The VCNL4010 sensor is a nice way to add a small-distance proximity sensor to your microcontroller project. For longer distances (in the range of cm, you can use a SHARP IR distance sensor, but those are only good if the object is over 10 cm away. The VCNL4010 is designed for much shorter distances, no more than 200mm (about 7.5") and under our experimentation we found it worked best at distances of about 10-150mm. It would be good for say detecting when a hand moved nearby, or before a robot smacks into a wall. The sensor also has an ambient light sensor built in.

The sensor uses an infrared LED to bounce light off objects in front of it and gauge the returned intensity.  You could do all this yourself with LEDs and light sensors, but the VCNL4010 wraps all that logic up into a stand-alone chip for you!  With the VCNL4010 you can easily read the proximity (i.e. if an object is near or far) and even ambient light level over a simple I2C connection. 

Best of all the with a CircuitPython module you can use the VCNL4010 from Python code!  This guide shows how to connect and use the VCNL4010 with a CircuitPython or Arduino board.

This sensor is easy to use with any microcontroller that has i2c capability. It is 5 volt compliant so you can use it with 3.3V or 5V logic with no risk of damage. There is an onboard 3.3V ultra low dropout regulator so you can power it with 3.3 to 5.0V. However, if you can give it 5.0V that is ideal since the VIN voltage powers the IR LED and the higher the voltage you can give it, the more powerful it is.