HC-SR04 Ultrasonic Sensor Distance Measuring Module
                                    R26.36  Inc VAT                                
                                                    This economical sensor provides 2cm to 400cm of non-contact measurement functionality with a ranging accuracy that can reach up to 3mm. Each HC-SR04 module includes an ultrasonic transmitter, a receiver and a control circuit.
There are only four pins that you need to worry about on the HC-SR04: VCC (Power), Trig (Trigger), Echo (Receive), and GND (Ground). You will find this sensor very easy to set up and use for your next range-finding project!
Specifications
- Model: HC-SR04
 - Color: Blue Silver
 - Working voltage : 5V(DC)
 - Static current: Less than 2mA.
 - Output signal: Electric frequency signal, high level 5V, low level 0V.
 - Sensor angle: Not more than 15 degrees.
 - Detection distance: 2cm~450cm.
 - High precision: Up to 3mm
 - Mode of connection: VCC / trig(T) / echo(R) / GND
 - Module Working Principle:
 - Adopt IO trigger through supplying at least 10us sequence of high level signal
 - The module automatically send eight 40khz square wave and automatically detect whether it receive the returning pulse signal
 
What's in the box?
1 x HC-SR04 distance sensor
You might need a bracket to mount this sensor
Resources
Follow this tutorial at ThePiHut.
https://thepihut.com/blogs/raspberry-pi-tutorials/hc-sr04-ultrasonic-range-sensor-on-the-raspberry-pi
Using GPIOZero