Ultrasonic Proximity Sensors In IoT Context (Raspberry Pi + Windows 10 IoT Core)

Although the Internet aspect of IoT has changed a lot for those small embedded projects, the core of IoT is still largely sensors and embedded components, and the sooner we (the non-embedded developer community) are familiar with all these sensors, the better for the community, IoT, and us. Today, I will talk about Ultrasonic sensors and using them with Raspberry Pi to build a small IoT device that can quite accurately measure distance. This could have a great set of applications such as in smart cars, in automation, in storage and logistics and so on. First, how does the Ultrasonic sensor work? It’s quite simple. You send a high to low pulse to the sensor’s trigger pin with 10 microsecond intervals, this invokes 8 ultrasonic pulses from the sensor. The echo of these pulses is received on the echo pin. The echo pin is set to high for the time it took for the echo to return. So it is quite simple, trigger the sensor, and listen to the echo pulse. As soon as the echo is high, see how long it was set to high. Then, convert this time to distance with the help of speed of sound. (Ultrasonic waves travel with an approximate speed of sound and cover twice the distance, once from the sensor to object, and then the echo of the same. So you need to divide it by 2) you can do the calculation is you like, but I will save you some time, and give you the direct formula in a short while. So, now we know how to calculate distance from the UT sensor. However, there is a catch. Ultrasonic sensor needs 5V VCC. This 5V is returned on the Echo pin to the Raspberry Pi. However, all the GPIOs on Pi are designed to receive 3.3V. Because of this, you should build a voltage divider circuit between the echo pin and GPIO of Pi. Here is a diagram of the voltage divider circuit and a photo of how I built it on a breadboard. Input voltage is by default 5V. Resistor R1 and R2 has to be chosen in such a way that Output voltage V2 should be,