponse().isAvailable()) { if (xbee.getResponse().getApiId() == ZB_RX_RESPONSE) { xbee.getResponse().getZBRxResponse(rx); if (rx.getOption() == ZB_PACKET_ACKNOWLEDGED) { // the sender got an ACK Serial.println("got ACK"); } else { // we got it (obviously) but sender didn't get an ACK Serial.println("not got ACK"); } Serial.print("Got an rx packet from: "); XBeeAddress64 senderLongAddress = rx.getRemoteAddress64(); print32Bits(senderLongAddress.getMsb()); Serial.print(" "); print32Bits(senderLongAddress.getLsb()); Serial.println(' '); // this is the actual data you sent Serial.println("Received Data: "); for (int i = 0; i < rx.getDataLength(); i++) { print8Bits(rx.getData()[i]); Serial.print(' '); } //Received data as string to serial Serial.println(' '); Serial.println("In string format"); for (int i = 0; i < rx.getDataLength(); i++) { if (iscntrl(rx.getData()[i])) RecBuffer[i] =' '; else RecBuffer[i]=rx.getData()[i]; } Serial.println(RecBuffer); String myString = String((char *)RecBuffer); if(myString=="MTON"){ Serial.println("Switching on Motor"); } else if(myString=="MTOFF"){ Serial.println("Switching off Motor"); } } //clear the char array, other wise data remains in the //buffer and creates unwanted results. memset(&RecBuffer[0], 0, sizeof(RecBuffer)); memset(&Buffer[0], 0, sizeof(Buffer)); } //Send a packet every 4 sec. unsigned long currentMillis = millis(); if (currentMillis - previousMillis >= interval) { // save the last time you blinked the LED previousMillis = currentMillis; strcpy(Buffer,"RSLOW"); uint8_t payload[20]= "RSLOW"; // ZBTxRequest zbtx = ZBTxRequest(addr64,(uint8_t *)Buffer,sizeof(Buffer)); ZBTxRequest zbtx = ZBTxRequest(addr64,payload,sizeof(payload)); xbee.send(zbtx); } }


Burn the sketch to Arduino.


Run node js code in RPi and you start receiving the frames from Arduino.



Happy coding….

Written by Sony Arouje

January 21, 2016 at 12:06 am

Raspberry Pi as a Development Server

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In my searches, I came across a very elaborate blog about Raspberry pi and how to utilize this small computer for development purpose. Also the post touches topic about how to configure Port forwarding to access the Pi from Internet.

Worth reading the blog: How to Turn Your Raspberry Pi Into a Development Server


Happy coding…

Written by Sony Arouje

October 30, 2015 at 10:55 am

Posted in Raspberry Pi

MQTT Protocol for Internet of Things (IoT)

with 8 comments

I was thinking about how to control my Aeroponic system remotely via internet. The Raspberry Pi controlling the system is connected to internet via a router. I could access RaspberryPi by Port forwarding and stuff like that but it’s complicated. Next option could be using Websockets but I felt it’s an overkill for the applications running in Pi.

Recently I received a Refcard from Dzone regarding a protocol called MQTT. I was not aware of this Protocol before. So thought of doing some experiment with it. I am not going much deeper into the protocol, Dzone refcard did a great job of explaining it well.

In a nutshell, MQTT consist of three parts.

  • Broker
  • Subscribers
  • Publishers



Publisher, publish message to a specific topic and any Subscriber subscribes for that topic receives the message. Broker is the central hub, both Publishers and Subscribers are connected to the Broker and it take care of delivering the message to all the subscribers subscribed for the topic.


We can implement our own broker using RabitMQ or Mosca plugin for Node js or any other MQTT brokers available in the market. To experiment it, I used CloudMQTT addon in Heroku. I used Heroku just to manage every thing from one central place.

Dev Environment

I created two set off Node js application, one running in my computer as a publisher and another running in my RaspberryPi as a subscriber. Both have no direct connection instead they are connected to CoudMQTT broker. Below is a test code and nothing related to my Aeroponic system.

Publisher Code

var mqtt = require('mqtt');
var client = mqtt.createClient('<<PortNumber>>', '', {
    username: '<<UserName>>',
    password: '<<Password>>'

client.on('connect', function () { // When connected
    // subscribe to a topic
    client.subscribe('TEMPERATURE_READING', function () {
        // when a message arrives, do something with it
        client.on('message', function (topic, message, packet) {
            console.log("Received '" + message + "' on '" + topic + "'");
    // publish a message to a topic
    client.publish('SET_TEMPERATURE', '24', function () {
        console.log("Message is published");


The above code act as a Publisher as well as a Subscriber. For e.g. the above code can be a piece running in Internet and the Pi’s can Publish the Temperature readings in a periodic interval and logged in a central db. We can see the readings via a webapp or which ever the way we need. Also if required we can set a temperature to all the connected RPi’s by publishing a message to topic ‘SET_TEMPERATURE’.

Subscriber Code

var mqtt = require('mqtt'), url = require('url');
var client = mqtt.createClient('<<Portnumber>>', '', {
    username: '<<UserName>>',
    password: '<<Password>>'

client.on('connect', function () { // When connected
    // subscribe to a topic
    client.subscribe('SET_TEMPERATURE', function () {
        // when a message arrives, do something with it
        client.on('message', function (topic, message, packet) {
            console.log("Received '" + message + "' on '" + topic + "'");
           // set the temperature. 


The code is very minimal and we could achieve an easy communication to all the connected devices. In the above scenario clients are always connected. If you want to end the connection then call ‘client.end()’.

Later I implemented a Broker using Mosca, both scenarios the system worked really well.

Written by Sony Arouje

September 3, 2015 at 5:29 pm

Posted in Raspberry Pi

Tagged with ,

RS485 Communication Protocol with Micro Controllers and Raspberry pi

with 8 comments

We are in the age of connected devices, devices could talk each other either via RF or wired. In one of my post I explained about Radio Frequency communication using Xbee. In this post lets see how devices can talk each other via wired network. One of the advantage of Wired network is, it is cost effective compare to buying an XBee modules like Xbee pro. I personally prefer Wireless communication as it’s hassle free, just place the devices where ever we need.

In my previous post I explained how to Bootload Atmega16A and program it using Arduino. Next step is to establish the communication between the Micro controllers and Raspberry pi. In this case my Raspberry Pi is acting as the central hub that talk to other controllers and collect data or issue command to do some job.

RS 485 Protocol

I better leave it to Wikipedia to give a detailed explanation of the protocol. In brief using RS485, devices can communicate Full duplex or Half duplex. I used a Half duplex communication. So it’s a protocol, how do we implement the protocol in our hardware, there is a chip Max485 from Maxim. This chip can establish a half duplex communication.

Max485 Pin configuration

Max 485 is a 8 pin chip as shown below. It’s a DIP chip and SMD have different pin layout.


Image from Maxim site

Pin 1 – RO: It’s the Data-In pin, devices can read data from the bus using this pin. Rx pin of the Micro controllers should connect to this pin.

RE and DE: Set this pin to Logical High to transmit any data to the bus. Set this pin to Low to receive data from the bus.

Pin 4 DI: Devices can transmit data via this pin.  This pin should be connected to the Tx pin of the device.

Pin 8 and 5 – VCC and GND: To power the chip, VCC should be 5 volt.

Pin 7 and 6 – A and B: Here we connect the data line. A should connect to the A Pin of the next Max 485 and B with B.


Connection Diagram

The below picture will illustrate how to connect all the devices together.


Image created using Fritzing

As per the diagram, if RPi want to transmit any data. We should set a high voltage on GPIO 18 and issue a serial write. All other devices in the network will be in listening mode and can read data using serial read, if any other device wanted to transmit data, then issue a Logical High to RE DE pin and will get promoted as a master and transmit data via serial write.

Now it’s up to you to program it and do some cool things with it.

Written by Sony Arouje

April 23, 2015 at 11:05 pm

Water Level Sensor for my Aeroponic– First Experiment in PCB design

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Last couple of weeks in my free times I was learning PCB design and basic Electronics. I studied basic electronics in College but that’s only to pass the exam. A couple of weeks ago, when I decided to learn basics of electronics, the only component I knew was Resistor. Rest I learned from YouTube and other blogs.

Next step was PCB Design, I went through so many YouTube videos and created so many designs using Eagle CAD (used Community Edition) and redo the design in several different ways. After some days of experiments with Eagle I was some what confident to design something that I could use in my Aeroponic system, a Water Level sensor. I cant design an electronic circuit but I learn to read Schematic designed by experts in Electronics.

I started searching for a right design for me to try out. I prototyped several design in breadboard but none of them worked as per my requirement. After several trial and error I finalized the below design I copied from one of the site, unfortunately I don’t know from where I copied the schema. (I will refer the url if I get that page again.)


Note: Above is a schema I created in Eagle cad, original author’s schema was very beautiful. Also I didn’t spend much time in schema, my goal was to design the PCB.

PCB Design

The next step was my area of interest, the PCB design. Below is the design I came up after several rearrangements of components.



PCB Etching

There are so many videos in YouTube detailing the PCB Etching process. I decided the approach of Laser printing the design on a glossy paper and doing thermal transfer to copper clad board. My friend Vinod, took a print out of the design on a Magazine cover. Yesterday night, with the help of Pressing iron and some Ferrous chloride, I created my first PCB. It’s a WOW moment for me.



I dill the holes using my Dremel rotatory tool. I added a Silk Screen as well. Printed the top screen in mirror mode on a Glossy paper and transfer to the board using my Wife’s Nail polish remover, It worked, you can see the silk screen in the below picture.

Final Board


Yes it’s a pretty simple circuit but I learned a lot from all these experiments.

Connecting to Raspberry Pi

The sensor will give two outputs, warning and critical status. Those two yellow wires are the sensor outputs, connect those to two GPIO pins of my pi. This is what I programmed.

1. Warning: The system will send a mail to me saying the water is below warning level.

2. Danger/Critical: The system will send a mail as well as shutdown the Submersible pump. If the pump run dry for a minute or two it will damage the pump.

3. When some one fill the tank with water above warning level, the motor will resume running and send a mail to me saying water level is fine.

Written by Sony Arouje

April 2, 2015 at 4:34 pm

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