The HC-SR04 ultrasonic distance module is an inexpensive device to detect distances with centimeter accuracy, up to a few meters.
The device emits ultrasonic pulses of sound and listens for an echo. The echo time depends on the distance of the object that reflected the sound.
Transistors are just about everywhere in electronics. They are used in digital switches, amplifiers, voltage regulators, and many other simple components that work together in complex digital circuits. Two types you're likely to use are the bipolar junction transistor (BJT) and the field effect transistor (FET).
Both types of transistor have three pins. The pins on the bipolar junction transistor are called the emitter, collector, and base. On the field effect transistor, the pins are called the source, drain, and gate.
Stepper motors can move back and forth and lock into fixed positions, or steps, around the axis.
Stepper motors are common in machines that require precise and stable movement, like 3D printers and CNC machines.
Usually you will connect a stepper motor to your microcontroller by means of a stepper motor driver board, which has all the circuitry for controlling the motor. Then for you to control the motor, you just need to provide power and a signal to trigger the motor's intended position.
A shift register is a simple memory device that allows data to be "shifted" bit-by-bit into or out of the register.
One place you might use a shift register is to control up to eight components, such as LEDs, using only three Arduino pins instead of a separate pin for each LED. Moreover, some shift registers can be chained together to expose a huge number of inputs or outputs while using only a few pins on the microcontroller. Shift registers are also used for controlling 7-segment LCD displays and various other components.
Servo motors are an important part of many robotics projects. A servo can move to arbitrary positions within some range of motion, usually 180 degrees. You might think of them like mechanical elbows.
Most Arduino boards can only supply enough power to move very tiny servos (like the 9g variety for steering small RC vehicles) – and no more than one unless you are careful to move them one at a time. This is helpful for prototyping and debugging isolated parts of a larger robot before moving them off to a different circuit with external power.
At first glance, some rotary encoders look a lot like the potentiometers used as knobs on radios and other control boards. They both can serve a similar purpose in providing rotational information to a circuit. However, these components are fundamentally very different:
Rhasspy is a loosely connected set of tools for creating a personal voice assistant. Each of the tools, including speech recognition and speech generation, can run on your own computer without sending your private data off to a cloud-based service (although you can still choose to do so).
The components within Rhasspy's pipeline can talk to each other using various methods such as by posting data to a web URL or launching a program in response to a command.
Passive RFID tags are basically just little antennas with an extremely low power integrated circuit. When the IC is activated by power induced by the antenna, it generates a signal to transmit a small amount of data, such as an ID number.
This RC522 RFID module can read RFID tags and write to RFID tags that support writing. The RFID tag has a 4-byte (or 32-bit) UID, which means there are about 4.3 billion unique possibilities. Although that sounds like a lot, there are some situations where it's not considered enough to prevent collisions or brute-force guessing.
A passive infrared (PIR) motion sensor can detect changes in infrared radiation, most often in order to detect the motion or presence of people or animals.
The sensor can be thought of as a two-pixel infrared camera. It has two internal infrared sensors and circuitry to detect changes between them. The internal sensors are covered by a Fresnel lens that determines the PIR device's field of view.
The following relates specifically to the HC-SR501 model, but it should also apply to similar PIR motion sensors for hobbyists.
Node-RED is a browser-based programming tool for interacting with hardware devices, online services, and other software that you may be running. Programming is done using a combination of JavaScript and a visual programming language consisting of nodes that receive some kind of data, transform or act upon the data, and then send messages out to other connected nodes. These small programs are called flows.