DHT11 based remote temparature Monitor. Uses ESP8266 and DHT11 to monitor temperature remotely using a WiFi connection and Thingspeak and NMA application.

1. Remote Temperature Monitor
Prepared by : Parshwadeep Lahane

2. Summary
• The project uses DHT11 and ESP8266 to monitor temperature at any point
of time
• The monitoring aspect has 2 objectives:
• To check temperature at any given point (achieved with the help of cloud connectivity through Thingspeak)
• To send an alert message when temperature exceeds a predefined value(achieved with the
help of Notify My Android app)

3. Things needed
6Pin USB 2.0 to TTL
UART Module Serial
Converter
HARDWARE
ESP8266 - 01
DHT11
Multi Power Supply
(5V and 3.3V)
Jumper wires Male to
Male
Jumper wires Female
to Female
Jumper wires Male to
Female
12V adaptor (1Amp)
Bread Board
Laptop
Breadboard Adapters
(optional)
WiFi connection
Any android mobile

4. Things needed
SOFTWARE
NodeMCU firmware (free)
Scripting language (free)
Account on Thingspeak (free)
Account on NMA (free)
Premium one at $5
Windows (any other
also would do)

5. Costing
• ESP8266 Rs300
• UART Rs180
• DHT11 Rs180
• Multipower supply Rs140
• 12V adapter Rs100
• Jumper wires(15) Rs50
• Bread board Rs120
• Premium NMA membership Rs350
TOTAL COST ~Rs 1500 or ~US $23
Note: The price quoted is as per what I got on SP road in Bangalore,India. It may be cheaper online/offline at other places so cost can come down further.
Assumptions:
1. WiFi connection already exists
2. Laptop with windows is available
3. Android Mobile phone available

6. 1.ESP8266
microcontroller from Chinese manufacturer Espressif that includes Wi-Fi capability
Cadence Tensilica LX106 microcontroller
• Operates at 3.3V
• Firmware upgrade is needed as first step after purchase
• GPIO 0 should be grounded for firmware upgrade mode
• RST and GPIO2 to be left open
• Connect RX of ESP8266 to TX of FT232RL
• Connect TX of ESP8266 to RX of FT232RL
• Supply external voltage of 3.3V to VCC and CH_PD
• GND to be connected to ground (FT232RL and ESP8266 ground should be
common)
Once the connections are done. RED LED on ESP8266 should be on. BLUE LED
will flash momentarily.
PIN PIN Description
VCC 3.3V
RST Reset (low active)
CH_PD Chip Power down (low active)
TXD Transmit data (3.3V level)
RXD Receive data (3.3V level)
GPIO 0 General Purpose Input / Output
GPIO 2 General Purpose Input / Output
GND Ground
Steps for firmware upgrade: http://www.whatimade.today/loading-the-nodemcu-firmware-on-the-esp8266-windows-guide/

7. 2. Lua
powerful, fast, lightweight, embeddable scripting language
What is Lua?
Lua is a powerful, fast, lightweight, embeddable scripting language.
Lua combines simple procedural syntax with powerful data description constructs based on associative arrays and
extensible semantics. Lua is dynamically typed, runs by interpreting bytecode for a register-based virtual machine, and has
automatic memory management with incremental garbage collection, making it ideal for configuration, scripting, and rapid
prototyping.
Where does Lua come from?
Lua is designed, implemented, and maintained by a team at PUC-Rio, the Pontifical Catholic University of Rio de Janeiro in
Brazil. Lua was born and raised in Tecgraf, formerly the Computer Graphics Technology Group of PUC-Rio in 1993. Lua is
now housed at LabLua, a laboratory of the Department of Computer Science of PUC-Rio.
What's in a name?
"Lua" (pronounced LOO-ah) means "Moon" in Portuguese. As such, it is neither an acronym nor an abbreviation, but a noun.
More specifically, "Lua" is a name, the name of the Earth's moon and the name of the language. Like most names, it should
be written in lower case with an initial capital, that is, "Lua".

8. 3. NodeMCU firmware upgrade
Lua based firmware for wifi-soc esp8266
• http://benlo.com/esp8266/esp8266QuickStart.html
• Plug the USB to serial adapter into your PC. Most adapters are automatically recognized by
Windows 7 and 8. Users of XP or older versions of Windows may need a driver which should be
supplied by the manufacturer of the USB adapter. The adapter will appear as a new COM port
on your system. Check the Device Manager if necessary.
• Run ESP8266Flasher.exe
• NodeMcuFlasher
• If you only have one COM device, the port will appear automatically. If you have more than one,
select the correct one from the drop down menu.
• The flasher program comes with default NodeMCU firmware in memory. This is unlikely to be
the latest version, but to get started quickly, use the default internal image. Later, you can
download the latest firmware, then select the [Config] tab and choose the new .bin file. Select
the 0x7C000 default and 0x7E000 blank sections. Uncheck the box for the 0x10000 IROM
section.
• Click on Flash(E) to start the programming process.
• https://www.youtube.com/watch?v=Gh_pgqjfeQc
• https://github.com/nodemcu/nodemcu-firmware
• https://bigdanzblog.wordpress.com/2015/04/14/installing-nodemcu-lua-firmware-on-esp8266-wifi-module/
• http://www.roboremo.com/flashing-nodemcu-firmware-to-esp8266.html
Videos:

9. If ESP8266 gets bricked what to do?
(Blue LED starts flashing on continuous basis)
• https://www.youtube.com/watch?v=VQ6-WrX54_s
http://www.xess.com/blog/esp8266-reflash/

10. Sketch for ESP8266 firmware upgrade
ESP 8266-01FT232RL
TXD
TXD
RXD
RXD
GND GND
GPIO 0
GPIO 2
+3.3V
Multi-Power
Supply
VCC CH_PD
GND
USBconnectiontoLaptop
3 pins used 7 pins used
Note: use a bread board to get connections in place.
A

11. 4.DHT11 Temperature and Humidity Sensor
GPIO 0 of ESP8266
along with ESP8266 and FT232 ground pins
5V External power supply
Basic working :
Note: now NodeMCU has built in DHT function so same can be used directly, Arduino also has one built in function

12. 5. ThingSpeak
The open data cloud platform for the Internet of Things
ThingSpeak API Quick Start
1. Sign Up for a ThingSpeak account
2. Go to Channels, and click New Channel
3. Complete the channel settings, and click Save Channel.
4. Update your Channel via URL:
5. https://api.thingspeak.com/update?api_key=YOUR_CHANN
EL_API_KEY&field1=7
6. View your Channel feed:
7. https://api.thingspeak.com/channels/YOUR_CHANNEL_ID/f
eeds.json
Video Link: https://www.youtube.com/watch?v=I_Jm6Q4z7ig

13. 6. Notify My Android(NMA)
platform that allows you to deliver push notifications from virtually any application to your Android device
NMA API Quick guide
1. Sign Up for a NMA account
2. Go to Manage API Keys and Generate New Key
3. Key details will appear in Key Description field.
4. Update NMA alerts via URL:
conn:send("GET /publicapi/notify?apikey=YOUR API KEY
&application=ESP8266&event=XXXX&description=text1%20tex
t2%20text3&priority=2rn HTTP/1.1rn")

14. 7. ESPlorer
Integrated Development Environment (IDE) for ESP8266 developers
• The essential multi-platforms
tools for any ESP8266 developer
from luatool author’s, including
a LUA for NodeMCU and
MicroPython.
• Download link :
• https://github.com/4refr0nt/ESPlorer
• http://esp8266.ru/esplorer/#download

15. Code (init.lua)
print("Setting up WIFI..")
wifi.setmode(wifi.STATION)
--modify according your wireless router settings
wifi.sta.config("SSID","PASSWORD")
wifi.sta.connect()
tmr.alarm(1, 1000, 1, function()
if wifi.sta.getip()== nil then
print("IP unavailable, Waiting...")
else
tmr.stop(1)
print("Config done, IP is "..wifi.sta.getip())
dofile("dht11.lua")
end
end)
Source: https://github.com/Parshwadeep/DHT11andESP8266andLuaandThingspeak/blob/master/init.lua
Change the RED part in your code

16. --- Get temperature and humidity data and send data to thingspeak.com
function sendData()
getTemp()
-- conection to thingspeak.com
print("Sending data to thingspeak.com")
conn=net.createConnection(net.TCP, 0)
conn:on("receive", function(conn, payload) print(payload) end)
-- api.thingspeak.com 184.106.153.149
conn:connect(80,'184.106.153.149')
conn:send("GET /update?key=YOUR_KEY&field1="..temp.."&field2="..humi.." HTTP/1.1rn")
conn:send("Host: api.thingspeak.comrn")
conn:send("Accept: */*rn")
conn:send("User-Agent: Mozilla/4.0 (compatible; esp8266 Lua; Windows NT 5.1)rn")
conn:send("rn")
conn:on("sent",function(conn)
print("Closing connection")
conn:close()
end)
conn:on("disconnection", function(conn)
print("Got disconnection...")
end)
end
-- send data every X ms to thing speak
tmr.alarm(2, 60000, 1, function() sendData() end )
Code (dht11.lua)
pin=3
m=0
function getTemp()
status,temp,humi,temp_decimial,humi_decimial = dht.read(pin)
if( status == dht.OK ) then
-- Float firmware using this example
print(string.format("DHT
Temperature:%d.%02d;Humidity:%d.%02drn",temp,temp_decimial,humi,humi_decimi
al))
if (temp >25) then
print ("ALERT: Temperature is out of range")
if m == 1 then
conn=net.createConnection(net.TCP, 0)
conn:on("receive", function(conn, payload) print(payload) end)
conn:connect(80,"50.116.34.97")
conn:send("GET
/publicapi/notify?apikey=YOUR_KEY&application=ESP8266&event=TEMP_ALERT&descri
ption=Temperature%20is%20more%20than%2025&priority=2rn HTTP/1.1rn")
conn:send("Host: notifymyandroid.comrn")
conn:send("Accept: */*rn")
conn:send("User-Agent: Mozilla/4.0 (compatible; esp8266 Lua; Windows NT
5.1)rn")
conn:send("rn")
m = 0
else m = 1
end
end
elseif( status == dht.ERROR_CHECKSUM ) then
print( "DHT Checksum error." );
elseif( status == dht.ERROR_TIMEOUT ) then
print( "DHT Time out." );
end
end
Source: https://github.com/Parshwadeep/DHT11andESP8266andLuaandThingspeak/blob/master/dht11.lua
Change the RED part in your code

17. Sketch for SW update and working model
ESP 8266-01FT232RL DHT11
TXD
TXD
RXD
RXD
GND GND GND
GPIO 0 Signal
+5V+3.3V
Multi-Power
Supply
VCC CH_PD
VCC
GND
USBconnectiontoLaptop
3 pins used 7 pins used 3 pins used
Note: use a bread board to get connections in place.
B

18. Important for software upload on ESP8266
• FIRST UPLOAD dht11.lua on ESP8266 by
clicking on Save to ESP in ESplorer.
• NEXT UPLOAD init.lua on ESP8266 by
clicking on Save to ESP in ESplorer.
• Wait for 1-2 min after upload. The setup
should work and updated data points
available on Thingspeak channel and
alerts on Notify My Android as per
distance monitored.

19. Sketch for post software update on ESP8266
ESP 8266-01 DHT11
GND GND
GPIO 0 Signal(S)
+5V+3.3V
Multi-Power
Supply
VCC CH_PD
VCC
GND
4 pins used 3 pins used
C

20. Tracking sensor data on ThingSpeak
Alerts on mobile with NMA app

21. In a Nutshell
• Get ESP8266 upgraded with NodeMCU firmware with help of UART (Sketch A)
• Open accounts on Thingspeak and Notify My Android App and get the API keys to be used
in code
• Connect DHT11 to ESP8266 and upload the code on ESP8266 using ESPlorer (Sketch B)
• Check the working of init.lua on serial monitor:
• Check Charts on Thingspeak
• Check condition of Mobile Alert when temperature is above a predefined value.
• Remove UART connections and check standalone working of ESP8266 and DHT11 (Sketch C)

22. Next Steps
• Get the things working on circuit board with minimal size
• Implement it in real server room/other environment

23. END