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HC-SR04 Ultrasonic Module User Guide
Hc sr04 ultrasonic distance sensor can be used to measure the distance by detecting ultrasonic rays. Get hc sr04 ultrasonic distance sensor at ELECFREAKS.
Open Source Laser Projection Keyboard
If you want to make and have a cool laser virtual keyboard at low cost, ELECFREAKS' "Open Source Laser Projection Keyboard" may give you a lot of help, click now to learn more