Posts in Arduino
Arduino Pitot Tube Wind Speed and Airspeed Indicator - Theory and Experiments

The pitot tube is a device used to approximate the speed of vehicles traveling by air and water. An in-depth article on NASA's website is dedicated to pitot tubes (also called pitot-static tubes, Prandtl tubes), where it cites the primary application as airspeed indicator on aircraft. For more information on design and limitations of the instrument, I recommend perusing that page. For this tutorial, only the basic theory is explored using Bernoulli's equation and a practical application. An inexpensive pitot tube and a digital differential pressure sensor are used to measure pressure, which is converted to a digital signal using an Arduino board.

Arduino Thermistor Theory, Calibration, and Experiment

Thermistor, whose name is derived from a combination of thermal and resistor, is a temperature sensing device that registers changes in internal resistance as a function of temperature. Thermistors are often chosen over thermocouples because they are more accurate, have a shorter response time, and are generally cheaper. For most applications, thermistors are the smart and easy selection for temperature sensing below 300 degrees Celsius. In our case, we will be using a Negative Temperature Coefficient (NTC) thermistor, where the resistance decreases as the temperature increases. NTC thermistors are most common in commercial products that operate in the tens of degrees like thermostats, toasters, and even 3-D printers. An NTC 3950 100k thermistor will be used, which is designed for 100kOhm resistance at 25 degrees Celsius. This tutorial will introduce methods for relating resistance to temperature by fitting factory calibration data. The performance of the thermistor will also be evaluated using an Arduino board and a simple Newton’s law of cooling experiment.

Joshua Hrisko
NodeMCU Tutorial Series Part II: NodeMCU Server Control Over Local Area Network

This tutorial takes full advantage of the ESP8266 WiFi chip by serving a local webpage to control the general purpose input and output (GPIO) pins on a NodeMCU microcontroller. Some basic HTML and CSS programming methods will be utilized to create a stylish webpage that is both asynchronous (AJAX) and input-driven - this will give the user the ability to control the pins on the microcontroller. For the current example, an electromagnet and LED will be controlled using pulse width modulation (PWM) and simple high/low logic, respectively. The PWM control allows the user to change the voltage to the component, altering the magnetic field of the electromagnet. For the LED, the traditional digitalWrite() method will turn the LED on and off.

Joshua Hrisko
NodeMCU Tutorial Series Part I: Arduino IDE and Blinking an LED

NodeMCU is a WiFi platform that integrates the ESP8266 system on chip hardware with the familiarities of open-source software. The NodeMCU is powerful because it endows users with the ability to create Internet of Things (IoT) projects at a relatively low cost with tools readily available and open to the maker community. NodeMCU is fully compatible with the Arduino IDE, which is the method for programming the board in this tutorial.

Joshua Hrisko
iPhone Datalogger with Arduino Using The iOS Bluetooth App BLExAR

The BLExAR app will be used in conjunction with a CC2541 (HM-10, JDY-08, AT-09, SH-M08) Bluetooth module and an Arduino (ATmega328) board to create a simple data acquisition system. A DHT22 sensor will provide temperature and humidity data to the Arduino which will be recorded by an iOS device via the BLExAR app. This experiment is a real-world example of an Arduino application demonstrating data acquisition from a real sensor. This tutorial will allow users to solve their own engineering problems using the modern Arduino platform and wireless communication through the BLExAr app, which will ultimately expand the reach and compatibility of technology in the classical sciences through exploration and experimentation.

4-Pin RGB LED Control Using iOS BLExAR App, HM-10 Bluetooth Module, and Arduino

Control an RGB LED using three PWM pins on an Arduino Uno board via Bluetooth communication. An RGB LED is a single casing with three cathode (or anode) pins and one anode (or cathode) pin. This results in a 4-pin LED. In this tutorial, I will be using an RGB LED with three anodes and one common cathode. This means that we can change the color of the LED to over 16.7 million different variations (assuming each anode produces a different luminosity for each voltage change of the Arduino PWM pin). This tutorial will help demonstrate the power of the BLExAR app, and the flexibility of an Arduino board under iOS Bluetooth control. In my case, I will be using an iPhone with the BLExAR app, but an iPad would suffice as well.

Joshua Hrisko
iOS and Arduino Bluetooth Communication Using The BLExAR App and CC2541 Module

An app called “BLExAR” allows Arduino users to communicate to an iOS device (iPhone or iPad) using a Bluetooth CC2541 module (different versions are called: HM-10, SH-M08, AT-09, or JDY-08). The app permits control of an Arduino board, wireless serial communication, and data acquisition. Click on the app logo shown here to download the app, as it will be used as the iOS communication software. On the Arduino side, we need to wire the CC2541 Bluetooth Low Energy (BLE) module to an Arduino board and upload the appropriate software via the Arduino IDE. In this tutorial, we will demonstrate how to verify communication between an Arduino and CC2541 Bluetooth module, and then use Bluetooth communication to send strings between an iOS device and the Arduino ATmega328p board.

Joshua Hrisko
Arduino SoftPot LED Meter (Membrane Potentiometer)

How to use a soft, circular-membrane potentiometer with an Arduino board. Potentiometers function by altering the voltage of a system by mechanically changing the resistance associated with a voltage divider. In a traditional potentiometer (think of turning a volume knob), we are physically changing the voltage of a system. In the case of a soft potentiometer (where the name SoftPot comes from), we are altering the resistance of the voltage divider by physically depressing the potentiometer, thereby changing the resistance at a contact point. The working principle is exactly the same, but in the SoftPot’s case, we are pressing, and for a knob we are rotating.