iot and Robotics

My journey with iot and robotics (In Progress...)

I have been working in the data warehousing and Big data domain from quite a while and I did not get a chance to explore one of my childhood fantasy until, I went to my friend - Uday's home in Bengaluru to visit him. He introduced me to the world of IOT. I was awestruck when I saw a small pot lying on his desk and some electronics attached to it. When asked, he started explaining me that it was a humidity sensor and he would know from his office if some one watered the plant at home. That was fascinating. There was a weighing machine in his home which displays the weight on his computer and he records the time and weight information so that, he can analyze the information later. That was neat, as he do not have do a thing other than standing on the weighing scale.

I have got some inspiration from him but, I do not have any knowledge in electronics. 

1 Temperature and humidity sensor using NodeMCU

init.lua
 
function startup()
    if file.open("init.lua") == nil then
        print("init.lua deleted or renamed")
    else
        print("Running")
        file.close("init.lua")
        -- the actual application is stored in 'application.lua'
         dofile("application.lua")
    end
end

  print("10 secs to abort.")
  print("Waiting...") 
  tmr.create():alarm(10000, tmr.ALARM_SINGLE, startup)








application.lua
pin = 3

status, temp, humi, temp_dec, humi_dec = dht.read(pin)--read dht11 from pin

if status == dht.OK then    --check status is ok and print temperature and humidity
print(string.format("DHT Temperature:%d.%03d;Humidity:%d.%03d",
math.floor(temp),
temp_dec,
math.floor(humi),
humi_dec
    ))
elseif status == dht.ERROR_CHECKSUM then    --else print either status
print( "DHT Checksum error." )
elseif status == dht.ERROR_TIMEOUT then
print( "DHT timed out." )
end

2 Remote controlled car using Arduino uno

// Controlling RC with computer keyboard 
import time
import paho.mqtt.client as paho
import sys,tty,termios

broker="192.168.8.88"
#broker="iot.eclipse.org"
#define callback
def on_message(client, userdata, message):
    time.sleep(1)
    print("received message =",str(message.payload.decode("utf-8")))

client= paho.Client("client-001") #create client object client1.on_publish = on_publish #assign function to callback client1.connect(broker,port) #establish connection client1.publish("house/bulb1","on")
######Bind function to callback
client.on_message=on_message
#####
print("connecting to broker ",broker)
client.connect(broker)#connect
#client.loop_start() #start loop to process received messages
#print("subscribing ")
#client.subscribe("house/bulb1")#subscribe
#time.sleep(2)

class _Getch:
    def __call__(self):
            fd = sys.stdin.fileno()
            old_settings = termios.tcgetattr(fd)
            try:
                tty.setraw(sys.stdin.fileno())
                ch = sys.stdin.read(3)
            finally:
                termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
            return ch
exit_pressed = 0 
print("waiting for key press")
def send_cmd(cmd):
    client.publish("HOME/robot/cmd",cmd)#publish
    

def get():
        inkey = _Getch()
        while(1):
                k=inkey()
                if k!='':break
        if k=='\x1b[A':
                print ("FRONT")
                send_cmd("FRONT")
        elif k=='\x1b[B':
                print ("BACK")
                send_cmd("BACK")
        elif k=='\x1b[C':
                print ("RIGHT")
                send_cmd("RIGHT")
        elif k=='\x1b[D':
                print ("LEFT")
                send_cmd("LEFT")
        else:
                print ("not an arrow key! exiting")
                exit_pressed = 1

while (exit_pressed==0):
    print("waiting for key press")
    get()

print("Exiting..")
client.disconnect() #disconnect
client.loop_stop() #stop loop

3 Spider - 12 motor 4 legged robot using Arduino nano

4 E-Bike- Assembling e-bike kit

5. Raspberry Pi temperature using homebridge and Homekit [03 Sep 2019] 

 STEP 1 : Connect to your Pi using ssh

 ssh pi@raspberrypi.local

STEP 2 : Update pi

sudo apt-get update
sudo apt-get upgrade

STEP 3: Install node and npm (follow https://www.instructables.com/id/Install-Nodejs-and-Npm-on-Raspberry-Pi/)
Detech model of the ARM processor of Pi (ARMv6, ARMv7 or ARMv8)

uname -m

STEP 4: Depending  on the version, go to this page (node.js download page) and copy the link of corresponding. For instance, mine is ARMv7

 wget https://nodejs.org/dist/v10.16.3/node-v10.16.3-linux-armv7l.tar.xz

STEP 5: Extract the archive

tar xvf node-v10.16.3-linux-armv7l.tar.xz

STEP 6: Copy Node to /usr/local

cd node-v10.16.3-linux-armv7l/
sudo cp -R * /usr/local/

STEP 7: Check the versions of node and npm

node -v

npm -v

STEP 8: Homebridge installation

curl -sSL goo.gl/Ksdhph | bash

STEP 9: run Homebridge

homebridge

hit cntr + C to get back to Pi


Reference: https://github.com/nfarina/homebridge/wiki/Running-HomeBridge-on-a-Raspberry-Pi
STEP 10: Running Homebridge on Bootup (systemd)
Download 2 files: https://gist.github.com/johannrichard/0ad0de1feb6adb9eb61a/

Download the two files and place homebridge under /etc/default and 

homebridge.service under /etc/systemd/system on your Raspberry Pi from above link

STEP 11: Configuration
In order to use the systemd service as is, the following folders and user have to exists:

Create a system user named homebridge. You can easily create this user with

useradd --system homebridge  

Later, change the user permission from root user to homebridge

chown homebridge:homebridge homebridge

STEP 12: A directory called /var/lib/homebridge, writable by the user created above, and a corresponding config.json file in that directory. Homebridge by default looks for its configuration in /home/<username>/.homebridge. This is unsuitable for services and the -U /var/lib/homebridge flag ensures the config is read from a different place.

Here is the code for config.json. For validating json code use https://jsonlint.com/

{
 "bridge": {
  "name": "Homebridge8",
  "username": "CC:22:3D:E3:CE:30",
  "pin": "031-45-154",
  "port": 40853
 },
 "accessories": [{
  "accessory": "RaspberryPiTemperature",
  "name": "RaspberryPi CPU Temperature",
  "updateInterval": 1000
 }]
}

STEP 13: Install homebridge plugin for Pi temperature

 sudo npm install -g homebridge-raspberrypi-temperature

STEP 14: Now Enable and run the service (first time) with the following commands:

sudo systemctl daemon-reload
sudo systemctl enable homebridge
sudo systemctl start homebridge

STEP 15:  check the status of the service by calling

systemctl status homebridge

STEP 16: On subsequent reboots, it should start automatically, if not, use the following command to check the error cause.

journalctl -u homebridge

STEP 17: When the service starts successfully. It might look something like this

Now you can open your homekit and enter the code

Once done, you can now see the temperature showing up in your HomeKit App :)