Découvrez notre Chaîne YouTube "Ingénierie et Projets"
Découvrez notre Chaîne Secondaire "Information Neuronale et l'Ingénierie du Cerveau"

Capteur de toucher avec Arduino et ADS1115

Objectifs

  • Savoir les caractéristiques techniques du convertisseur ADC ADS1115
  • Savoir configurer le gain et la fréquence d’échantillonne du convertisseur ADS1115
  • Savoir programmer le convertisseur avec Arduino
  • Savoir utiliser le convertisseur comme capteur de touché
  • Etc.

Vidéos démonstration

Les caractéristiques techniques du convertisseur A/N ADS1115

Capteur de toucher avec Arduino

Les composants ADS1113, ADS1114 et ADS1115 (ADS111x) sont des convertisseurs analogique-numérique (CAN) ou (ADC) d’une résolution de 16 bits d’une grande précision, compatibles avec l’interface I2C. Le convertisseur intègre une référence de tension à faible dérive et un oscillateur. Le ADS1114 et ADS1115 également intègrent un amplificateur à gain programmable (PGA) et un comparateur numérique. Ces deux fonctionnalités d’un large domaine d’application rendent l’ADS111x bien adapté aux applications des capteurs à contraintes de puissance e et de l’encombrement.

L’ADS111x effectué des conversions avec des débits de données supérieurs à 860 échantillons par seconde (SPS). La tension à l’entrée du PGA variée de ± 256 mV à ± 6.144 V, ce qui permet la mesure des signaux de grandes ou petites amplitudes. L’ADS1115 est doté aussi d’un multiplexeur à l’entrée (MUX) qui permet d’avoir 2 entrées différentielles ou 4 en mode single.  Ci-dessous les caractéristiques techniques du composant et son datasheet.

ADS1115 PINOUT

  • Package: X2QFN: 2 mm × 1,5 mm × 0,4 mm
  • Résolution binaire: 16 bits
  • Amplificateur à gain programmable intégré PGA (8 gains)
  • Tension d’alimentation: 2,0 V à 5,5 V
  • Courant nominal: 150 μA (Mode de conversion continue)
  • Débit de données programmable: 8 SPS à 860 SPS
  • Règlement à cycle unique
  • Référence de tension interne à faible dérive
  • Oscillateur interne
  • Interface I2C: adresses sélectionnables à quatre broches
  • Quatre entrées asymétriques ou deux entrées différentielles (ADS1115)
  • Comparateur programmable (ADS1114 et ADS1115)
  • Température de fonctionnement: –40 ° C à + 125 ° C
  • Autres: Voir le datasheet

Amplificateur à gain programmable (PGA)

Le circuit dispos de trois bits de contrôles dédiés à la configuration du gain de l’amplificateur en aval du convertisseur A/N interne du circuit. Le PGA permet d’augmenter la précision de la mesure. En effet grâce à l’utilisation du PGA, le convertisseur peut mesurer des tensions de l’ordre de 7.8125 μV (Fort gain). Ci-dessous le tableau récapitulatif de la précision et la dynamique de mesure en fonction de l’état des bits.

GAIN Vs Dynamique de la mesure:

  • 000 : FSR = ±6.144 V(1)
  • 001 : FSR = ±4.096 V(1)
  • 010 : FSR = ±2.048 V (default)
  • 011 : FSR = ±1.024 V
  • 100 : FSR = ±0.512 V
  • 101 : FSR = ±0.256 V
  • 110 : FSR = ±0.256 V
  • 111 : FSR = ±0.256 V

Dynamique Vs Précision

PGA dynamique précision

Fonctionnement

Nous constatons pour un fort gain que le convertisseur peut mesurer une tension de l’ordre de 7.8µC qui n’est pas faisable pour les convertisseurs A/N de l’Arduino (Résolution 10 bits, précision d’environ 50mV). En effet grâce à l’ADS1115 on peut détecter des tensions de très faibles valeurs qui peuvent être manifestées lorsqu’un utilisateur touche une entrée analogique. Après des tests, nous constatons que la tension de l’entrée effectivement augmente lorsqu’on touche l’entrée. La variation est de l’ordre de 70-110mV lorsqu’on branche une résistance entre  l’entrée analogique (A0) et la masse, mais d’une valeur stable. La valeur mesurée est en revanche importante lorsque l’entrée est en air, par contre la valeur est fluctuante. Ci-dessous les deux configurations:

Entrée connectée - ADS1115 Entrée connectée - ADS1115.jpg

Programmation Arduino

Librairies Arduino

Programme principal commenté

#include <I2Cdev.h>


/*
-----------------------------------------------
Librairies Arduino 
-----------------------------------------------
I2C: https://github.com/jrowberg/i2cdevlib
ADS1115: https://github.com/addicore/ADS1115

-----------------------------------------------
Branchement Arduino-ADS1115:
----------------------------------------------- 
ADS1115 -->  UNO
  VDD        5V
  GND        GND
  SCL        A5 (or SCL)
  SDA        A4 (or SDA)
  ALRT       2
  
-----------------------------------------------
Paramètres du Gain: 
-----------------------------------------------
ADS1115_PGA_6P144           0x00
ADS1115_PGA_4P096           0x01
ADS1115_PGA_2P048           0x02 // default
ADS1115_PGA_1P024           0x03
ADS1115_PGA_0P512           0x04
ADS1115_PGA_0P256           0x05
ADS1115_PGA_0P256B          0x06

0 : FSR = ±6.144 V(1)
1 : FSR = ±4.096 V(1)
2 : FSR = ±2.048 V (default)
3 : FSR = ±1.024 V
4 : FSR = ±0.512 V
5 : FSR = ±0.256 V
6 : FSR = ±0.256 V
7 : FSR = ±0.256 V

-----------------------------------------------
Paramètres de la fréquence de mesure: 
-----------------------------------------------
ADS1115_RATE_8              0x00
ADS1115_RATE_16             0x01
ADS1115_RATE_32             0x02
ADS1115_RATE_64             0x03
ADS1115_RATE_128            0x04 // default
ADS1115_RATE_250            0x05
ADS1115_RATE_475            0x06
ADS1115_RATE_860            0x07

*/

#include "ADS1115.h"

ADS1115 adc0(ADS1115_DEFAULT_ADDRESS);

// Paramètres 
const int alertReadyPin = 2;
const int AlarmePin=3; 
double ADC_mV=0.0; 
double Seuil_Alarme_mV=50.0; 

void setup() {    
    //Connexion du bus I2C
    Wire.begin();

    // Init interface série 
    Serial.begin(115200); 

    // Test de la connectivité
    Serial.println("Testing device connections...");
    Serial.println(adc0.testConnection() ? "ADS1115 connexion réussie" : "ADS1115 connexion non établie");

    // Initiation du convertisseur ADS1115
    adc0.initialize(); 

    // Mode: Lecture unique (Il existe le mode continu!)
    adc0.setMode(ADS1115_MODE_SINGLESHOT);
    
    // Affectation de la fréquence d'échantillonnage (16SPS) 
    adc0.setRate(ADS1115_RATE_16);
      
    // Affectation du Gain
    adc0.setGain(ADS1115_PGA_0P512);

    // Connexion de l'indicateur de fin de conversion 
    pinMode(alertReadyPin,INPUT);
    adc0.setConversionReadyPinMode();

    // Alarme 
    pinMode(AlarmePin,OUTPUT);
}

void loop() 
{       
    // Sélection de l'entrée (A0)
    adc0.setMultiplexer(ADS1115_MUX_P0_NG);

    // Lancement de la conversion 
    adc0.triggerConversion();

    // Test la fin de la conversion 
    pollAlertReadyPin();

    // Lecture du convertisseur en mV
    ADC_mV=abs(adc0.getMilliVolts(false));

    // Affichage de la valeur acquise 
    Serial.print("A0: "); Serial.print(ADC_mV); Serial.println("mV");

    // Déclanchement de l'alarme 
    if (ADC_mV > Seuil_Alarme_mV)
    {
      digitalWrite(AlarmePin, HIGH);
    }
    else
    {
      digitalWrite(AlarmePin, LOW);
    }

    // Attente (Attention à la fréquence de la mesure!)  
    delay(250);
}

// Fonction affichage de l'état de conversion après 100000 tentatives
void pollAlertReadyPin() 
{
  for (uint32_t i = 0; i<100000; i++)
    if (!digitalRead(alertReadyPin)) return;
   Serial.println("Failed to wait for AlertReadyPin, it's stuck high!");
}

Photo du projet

lecture du convertisseur

projet capteur de toucher avec arduino nano

projet capteur de toucher avec arduino nano

Téléchargement du projet

Tout les projets microcontrôleur

 

 

Click to rate this post!
[Total: 1 Average: 5]

0 commentaire

Laisser un commentaire

Avatar placeholder

Votre adresse e-mail ne sera pas publiée. Les champs obligatoires sont indiqués avec *

Anti-Robot *

We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. We also share information about your use of our site with our social media, advertising and analytics partners.
Cookies settings
Accept
Decline
Privacy & Cookie policy
Privacy & Cookies policy
Cookie name Active

Privacy Policy

What information do we collect?

We collect information from you when you register on our site or place an order. When ordering or registering on our site, as appropriate, you may be asked to enter your: name, e-mail address or mailing address.

What do we use your information for?

Any of the information we collect from you may be used in one of the following ways: To personalize your experience (your information helps us to better respond to your individual needs) To improve our website (we continually strive to improve our website offerings based on the information and feedback we receive from you) To improve customer service (your information helps us to more effectively respond to your customer service requests and support needs) To process transactions Your information, whether public or private, will not be sold, exchanged, transferred, or given to any other company for any reason whatsoever, without your consent, other than for the express purpose of delivering the purchased product or service requested. To administer a contest, promotion, survey or other site feature To send periodic emails The email address you provide for order processing, will only be used to send you information and updates pertaining to your order.

How do we protect your information?

We implement a variety of security measures to maintain the safety of your personal information when you place an order or enter, submit, or access your personal information. We offer the use of a secure server. All supplied sensitive/credit information is transmitted via Secure Socket Layer (SSL) technology and then encrypted into our Payment gateway providers database only to be accessible by those authorized with special access rights to such systems, and are required to?keep the information confidential. After a transaction, your private information (credit cards, social security numbers, financials, etc.) will not be kept on file for more than 60 days.

Do we use cookies?

Yes (Cookies are small files that a site or its service provider transfers to your computers hard drive through your Web browser (if you allow) that enables the sites or service providers systems to recognize your browser and capture and remember certain information We use cookies to help us remember and process the items in your shopping cart, understand and save your preferences for future visits, keep track of advertisements and compile aggregate data about site traffic and site interaction so that we can offer better site experiences and tools in the future. We may contract with third-party service providers to assist us in better understanding our site visitors. These service providers are not permitted to use the information collected on our behalf except to help us conduct and improve our business. If you prefer, you can choose to have your computer warn you each time a cookie is being sent, or you can choose to turn off all cookies via your browser settings. Like most websites, if you turn your cookies off, some of our services may not function properly. However, you can still place orders by contacting customer service. Google Analytics We use Google Analytics on our sites for anonymous reporting of site usage and for advertising on the site. If you would like to opt-out of Google Analytics monitoring your behaviour on our sites please use this link (https://tools.google.com/dlpage/gaoptout/)

Do we disclose any information to outside parties?

We do not sell, trade, or otherwise transfer to outside parties your personally identifiable information. This does not include trusted third parties who assist us in operating our website, conducting our business, or servicing you, so long as those parties agree to keep this information confidential. We may also release your information when we believe release is appropriate to comply with the law, enforce our site policies, or protect ours or others rights, property, or safety. However, non-personally identifiable visitor information may be provided to other parties for marketing, advertising, or other uses.

Registration

The minimum information we need to register you is your name, email address and a password. We will ask you more questions for different services, including sales promotions. Unless we say otherwise, you have to answer all the registration questions. We may also ask some other, voluntary questions during registration for certain services (for example, professional networks) so we can gain a clearer understanding of who you are. This also allows us to personalise services for you. To assist us in our marketing, in addition to the data that you provide to us if you register, we may also obtain data from trusted third parties to help us understand what you might be interested in. This ‘profiling’ information is produced from a variety of sources, including publicly available data (such as the electoral roll) or from sources such as surveys and polls where you have given your permission for your data to be shared. You can choose not to have such data shared with the Guardian from these sources by logging into your account and changing the settings in the privacy section. After you have registered, and with your permission, we may send you emails we think may interest you. Newsletters may be personalised based on what you have been reading on theguardian.com. At any time you can decide not to receive these emails and will be able to ‘unsubscribe’. Logging in using social networking credentials If you log-in to our sites using a Facebook log-in, you are granting permission to Facebook to share your user details with us. This will include your name, email address, date of birth and location which will then be used to form a Guardian identity. You can also use your picture from Facebook as part of your profile. This will also allow us and Facebook to share your, networks, user ID and any other information you choose to share according to your Facebook account settings. If you remove the Guardian app from your Facebook settings, we will no longer have access to this information. If you log-in to our sites using a Google log-in, you grant permission to Google to share your user details with us. This will include your name, email address, date of birth, sex and location which we will then use to form a Guardian identity. You may use your picture from Google as part of your profile. This also allows us to share your networks, user ID and any other information you choose to share according to your Google account settings. If you remove the Guardian from your Google settings, we will no longer have access to this information. If you log-in to our sites using a twitter log-in, we receive your avatar (the small picture that appears next to your tweets) and twitter username.

Children’s Online Privacy Protection Act Compliance

We are in compliance with the requirements of COPPA (Childrens Online Privacy Protection Act), we do not collect any information from anyone under 13 years of age. Our website, products and services are all directed to people who are at least 13 years old or older.

Updating your personal information

We offer a ‘My details’ page (also known as Dashboard), where you can update your personal information at any time, and change your marketing preferences. You can get to this page from most pages on the site – simply click on the ‘My details’ link at the top of the screen when you are signed in.

Online Privacy Policy Only

This online privacy policy applies only to information collected through our website and not to information collected offline.

Your Consent

By using our site, you consent to our privacy policy.

Changes to our Privacy Policy

If we decide to change our privacy policy, we will post those changes on this page.
Save settings
Cookies settings

You have successfully subscribed to the newsletter

There was an error while trying to send your request. Please try again.

FPGA | Arduino | Matlab | Cours will use the information you provide on this form to be in touch with you and to provide updates and marketing.