It’s time to write about a more complex but interesting connection with the STM32F4-Discovery board. Since I started developing with electronics, I’ve found a lot of applications in which an LCD is needed or can be an added value, specially if it includes a Touchscreen.
The HC-SR04 ultrasonic sensor uses sonar to determine distance to an object. It offers excellent non-contact range detection with high accuracy and stable readings in an easy-to-use package, from about 3cm to 300cm. Its operation is not affected by sunlight or black material like other kind of sensor, although acoustically soft materials like cloth can be difficult to detect – at least in the far range. It comes complete with ultrasonic transmitter and receiver module.
The DHT22 (also known as AM2302) is a cheap temperature and humidity sensor with an impressive performance! It uses a capacitive humidity sensor and a thermistor to measure the air, and send out a digital signal on the data pin (no analog input pins needed). Its fairly simple to use, but requires careful timing to grab data. The only real CON of this sensor is that you can only get new data from it once every 2 seconds. It is provided with a single wire digital interface. The sensor is calibrated and only requires a single pull-up resistor (any value between 3.6k and 10k should work fine) on the dataline to communicate correctly. Compared to the cheaper (and wider diffused) DHT11, this module is much more precise, more accurate and works in a bigger range of temperature/humidity.
Most breadboards are not equipped with a power supply circuit. Every electronic enthusiast uses a breadboard since they are a fundamental tool to develop in a fast and easy way. Some problems arise when we need to work with devices not powered from the USB port or that need other supply voltages than 5V, so I decided to add a simple power supply to my large breadboard.
“Radio-frequency identification (RFID) is the wireless non-contact use of radio-frequency electromagnetic fields to transfer data, for the purposes of automatically identifying and tracking tags attached to objects. The tags contain electronically stored information. Some tags are powered by and read at short ranges (a few meters) via magnetic fields (electromagnetic induction). Others use a local power source such as a battery, or else have no battery but collect energy from the interrogating EM field, and then act as a passive transponder to emit microwaves or UHF radio waves (i.e., electromagnetic radiation at high frequencies). Battery powered tags may operate at hundreds of meters. Unlike a bar code, the tag does not necessarily need to be within line of sight of the reader, and may be embedded in the tracked object.
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