{"id":8185,"date":"2021-10-05T08:10:41","date_gmt":"2021-10-05T12:10:41","guid":{"rendered":"https:\/\/dronebotworkshop.com\/?p=8185"},"modified":"2023-04-12T17:57:19","modified_gmt":"2023-04-12T21:57:19","slug":"waterproof-ultrasonic","status":"publish","type":"post","link":"https:\/\/dronebotworkshop.com\/waterproof-ultrasonic\/","title":{"rendered":"Waterproof Ultrasonic Sensors"},"content":{"rendered":"\n

\"Download \"Parts<\/a> \"View<\/a> \"Download<\/a><\/p>\n

Today we will take a look at a couple of ultrasonic distance sensors that are suitable for outdoor use.<\/span><\/p>\n

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Unlike the ultrasonic distance sensors we\u2019ve used previously, these devices are waterproof.<\/span><\/p>\n

Introduction<\/span><\/h2>\n

We have used the HC-SR04 Ultrasonic Distance Sensor many times here in the DroneBot Workshop<\/a> and for many good reasons. It is pretty easy to use, it performs well, and it is very inexpensive. For collision avoidance robots or intruder detection, this sensor is usually all you\u2019ll need.<\/span><\/p>\n

\"Waterproof<\/p>\n

That is, as long as you are using it indoors.<\/span><\/p>\n

However, using the HC-SR04 outside is a different story. It is a pretty fragile device and can easily be damaged by dirt, or even high winds. And, above all, it is not waterproof.\u00a0 Even sealing up its circuit board would not protect it, as the two transducers it uses are essentially just small speaker\/microphones.<\/span><\/p>\n

But have no fear, there are several ultrasonic distance sensors that do indeed work in harsh environments. You can get them wet, and they will still keep working, and they are also impervious to dust and dirt.<\/span><\/p>\n

You can use these sensors to build outdoor robots, detect intruders, or serve as a backup alarm for your vehicle.\u00a0 And while they definitely are not as cheap as the HC-SR04, they are not all that expensive.<\/span><\/p>\n

Let\u2019s take a look at two of these sensors and see how they work.<\/span><\/p>\n

Comparing Sensors<\/span><\/h2>\n

The two sensors that we are looking at today, the JSN-SRT04T and the A0YYUW, look quite different from one another. However, they both use the same principle of operation.<\/span><\/p>\n

How Ultrasonic Distance Sensors Work<\/span><\/h3>\n

If you want a complete description of the operation of ultrasonic sensors, then please check out the article and video I did on the HC-SR04.<\/span><\/p>\n

The operation of these sensors is summarized as follows:<\/span><\/p>\n

Transducers<\/span><\/h4>\n

A \u201ctransducer\u201d is a fancy name for a device that can either convert mechanical vibrations into electrical energy or convert electrical energy into mechanical vibrations.\u00a0\u00a0<\/span><\/p>\n

Two common examples of transducers are microphones and speakers.<\/span><\/p>\n

Ultrasonic distance sensors employ transducers that can work at ultrasonic frequencies, usually 40KHz.\u00a0 Some, like the HC-SR04 or A02YYUW, use a separate transducer to send and receive pulses of sound. Others, like the JSN-SRT04T, employ only one transducer which can serve as either a transmitter or receiver.<\/span><\/p>\n

Ultrasonic Pulses<\/span><\/h4>\n

In operation, the sensor transmits pulses of ultrasonic sound and then listens to see if they get reflected back. If they do, then the time delay between transmission and reception is measured. This time delay can be used to compute the distance to the object that reflected the sound.<\/span><\/p>\n

\"Ultrasonic<\/p>\n

Speed of Sound<\/span><\/h4>\n

To calculate the distance, you first need to divide the time delay in half, as it represents the back-and-forth travel of the ultrasonic pulses.\u00a0 You then multiply the speed of sound, 343 meters per second, by the time delay to see how far the object that reflected the sound is from the transducer.<\/span><\/p>\n

Note that the speed of sound is not a constant, it can vary due to air pressure, temperature, and humidity. It\u2019s possible to use additional sensors to factor that in, as we did in the HC-SR04 article, but we aren\u2019t doing that today.\u00a0 Of course, you could add this feature in your own sketches if you wish.<\/span><\/p>\n

JSN-SR04T<\/span><\/h3>\n

The JSN-SR04T is an interesting sensor in that it comes as a separate printed circuit board and sensor unit. The sensor, which is a single device that acts as both transmitter and receiver, is attached to the PCB using a 2-meter cable.<\/span><\/p>\n

\"JSN-SR04T<\/p>\n

Another interesting aspect of the JSN-SRT04T is that it can be run in six different operating modes.<\/span><\/p>\n

\"JSN-SR04T<\/p>\n

Mode selection is accomplished in two ways:<\/span><\/p>\n