Heat Index Monitoring System

Using Arduino Sensors
1

Good day!

I am a beginner in the forum and someone new to arduino, but I'm interested in building a Heat Index monitoring system using arduino, but I don't know what are the appropriate parts should I buy and expect.

I plan to set it in an outside environment, and scattered in places to gather the heat index in different parts in a university (all are battery powered).

The only parts I know of to use were:

DHT22 (temp sensor)
ESP8266 (for the wifi module)

The main goals were to record all the heat index recorded by the sensors (or devices), view what time was it recorded, from what device (or place) was it recorded, and can be monitored real-time

And what would be the substitute for ESP8266 if there is no available wifi. Would a GSM module be great? or LoRa?

All your insights would be of great help, and is greatly appreciated. Thank you so much in advanced.

Cheers.

2

To keep things simple, you should try to use only one sensor design. So if WiFi is not suitable for all locations, you could consider some other RF system like LoRa or HC-12.

WiFi would be simpler because each sensor can connect directly to a central server to log the data. With other RF types, you might need to build a gateway to receive data from sensors and forward it to the server via WiFi or wired network.

If WiFi signal is available but too weak in some locations, you could use external antenna to boost the signal. Wemos D1 Mini Pro allows an external antenna, for example. Various designs of external antenna are available with various gain values, and some are directional.

Do you know if there is a gateway in or near the university for LoRaWAN such as The Things Network? If so, you could use LoRa and use that gateway.

By the way, there are many other temperature/humidity sensors available than DHT22. For example SHT21/30/31, BME280....

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3

One sensor design... so its going to be like a uniform structure of device, but can be 1 or more? About that, what would be your suggested build of the device?

About the server, I'm planning to integrate Node.js to build the backend and would be able to record the data to the database of my choosing, but if those options were to be hard or unfeasible. Maybe I'll resort to IoT (please correct me if I'm taking things the wrong way, and thanks in advance too).

4

I'm assuming you would be using more than one ESP8266?

If so, and as you said it would be in an outside environment, I think the DS18B20 temperature sensor would be a good choice, as it's waterproof and provides 12 bit resolution if needed. DS18B20 also uses oneWire communication and each sensor has a unique 64-bit serial code, so you can label the sensors in each location and use that as reference to identify what sensors' data you are viewing. You can then associate a specific serial code to a specific location in your code, and use that during data transfer.

I would have an ESP connected to each sensor as a slave and have them send the data to a master ESP8266, that way you have all the data in a single board. You can also see what ESP board is sending the data.

You should also probably use an RTC for the timing, I'd recommend something like a DS3231 which has a TCXO for accurate timekeeping (~+-1 minute per year in the right conditions). As you are new, I'm assuming you don't know what a TCXO is. It stands for Temperature Compensated Crystal Oscillator. The DS3231 has a temperature sensor integrated into it to adjust the frequency of the crystal oscillator, which is used for timekeeping.

If you use ESPNOW, If what I'm reading online is correct, you don't need a wifi connection to connect the ESP8266's to one another. I've never used LoRa or GSM, but you could add an SD card module to the master ESP8266 and store all of the data on the SD card if wifi isn't available and you cannot connect to an online server.

Also, if WiFi is available, you could connect the master ESP8266 to an NTP server and calibrate the RTC's to the time that was retrieved from the server.

One more thing, you can create a web server/database on the ESP8266 master. I'm in the process of doing this- I'm using CSS, HTML and javascript all in an ESP on the Arduino IDE. That way, you can run a server/database directly where you are receiving data. If WiFi isn't available, store the data on the SD card, when WiFi is available, send the data from the SD card to the server/database (you can create a database on the ESP8266 via Arduino IDE using PHP and MySQL) and continue sending data to the server or database for as long as WiFi is available.

Edit: ESP-NOW has a range of around 220 metres, so if you need anything longer range then I’d consider some sort of RF

5

Be sure to get a reliable communication system going first otherwise you will be wasting a whole lot of time and effort for nothing.

6

if the university has local WiFi available around the campus use that (assuming you are allowed to connect to it)

if not consider ESP-MESH or LoRa-MESH

you will need to experiment to test the alternatives

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7

Thank you for the response, and I have taken interest with what you have doing too (the web server/database on the ESP8266), as with my current plans after consulting with some peers of mine, I have to ask, is utilizing the UNO r4 with WiFi a good choice to go? or will a simpler UNO with ESP8266 will do. As I'm thinking of either using the Arduino Cloud IoT or AWS to merge or use it to my web project. Is Using r4 or ESP32 a good choice? or will just using ESP8266 (which is cheaper, but said it can do its job) be a better choice considering the budget?

Thank you in advance and goodluck in your building journey!

8

I would tend to use an ESP8266 or ESP32 (which in addition to WiFi also has Bluetooth Classic and BLE) - both low cost (ESP8266 about £5 and ESP32 about £7 in UK) much lower cost than the UNO R4
would not consider a UNO with ESP8266 - the interprocessor communications makes the overall system much more complex

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9

So a final product can look like this?

DHT22 + ESP8266 + Battery Module (in case if power supply is not available)

If UNO with ESP8266 is not considerable, would using ESP32 as replacement would be better?

10

I would use ESP32 has it has more facilities than the ESP8266
never used a DHT22 - tend to use DS18B20 waterproof temperature sensor

11

ohhh okay, so an UNO is not needed at all right? even if my project would be deployed to various locations? Just the ESP32, the Temp sensor, the battery, the PCB (which is going to be soldered), then the case, am I right? Sorry I for the lack of knowledge with arduino, and thanks in advance for the responses!

12

no need for a UNO - the ESP32 should be OK
I assume the test locations have access to a local WiFi network
if so worth checking that the university will allow you to connect devices to their network

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13

okay okay, what kind of battery/power source can you suggest would be optimal for remote places?

14

have a look at Powering ESP32 Projects with Batteries

some ESP32 modules have a battery connector

15

Are you sure WiFi will work in all the places you plan on putting the sensors?

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for now, only one device is the plan or the least to be achieved, to deliver the essentials (which is to get the Temp and Humidity), but having more than one would be better, if wifi won't be available, maybe a gsm module or LoRaWAN (tho I'm still looking good gsm modules and LoRaWAN incase wifi is not available for different devices

17

Well, you can spend the rest of you life evaluating the pros and cons of the 100's of boards that are available for WiFi, LoRa and GSM.

18

Well, I won't be able to fit all of that within 4+ months, so i guess more research to go. But for now, i guess the ESP32 + Sensor + (a battery is what i need to find first to power-up the sensor and wifi module before the GSM module) battery/power supply.

19

you can do an implementation of the ESP32+senor assuming a WiFi network is available and test it - if all else fails using a low cost WiFi router
in your report you can mention alternative technologies such as LoRa, GSM, etc comparing costs, power requirements, ease of use, etc
all technologies have pros and cons
have a look at multi-radio-network-devices

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20

Yeah, I guess I can test it and see if in the places where I plan to put it have enough WiFi coverage (I mean having the system and the device to work is the main goal, to have more devices would help the data gathering better data wise). Lastly what battery setup would be great? I've read from the link you have sent earlier, but I can't decide which would be the most optimal, and how would be the setup, would it be like:

LiPo Pouch Cell
TP4056 Charging Module With Protection
3.3V Voltage Regulator (if TP4056 don't provide 3.3V output)