17. Applications ans implications¶

This week I worked on Applications and implications. The assignments are below :

What will it do ?¶

Measure the tension on the leash of a dog, send a signal when the tension decreases significantly.

Who’s done what beforehand ?¶

Nobody !

What will you design ?¶

A PCB and a box for the final object.

What materials and components will be used ?¶

100kg cell force
HX711 module
Led
Lithium rechargeable battery
3D printed Box

Where will come from ?¶

Electronics from Aliexpress
Materials from Agrilab
Ideas from me

How much will they cost ?¶

Connected object

Fonctions	Components	References	Price
Mesure strength	100kg Force sensor	100kg miniature pull pressure sensor	41.63€
Send a signal	Led	Led	0.10€
Data storage	Electronic card	Homemade PCB	To define regarding the materials used and the time spent to imagine, design and manufacturing
Data analysis	Software	Arduino IDE	free
Transmit the data	Bluetooth	ESP32	3,45€
Energy	Rechargeable battery	Battery	4.15€ each and I need 4 so 16.6€
Energy	Battery charger	Battery charger	5.65€

So I can estimate it around : 67.43€ without the homemade PCB and the engineering time spent on it but maybe the final product would cost around 130 euros to include the tradin margin and be economically sustainable for my business. I still have to define it because when I would create my business other costs would come.

What parts and systems will be made ?¶

The code, the hardware, the packaging.

What processes will be used ?¶

Electronic design and production, 3D design and printing, Embedded programming, Output and Input devices, Networking and Communications…

What questions need to be answered ?¶

How to use a ESP32 Wroom with a Cell force HX711 module (code) ?
What kind of battery controller use for my Lipo rechargeable battery ?
What kind of box should I do ?
How to send datas with bluetooth from ESP32 to MIT app and turn it into graphs ?

How will it be evaluated ?¶

If the object can measure force and send a signal if this one decrease.

Final plan :¶

Home made PCB¶

I have my final electronic card : BlueWhale equipped of a ESP32 Wroom module for Bluetooth and Wifi, connectors and an electrical voltage divider bridge for my input.

I still have to make to final connections between the input and output on that card and check if it goes right.

For the input connections :

Input and Output :¶

Regarding the time left and my objectives, I decide to modified a little bit my final project :

My input is still a 100kg micro compression and tension force sensor working with a HX711 module to measure the tension in continue on the leash of a dog.

Flashing the board with the input :

But my output changed, it would be a led shining when the tension decreases significantly.
The code is still in progress. I have to improve my input code and make a connexion between my input and my output code.

Here is my input code, I have some “magic numbers” that I should put into a constant at the begining :

#include "HX711.h" // the library required to use the HX711

// HX711 circuit wiring
const int LOADCELL_DOUT_PIN = 3;
const int LOADCELL_SCK_PIN = 2;

HX711 scale;

void setup() {
  Serial.begin(9600);
  scale.begin(LOADCELL_DOUT_PIN, LOADCELL_SCK_PIN);
}

void loop() {

  if (scale.is_ready()) {
    long reading = scale.read();
    float conversion = ((reading + 122700.)/ 320200 * 10.)*0.724; // modifie the values regarding your "zero" value and your weight standard
    Serial.print("HX711 reading: ");
    Serial.println(conversion);
    //Serial.println(reading);
  } else {
    Serial.println("HX711 not found.");
  }
  delay(100);
}

Design a Box¶

I still have to design a box for my connected object regarding the dimensions of my components !