Category Archives: Components

Using a TCRT5000 sensor with your Arduino

You need to know if an object is close to another one but without using a contact switch? The TCRT5000 sensor is a great and cheap option for that! It essentially consists into 2 parts bundled together: an infrared emitter and a photo-transistor.   Drawing 1: No object close to sensor Drawing 2: An object is close to the sensor,… Read more »

Using a Real-Time Clock (RTC) – NXP PCF8563P – with an Arduino

In this post, I will explain what a Real-Time Clock (RTC) is about and how to use it in your circuits. I will be using the NXP PCF8563P chip for the examples. You can find the data sheet for that chip here. A RTC is used to keep track of date & time in your circuit and make it available… Read more »

Police Car Strobe Lights using a 555 Timer and a 4017 Decade Counter

Introduction Today, we will solve the mystery behind police cars strobe lights! Seriously, I was looking at a way to simulate those lights using simple LEDs and without any rotating components. Here’s the result on a breadboard: Solution The solution to that problem was pretty simple. I used a 555 timer to trigger a 4017 decade counter. I used 4… Read more »

Adding pins to your Arduino using I2C and a PCF8574P chip

You are working on a project built around an Arduino and you realize you won’t have enough I/O pins to do everything? There are different ways of working around that limitation. One of them is to use an Inter-Integrated Circuit (I2C) bus and a PCF8574P chip. That chip will provide you with an additional 8 I/O pins at the cost… Read more »

IoT Object : ESP8266 + DHT-11 on

      No Comments on IoT Object : ESP8266 + DHT-11 on

There’s a lot of buzz around the Internet of Things (IoT) these days. This post explains how to create your own IoT object that will read your house air temperature and humidity and send that information to a web site called Once your data is on ThingSpeak, you’ll be able to visualize it to see how the your house… Read more »

Introducing the 4017 Decade Counter

      No Comments on Introducing the 4017 Decade Counter

The 4017 decade counter is a chip typically used for 10 of its output pins. It turns them on, only one at the time, in a sequence from 0 to 9. The chip waits for an external signal to switch to the next pin. Pinout Power Pins: – Pin #16 (VCC): Connect to VCC – Pin #8 (GND): Connect to… Read more »

Using 555 Timer/Oscillator

      No Comments on Using 555 Timer/Oscillator

The NE555 timer is one of the most popular Integrated Circuit (IC) out there.  It is sold since 1971, so it’s not exactly a new IC but it still does his job very well!  Even today, over a billion units are produced every year! The 555 timer is an integrated circuit that can be used to produce different kinds of… Read more »

What are pull-up and pull-down resistors?

      2 Comments on What are pull-up and pull-down resistors?

Let’s take that example. If we try to read the voltage at v1, with our ATtiny micro-controller, surprisingly we can’t tell what the voltage will be. It may be at 0 Volts, sometimes, and 2.9 Volts or 4 Volts at other moments. It’s voltage is undefined and varies depending on what surrounds it, like any electromagnetic field. This is what… Read more »

Using a regulator to control DC voltage

      No Comments on Using a regulator to control DC voltage

When designing a new circuit, we have to make sure we provide the right voltage level to all the components being used.  Some components may require a specific voltage like 1.8V, 3.3V or maybe 5V.  If you do not respect that constraint, your components won’t survive for a long time! I find using voltage regulators is the simplest and least… Read more »

Protecting your circuit with a diode

      No Comments on Protecting your circuit with a diode

A common mistake I do is to connect the power wires or battery the wrong way to a circuit. This results in reversed polarity and it may damage some components on your PCB or have even worst consequences. The good news is that we can very easily protect our circuits from such errors by using a rectifier diode.  It allows the… Read more »